Criminal law and procedure - evidence - Evidence of DNA analysis from samples of blood taken from accused - contention that first sample not given voluntarily and second sample taken when accused not lawfully in custody - challenge to record of interview on ground of lack of voluntariness or that evidence of interview should be excluded in the exercise of discretion - all impugned evidence admitted - first blood sample given voluntarily - second blood sample taken lawfully pursuant to 5.81 of Summary Offences Act - no defacto arrest - statement by accused during interview voluntary - no reason to exclude in the exercise of discretion. Summary Offences Act 1953ss.78, 79a, 81; United States v Baller (1975) 519 Fed. 2d 463; R v Gilmore (1977) 2 NSWLR 935; Frye v United States 293 F 1013 (DC Ar 1923); R v Lewis (1987) 29 A Crim R 267; R v Tran (1990) 50 A Crim R 233; R v Lucas (1992) VR 109 and The Queen v Conley (1902) 30 SASR 226. Chamberlain and Anor v The Queen (No2) [1984] HCA 7; (1984) 153 CLR 521 at 598; The Queen v Duke (1979) 22 SASR 46; Comm. for Govt. Transport v Adamcik [1961] HCA 43; (1961) 106 CLR 292; The Queen v Bonython (1984) 38 SASR 45 at 47; Clark v Ryan [1960] HCA 42; (1960) 103 CLR 486; MacPherson v The Queen [1981] HCA 46; (1981) 147 CLR 512; The Queen v Attard and Mifsud (1970) 1 NSWLR 750 at 756; The Queen v Gessing (1985) 38 SASR 226 at 232 and The Queen v Conley (1982) 30 SASR 226 at 239, applied. The People v Castro (1989) 545 New York Supplement 2nd Series 985, discussed.

Counsel for DPP: Ms W J Abraham with Mr S K Mcewen

Solicitors for DPP: Director Of Public Prosecutions

Counsel for accused: Mr G F Barrett with Mr R N H Mayne

Solicitors for accused: David Stokes and Associates

ORDER Publication of reasons for rulings given at trial.

JUDGE1 MULLIGHAN J The accused was charged with the murder, on Saturday 4th January 1992, of an elderly woman, aged 75 years, who was living alone in her own house. Prior to the commencement of the trial he sought the exclusion of the evidence of DNA analyses or profiling of various samples of blood and semen and of the statistical interpretation of such analyses, of the taking of a sample of blood from him at the request of the police on 22nd April 1992, of statements made by him when questioned by the police on 15th July 1992 and samples of hair and blood taken from him after his arrest on that day. A lengthy voir dire enquiry was conducted at the end of which I ruled that the impugned evidence was admissible and that there was no reason to exclude any of the evidence in the exercise of discretion. I intimated that I would publish reasons for these rulings after the conclusion of the trial and I now do so.

The deceased was last seen alive by a neighbour between 11 am and 11.30 am on Saturday, 4th January 1992. She was found dead by neighbours in the back lobby of her home at a little after 10.00 am on Sunday, 5th January 1992, their having been alerted by her daughter who could not raise her on the telephone. She had been physically assaulted, raped and stabbed and had died of heart failure during or soon after the attack. It is very likely that she was attacked and died on the Saturday. None of the neighbours had seen anyone enter or leave the house at any time on the Saturday and no-one heard or saw anything to indicate that she had been attacked. At the post mortem examination of the body, a sample of the blood of the deceased was taken as well as swabs from the high and low vagina. Tapelifts from the body, the clothing of the deceased and the immediate surrounds were taken at the house before the body was moved and further tapelifts were taken at the post mortem examination. They revealed the presence of hair and spray paint which are of forensic importance but of no significance to the matters in issue on the application to exclude the evidence.

The deceased had her roof cleaned and painted in the latter part of 1991. The accused was employed by the contractor who undertook that work and he did the cleaning in August 1991. The painting was undertaken by another employee later in the year.

During the course of their investigations, the police spoke to various men who were known to have gone to the house of the deceased for various reasons. There were 17 such men, including the accused and his fellow employee who painted the roof. Each of them was asked to make a statement to the police as to his involvement with the deceased and to give a sample of his blood. That request was made of the accused on 21st April 1992 and he attended at the Adelaide Police Station early the next morning. He gave a statement to Detective Modra and then accompanied him to the rooms of Dr Flock, a police medical officer, where a sample of his blood was taken and later sent to the State Forensic Science ("the Centre") for DNA analysis.

That analysis was subsequently conducted by Dr van Daal, a forensic scientist. She also had undertaken DNA analysis of the blood taken from the deceased at post mortem, the semen which had been found on the high vaginal swab and the blood which had been taken from the other 16 men. She concluded that of all of the men who had given blood, only the accused could not be excluded as the donor of the semen. This conclusion was communicated to the police in early July 1992. Because of the type of DNA analysis undertaken, Dr van Daal was also of the opinion that the chance of some person other than the accused being the donor of the semen, and therefore the murderer, was less than one in a million. That conclusion was based upon her knowledge of population and quantitative genetics.

As might be expected, the police investigations focused upon the accused. Detective Modra and other police officers went to his flat on 15th July 1992 and he was questioned at length. The interview was recorded on audio tapes which have been retained and were admitted into evidence on the voir dire. Towards the end of the interview the accused was arrested on suspicion of having murdered the deceased. Before being taken to the Adelaide Police Station and formally charged, he was taken by Detective Modra and Detective Keane in a police car to various places in order to point out to them where he said he had acquired a television set of the same make and model as that stolen from the deceased's house. He was also taken to that house and another house which had been mentioned by the accused. The interview continued during the journey in the police car and at the deceased's house.

After being charged with the murder a medical examination was conducted by Dr Long, another police medical officer, and he took samples of the accused's blood and hair from his arms, chest, scalp and pubic area. These samples were taken to the Centre and examined by appropriate scientists. Dr van Daal conducted DNA analyses of this sample of blood.

Having completed her work Dr van Daal took what remained of the blood samples taken from the accused on his arrest and from the deceased at post mortem, the low vaginal swab, and the DNA extracts taken from the sample of the accused's blood taken on his arrest, from the deceased's blood, and from the semen found in the high vaginal swab to Dr Sajantila in Helsinki, Finland. There was insufficient of the high vaginal swab remaining to take to Dr Sajantila. He is a forensic scientist who specialises in DNA analysis using the same methods as employed by Dr van Daal. He undertook analyses of the various samples and reached the same conclusions as Dr van Daal, except that he did not undertake one of the analyses which she undertook and she did not undertake one analysis which he undertook.

Before turning to the grounds upon which the accused sought to exclude the evidence of the DNA testing and the results it is appropriate to say something about DNA analysis or profiling. Dr van Daal and Dr Sajantila gave evidence on the voir dire. Both are highly qualified forensic scientists specialising in molecular biology and DNA analysis in particular. I had no hesitation in accepting them as suitably qualified and experienced to undertake the analyses and to give the opinions expressed during the course of their evidence. I found both of them to be careful and competent experts and that they undertook their work in this matter with appropriate care, skill and competence. I accepted their evidence as accurate and reliable. I do not think it is necessary for present purposes to recite all of their evidence as to their extensive qualifications and experience.

DNA is the abbreviation for deoxyribonucleic acid which is contained in the nucleus of cells in chromosomes in the human body. It is described as the building block of life and is the material, in most cells, that is the code for each of a person's characteristics, e.g. colour of hair and eyes, and is unique to each person except in the case of identical twins. DNA is consistent throughout the body and so, in the case of a male, the DNA in his blood is the same as in his semen. Each person has 23 pairs of chromosomes, one of each is inherited from each parent. The DNA in each chromosome has two strands which are held together by a pairing mechanisms which are pairs of the bases. There are four different bases called A G T C which behave in a certain way; A always pairs up with T and G with C. There are about three billion base pairs along the strands of DNA and their sequence is responsible for the characteristics of a person. Almost three million sites vary from person to person.

The polymerase chain reaction ("PCR") is a technique which amplifies or copies a small region of DNA millions of times. Only a small number of the bases are looked at by the PCR method. By using this method the type of DNA chosen is very variable from person to person. Once the chosen region is copied up there is produced two DNA fragments from each strand, one from each parent. One is longer than the other and they are separated. The PCR method provides a way of measuring the length of these two fragments which are known as alleles and their size is described by numbers. The two alleles together provide the genotype of a person. The regions which are targeted have names which are designated by where they are found on the chromosome. At the Centre four regions are chosen and are known as HLA DQA1, D1S 80, APO B and YNZ 22. The HLA DQA1 is different from the others. It is a region of DNA which is known as a sequence variable region. It is the same length in each person, but the sequences of bases within it are very variable from person to person. Consequently the analysis establishes the variation in sequence in contrast to the other regions, where the alleles are separated not by sequence but by size. The chemistry involved in detecting the sequence difference is complex but the mechanism used is simple to perform. The alleles are the same size but the bases are in different sequence in different people (which is called sequence polymorphism) and those sequences are detected by the dot blot method. There are six different alleles which can be detected by this method, each with a different sequence of bases. Small regions of DNA are made called "probes" which will detect those differences. The DNA which has been copied up in the HLA DQA1 locus and which contains the two alleles is hybridised. It sticks on to a membrane, in the form of a strip, in a particular region if it has that allele. For instance, if the DNA contains allele 4 it will stick to that place on the membrane marked "4". Then a molecule is tagged on to it which by way of colour detects the reaction, the final product showing dots or blots where the alleles are located. The strips must be interpreted by an expert and they are kept and are available to be read by any suitably qualified person. The numbers given to the alleles are 1.1, 1.2, 1.3, 2, 3 and 4.

With respect to the other regions an agarose gel is used after the copying up process to separate the alleles by size. An acrylamide gel is then used. It also separates the alleles by size but over a much greater range. This process also involves the use of a standard, called an allele ladder, which contains known allele sizes. In each of these three regions there are different known allele sizes. In D1S 80 the range is 14 to 41, in APO-B the ranges 31 to 53 and in YNZ 22 the range is 1 to 12, although there are some larger alleles. The two alleles are each typed against the allele ladder and given a number. By way of illustration the alleles of the deceased in the APO-B system were typed by Dr Sajantila as 33 37 which is her genotype in that region or locus. The acrylamide gel for the APO-B and D1S 80 loci are on a plastic sheet and an ethidiumbromide stain is used to enable the sizes of the alleles to be visualised. The gel with the stain is photographed so that a permanent record of the observation may be kept.

The YNZ 22 locus is also known as D17S5 or D17S30. The process with respect to this locus is a little different from the process with respect to DIS 80 and APO-B. The agarose gel is used, but as the size of the repeat unit is much bigger than in the other two loci it is easy to read the different alleles and the use of an acrylamide gel is not necessary. The DNA in the gel is transferred on to a nylon membrane and a radioactively labelled form of the YNZ 22 is applied which sticks to the locations of the alleles. The scientist then x-rays the membrane to produce an auto-radiovideogram showing the alleles and the allele ladder. A photograph is taken as a permanent record.

The evidence sought to be led is that the accused had the same genotypes in the four loci as found in the semen in the high vaginal swab. His genotype in each locus was different from those of the deceased and from 11 of the other men in the HLA DQA1 locus, the first region analysed. The five men with the same genotype as the accused in that locus each had a different genotype from his, and the donor of the semen, in the D1S 80 locus and therefore were excluded as the donor. This evidence is not the only evidence to be adduced at the trial which, if accepted, would link the accused with the murder, but it is nevertheless evidence of considerable importance in the Crown case.

Initially, the grounds of the application to reject the evidence of the DNA analyses were that the PCR method is new and untried, it has not been accepted as reliable so as to be admitted into evidence, it is highly susceptible to contamination of the samples and the Crown could not establish that contamination had not occurred. However, by the end of the evidence taken on the voir dire the grounds of the application had changed, or at least been refined and fell into a narrow compass. It was not suggested that evidence of DNA analyses per se or by using the PCR method should not be admitted because they had not been accepted as a recognised field of scientific knowledge capable of being the subject of expert testimony. The evidence clearly established that DNA analysis by the PCR method is a proper subject of expert testimony. It has crossed the line between "the experimental and demonstrable stages" Frye v United States 293 F 1013 (DC Ar 1923) and is "part of a body of knowledge ... which is sufficiently organised or recognised to be accepted as a reliable body of knowledge" by relevant scientists, namely molecular biologists: The Queen v Bonython (1984) 38 SASR 45 per King CJ at p.47.

It was contended that the evidence should not be admitted because the processes employed by Dr van Daal in the Centre were not in a state of readiness to be presented to a court. They had not been developed to a sufficiently standardised manner so as to be predictable. Her procedures did not comply with guidelines which were in existence at the time. The work was not done in the way that it should have been done with the consequence that the evidence suggests the results might be unreliable. At all events the jury could not be assured that the results are reliable and consequently the evidence was inadmissible or should be excluded in the exercise of discretion. In support of that argument Mr Barrett contended that evidence of DNA analysis is a peculiar type of evidence in that it is a highly discriminating sort of technique and the jury might well be expected to place very high reliance upon it. The higher the reliance, the greater the care that needs to be taken by scientists in undertaking the work and by courts in admitting the evidence.

Before considering those contentions it is necessary to mention in a little more detail Dr van Daal's involvement with DNA analysis and the PCR method. She obtained her PhD in 1986. Her thesis related to DNA. She was then a Post-Doctoral Research Fellow in Washington University in St. Louis, USA working in molecular biology which is the study of genetics using DNA techniques. There are two techniques in particular for DNA analysis, the PCR method and the RFLP method which stands for restriction fragment length polymorphism. The RFLP method is used in some laboratories in Australia and North America, but there is a tendency to change from that method to the PCR method which is used widely in Europe. The PCR method has advantages because very small samples can be analysed. Dr van Daal first used this method in 1988 and has since used it extensively. After a period of a year or so as a senior research associate in the Department of Biochemistry in the University of Adelaide, she joined the Centre in June 1991 and was the most senior DNA scientist at the Centre. She is now the principal forensic scientist in charge of molecular biology at the Centre. Molecular biology in forensic science is DNA analysis of body samples. The Centre commenced DNA analysis in 1991 and adopted the PCR method in preference to the RFLP method. At that time the correct methodology for the PCR method had not been incorporated in a manual of protocols for use in the Centre. Dr van Daal commenced DNA analysis using the PCR method in criminal cases in about August 1991. By the present time she has reported about 100 times in that type of case. DNA analysis has also been used for other purposes, including parentage cases. Dr van Daal has undertaken work for both the prosecution and the defence in criminal cases in other States. Dr Sajantila is a highly qualified and very experienced molecular biologist who has worked extensively in DNA analysis since late 1986 in Finland and Germany. He was a supervisor in the forensic laboratory of the National Public Health Institute of Finland before moving to Ludwig-Maximillion University in Munich in October 1993. The Institute chose the PCR method as opposed to the RFLP method. His work has included validating the PCR method and I accepted his evidence that the PCR method is widely accepted as reliable in the scientific community.

Dr van Daal's work in this case was undertaken in 1992 and, with respect to fresh analysis in one locus, in 1994. At the present time the Centre has almost completed a manual of protocols for DNA analysis by the PCR method. The Centre is working towards accreditation in DNA analysis by the American Society of Crime Lab Directors, known as ASCLAD, which is a five year process. It has accreditation in other areas of its work and expects accreditation in DNA analysis soon. The manual of protocols is required for this purpose.

Dr van Daal was well aware of the correct PCR methodology when she undertook the work in this case in 1992 and 1994. It was established that not all of those procedures had been set down by the Centre in a manual, however, I accepted the evidence of Dr van Daal that those procedures were well documented in peer review publications which are accepted as reliable by molecular biologists. She was familiar with them and she employed them in her analyses.

Dr Harding was called by the accused on the voir dire. He is also a forensic scientist employed at the Forensic Science Centre. He obtained a PhD in 1971 having undertaken work relating to certain proteins present in hair. Without in any way denigrating his impressive qualifications and experience, it must be acknowledged that he has less training and experience in DNA analysis than Dr van Daal and Dr Sajantila, and indeed, little practical experience in DNA analysis. However, that is no reason, in itself, to reject his criticisms of the work of Dr van Daal. He examined the files of the work undertaken by her which records what she did and the results in considerable detail. He also examined the notes of Dr Sajantila. He claimed familiarity with the manual which has been compiled at the Centre and with the "Guidelines for a Quality Assurance Program for DNA analysis" prepared by Technical Working Group on DNA Analysis Methods ("TWGDAM") and other organisations. He claimed expertise in sound laboratory practice and in DNA analysis by the PCR method. He was not asked to undertake any DNA analysis of the various samples and did not do so. This is not a case of suitably qualified experts obtaining different results from appropriate tests. He was critical of the way some of the work was done by Dr van Daal and recorded by her which, according to him, has some bearing on the interpretation of the typings as reliable results. It is unnecessary for present purposes to set out the detail of that criticism or of the response to it of Dr van Daal. It is sufficient to say that the effect of his evidence was that he could not say that some of the tests were conducted properly because there were insufficient records, he would not have interpreted some of the results as did Dr van Daal and there were occasions when insufficient controls were employed. He claimed that the records as to the movement within the laboratory of the various samples and extractions were deficient and that they did not conform with normal laboratory practices which prevented him, and any other reviewing scientist, from being able to exclude contamination. Some of those alleged deficiencies were said by him to be contrary to the protocols laid down by the TWGDAM and other guidelines. He criticised Dr van Daal's work with respect to each of the four loci and maintained that it could not be said that any of the results were reliable. Dr van Daal rejected all of these criticisms. She explained her procedures in detail and why it was, in her opinion, that Dr Harding's criticisms are without substance. I think all that need be said for present purposes is that, in my view, there was no reason to apprehend that Dr van Daal did conduct her work incompetently or that unreliable results were obtained by her. If I had to decide between the evidence of the two witnesses, I would prefer that of Dr van Daal, but it seems to me that is not the issue on the voir dire.

The accused also sought the exclusion of the evidence of Dr Sajantila of the analysis undertaken by him on the ground that the evidence is not capable of establishing that he employed established procedures. I rejected that contention. True it is that Dr Sajantila's notes were in Finnish but his evidence clearly establishes what he did and there is no reason to suppose that he did not employ the PCR method competently and in accordance with established and accepted practice. It is convenient to mention other evidence which the accused sought to exclude. The Crown wished to lead from Professor Chaseling, a statistician, evidence as to the frequency in the population of the combination of the four genotypes of the accused and similar evidence from Dr van Daal and Dr Sajantila. Professor Chaseling claimed expertise in applied statistics and quantitative genetics which is the area of statistics where data from genetical analyses are put together to obtain quantitative genetic measurements. Dr van Daal and Dr Sajantila claimed expertise in the same field but not to the same extent as Professor Chaseling. A data base has been kept at the Centre which includes the genotypes in the four loci of samples tested since DNA analysis commenced at the Centre and which are regarded as independent. For instance, in paternity testing the genotypes of the child are not independent of those of the parents, so the former is excluded from the data base. Genotypes of Aboriginals have also been excluded in case there is a uniqueness by reason of race. Professor Chaseling examined the data base in each locus and by a series of statistical tests determined the frequency of the combination of the accused's genotypes appearing in the population as less than one in 899,229. Her methodology included testing for independence of the alleles from each other, the genotypes from each other, the use of the product method and the application of a confidence limit of 95%. The tests are complicated and some required the facility of a computer but, in brief terms, what she did was to determine the two areas of independence, the frequency of each allele and each genotype in each locus and then multiply those frequencies with the conservativeness of the confidence limit to produce the result which is, in effect, a quantification of the degree of rarity of the combination the accused's genotypes which, if the DNA analyses are accepted, is the same as found in the semen in the high vagina of the deceased.

The accused called Dr Mitchell, a population geneticist, who queried Professor Chaseling's approach in two respects. His evidence, if accepted, is capable of raising a doubt as to Professor Chaseling's conclusions for basically two reasons. According to him, it has not yet been established that sub-groups within the population do not have DNA profiles which are different from the mainstream of the population, and consequentially the statistical approach of Professor Chaseling may produce unreliable results. He did not assert that such is the case but said that in order to produce conclusions which may be safely accepted, the use of the confidence limit is not enough. A ceiling limit must also be used which, briefly described, is that if the frequency of an allele or genotype in a data base is less than ten percent, it should be given a notional frequency of ten per cent before the use of the product rule. Some support for these views is to be found in a report of the National Research Council, however, they have been rejected in many publications and are rejected by Professor Chaseling, Dr van Daal and Dr Sajantila.

The evidence as to the frequency of the combination of the genotypes in the population is challenged on two broad grounds. Obviously, it should not be admitted if the evidence of the DNA analysis is excluded as then it would be meaningless. However it should be rejected not simply because the differences of opinion by Professor Chaseling and Dr Mitchell could not be resolved by the jury, although, it is said, that may be sufficient reason, but because the evidence of Dr Mitchell should be preferred with the consequence that the opinions and conclusions of Professor Chaseling are unreliable and so much so that her evidence should not be admitted.

As I understand Mr Barrett's argument, a further reason for excluding the evidence of the DNA analysis is that the jury could not resolve the conflict in the testimony between Dr van Daal and Dr Harding, even when considering the evidence of Dr Sajantila. The evidence does not permit a finding that the processes adopted by Dr van Daal, and Dr Sajantila, were not in a state of readiness for reliable analyses or that Dr van Daal did not undertake her analyses in accordance with accepted scientific procedures which are widely recognised as reliable. All that may be said from the point of view of the accused, is that there is a conflict in the testimony between Dr van Daal and Dr Harding about those matters. If I was to decide the matter I would find that both Dr van Daal and Dr Sajantila adopted and applied the correct techniques and obtained reliable results. The procedures employed by them are widely recognised and accepted as reliable. With respect to the frequency evidence, there is no reason to conclude that Professor Chaseling's approach and methodology is wrong and has produced an inaccurate or misleading result and a result which could be inaccurate and misleading. All that may be said, at this stage, is that the evidence of Professor Chaseling and Dr Mitchell is in conflict.

Mr Barrett contended that there is a threshold test which does not involve the exercise of discretion. As I understood the argument, it is this: with respect to the DNA evidence the trial judge should conduct a pre-trial hearing to determine if the testing laboratory substantially performed the scientifically accepted tests and techniques, yielding sufficiently reliable tests to be admissible as a question of fact for the jury. That is the approach taken by Sheindlin J of the Supreme Court of New York, in a case involving DNA analyses, in The People v. Castro (1989) 545 New York Supplement 2nd Series 985. With respect to the frequency evidence a pre-trial hearing should be conducted to establish whether the views expressed by Professor Chaseling are sound. If not, then the evidence should not be admitted. Mr Barrett also referred to some Australian cases which, he contended, supported the existence of such a threshold test.

The starting point is that all evidence is admissible if it is relevant to a fact in issue and may only be excluded if it falls within one of the well known policy grounds for exclusion or within one of the recognised grounds for the exclusion of evidence in the exercise of the trial judge's discretion. Expert evidence is no exception. Once it is determined that expert evidence is relevant to a fact in issue, and there is no reason on policy or discretionary grounds for its exclusion, it should be admitted even though it is contested and there is apparently credible expert testimony to the contrary: Chamberlain and Anor v The Queen (No.2) [1984] HCA 7; (1984) 153 CLR 521 per Brennan J at p.598: "The question whether one body of evidence should be accepted over another is not a question for an appellate court; conflicts of evidence are to be resolved by the jury as the constitutional judge of fact: see per Latham CJ in Hocking v. Bell [1945] HCA 16; (1945) 71 CLR 430, at p 440. The evidence of scientific witnesses does not provide an exception to this rule. As Dixon J said in that case at p.496: 'Scientific evidence, even when composed in part of text-books, is no less matter of fact within the province of the jury than is other evidence, and it is the jury's function to estimate the reliance to be placed on scientific witnesses, however eminent.'

If one body of expert evidence is said not to be credible for reasons advanced by the opposing experts, and the reasons are themselves the subject of testimonial conflict between credible witnesses, it must be left to the jury to say whether those reasons are valid to show that the first body of expert evidence should not be acted on. An appellate court enjoys no special knowledge equipping it to assess conflicts of scientific opinion better than a jury. It may be that the jury is not the ideal forum for debating and resolving such issues, but it is the constitutional forum appointed to determine the facts."

In my view the same approach should be adopted by a trial judge at the voir dire stage. The views of Brennan J are not contrary to those expressed by Gibbs CJ and Mason J at p.558 where they agree with the following observations of Jenkinson J in the appeal to the Federal Court: "Those means of evaluating evidence which the jury enjoys by hearing and watching witnesses, and which are denied an appellate tribunal, could not in my opinion have enabled the jury reasonably to have eliminated the doubt, as to whether the matter tested contained foetal haemoglobin, which a careful consideration of the transcript of evidence and the exhibits raises in the mind. It may be conceded, as counsel for the Crown submitted, that idiosyncracies of manner and voice may undermine confidence in the reliability of a witness. But the evidence of Professor Boettcher and of Professor Nairn claimed the consideration of the jury upon grounds which could not rationally be shaken substantially by those things which the eyes and ears of a jury receive, but which a transcript does not reveal. Each of them was giving his opinion on matters of science within disciplines of which each was a master, and at a level of difficulty and sophistication above that at which a juror, or a judge, might by reasoning from general scientific knowledge subject the opinions to wholly effective critical evaluation. The reasoning by which other expert witnesses criticised the conclusions of Professor Boettcher and Professor Nairn, as well as the reasoning by which the latter two witnesses supported those conclusions and criticised the conclusions of the others, were all matter for the jury's evaluation. But in my opinion no juror could reasonably have failed to acknowledge that, reason as he might, he was not in a position to assure himself of the correctness of a conclusion against the opinions of the two professors to the degree which would eliminate reasonable doubt as to that conclusion."

Of course their Honours were considering, at the appeal stage, whether a particular finding, based upon conflicting expert testimony, could have been safely made by the jury. They made no suggestion that the evidence should have been kept from the jury.

In The Queen v Duke (1979) 22 SASR 46, there is no suggestion of a further threshold test once expert testimony is accepted as admissible. In that case the defence sought to have excluded evidence linking fibres found at the scene of the crime with the victim in the exercise of discretion on the ground that prejudicial effect of the evidence greatly outweighed its probative value which was said to be slight. King CJ, with whom the other members of the Court agreed, said at p.48: "There may be unusual cases in which the judge has reason to fear that the jury will be overawed by the scientific garb in which the evidence is presented and will attach greater weight to it than it is capable of bearing. It is to be remembered, however, that under our system, whatever criticisms of it there might be, the assessment of the weight to be attached to expert evidence, as to other evidence, is the function of the jury. That being the system, a trial judge must assume, in my view, that the jury is capable of understanding that it is not bound to accept the expert evidence, that it is capable of resolving conflicts of opinion amongst the expert witnesses, and that it will not be overawed by the scientific garb in which the evidence is presented to it. It is to be remembered, moreover, that for the purpose of enabling the judge to decide as to the exercise of his discretion the question of weight is to be judged upon the evidence which the prosecution proposes to present. It is not the function of the trial judge to hear conflicting expert evidence as to the significance of the physical evidence in order to determine for himself the disputed scientific issues. To do so would be to usurp the function of the jury."

In my view, admissible expert testimony relevant to a fact in issue and of probative value may not be withheld from the jury. Once the expert testimony is found to be admissible, it should be admitted even though challenged and it is a matter for the jury, properly and adequately directed, to decide in the context of all of the evidence in the case, whether the evidence should be accepted: Commissioner for Government Transport v. Adamcik [1961] HCA 43; (1961) 106 CLR 292. I also refer to the observations of the United States Court of Appeal, 4th Circuit, in United States v. Baller (1975) 519 Fed. 2d 463 cited with approval in R v Gilmore (1977) 2 NSWLR 935 at p 939: "Absolute certainty of result or unanimity of scientific opinion is not required for admissibility. (Every

useful new development must have its first day in court. And court records are full of the conflicting opinions of doctors, engineers, and accountants, to name just a few of the legions of expert witnesses.) ... Unless an exaggerated popular opinion of the accuracy of a particular technique makes its use prejudicial or likely to mislead the jury, it is better to admit relevant scientific evidence in the same manner as other expert testimony and allow its weight to be attacked by cross-examination and refutation ..."

Mr Barrett placed considerable reliance on the decision in Castro. Sheindlin J accepted that there is general scientific acceptance of the theory underlying DNA identification, as he described it, and that DNA forensic identification techniques and experiments are generally accepted in the scientific community and can produce reliable results, but he went on to say, at p.999: "A pre-trial hearing should be conducted to determine if the testing laboratory substantially performed the scientifically accepted tests and techniques, yielding sufficiently reliable results to be admissible as a question of fact for the jury."

Mr Barrett argued that the same procedure should be adopted in this country. Those observations appear to be made in the context of admissibility. If that is so they conform with the obligations of the trial judge in this country where there is a challenge to the admissibility of scientific expert testimony. As King CJ said in Bonython at p.47: "An investigation of the methods used by the witness in arriving at his opinion may be pertinent ... If the witness has made use of new or unfamiliar techniques or technology, the court may require to be satisfied that such techniques or technology have a sufficient scientific basis to render results arrived at by that means part of a field of knowledge which is a proper subject of expert evidence."

However, where the issue is simply whether or not the expert witness did employ well recognised and accepted techniques or undertook the work competently, that is a matter for the jury and there is no purpose in a pre-trial hearing. If Castro is to be interpreted contrary to this proposition it does not, in my view, reflect the law in this country.

I turn to the Australian cases cited by Mr Barrett. In R v Lewis (1987) 29 ACrimR 267 the Court of Criminal Appeal of the Northern Territory rejected identification by allegedly matching bite marks on the base of uniqueness of dentition. Maurice J referred to the observations of Jenkinson J in Chamberlain and went on to say, at p.271: "Forensic evidence, especially if it goes to a vital issue implicating an accused person in the commission of an offence, may often have a prejudicial effect on the minds of a jury which far outweighs its probative value. The jury, being people without scientific training, may often be impressed by an expert's qualifications, appointments and experience and the confident manner in which he expresses his opinions. And yet it ought not be left to such matters alone to provide a foundation for the jury making an assessment of the probative value of forensic evidence, particularly where there are conflicts in expert testimony, or where it is acknowledged that other experts of more or less equal distinction are unlikely to agree. For my part I think that whenever the Crown wishes to rely upon forensic evidence the prosecutor has a clear duty, not just to his client, the Crown, but to the trial judge and the jury to acquaint them, in ordinary language, through the evidence he leads, with those aspects of the expert's discipline and methods necessary to put them in a position to make some sort of evaluation of the opinions he expresses. Where the evidence is of a comparatively novel kind, the duty resting on the Crown is even higher: it should demonstrate its scientific reliability. It is not an answer to considerations that dictate these things be done to say the defence may draw it out in cross-examination; that is an abdication of the Crown's primary function in a criminal prosecution. There is a tendency amongst academics, professionals and others who develop skills in a particular area to mystify their field, often by the use of what seems to the outsider to be arcane language. It is the role of a prosecutor to strip forensic evidence of its mystery so far as is possible; trial by expert must never be allowed to take the place of trial by jury. The inability to articulate the principal tenets that need

to be understood, to describe in ordinary language the methods used and the reasons that point to a particular conclusion, these are the hallmarks of unreliable science and the not-so-qualified expert."

I am unable to regard any of these observations as justifying the withholding of admissible evidence from the jury and I do not think that Maurice J was suggesting that they do. They contain some wise advice to prosecutors intending to lead complex evidence. It is not immediately clear to me how admissible expert testimony to which bears upon an important fact in issue may have a prejudicial effect on the minds of jury which far outweighs its probative value in the relevant sense. As King CJ observed in The Queen v Duke (supra) at pp.47-48: "The prejudice ... must, of course, be a prejudice additional to or distinct from the detriment to the accused's interests involved in the probative force of the evidence."

In order to be admissible, expert testimony must be relevant to a fact in issue and comply with well known preconditions, Clark v Ryan [1960] HCA 42; (1960) 103 CLR 486 and Bonython. Once those preconditions are established, it is difficult to see how the evidence may have a prejudicial effect which far outweighs its probative value and even more difficult to see how that may occur merely because of the type of witness giving the evidence or his or her manner in doing so. At all events no such consideration arises here. The DNA and frequency evidence have substantial probative force and there is no prejudicial effect apart from its probative value.

Mr Barrett also drew attention to R v Tran (1990) 50 ACrimR 233. There the Crown sought to introduce evidence of DNA profiling to establish a connection between the accused and the murder victim whom, the evidence suggested, had been raped before she had been killed. DNA was extracted from various samples and analysed. All tests were inconclusive except one which revealed two identifying bands which were very faint and the subject of conflicting expert testimony. The faint bands appeared to match the DNA profile of the accused. There was dispute among the expert witnesses as to whether the faint bands did exist and whether they were from the accused. McInerney J concluded, after a voir dire examination, that the determination of these matters was for experts and the jury would not be capable of determining the issues without accepting the evidence of one or other of the witnesses called by the Crown. Unlike the present case, it was not possible to repeat any of the tests. His Honour went on to say that there was a danger that the jury would look at the bands as they appeared to be adjacent to those of the accused and subjectively conclude that there was a match. He took the view that they were not entitled to perform that function as it required considerable expertise which they did not possess. He considered the position to be analogous to the position in Chamberlain in that the jury could not safely conclude that the faint bands existed and, if so, matched the profile of the accused. He followed the following observation of Hunt J in an unreported decision in R v Elliott: "If scientific testing in the particular case is unreliable or if it has a tendency to produce a misleading or confusing impression for the jury, or if the weight to be afforded in the results is so minimal as to preclude the jury being satisfied beyond reasonable doubt that the Crown has established the fact which it seeks to prove then clearly I have a duty to exclude it from the jury

• whether it is a result of ruling that the evidence is inadmissible or whether it is excluded in the exercise of my discretion."; and excluded the evidence on the ground that it "would have a tendency to produce a misleading and confusing impression for the jury" and further that they would not be capable of determining the issue raised by the evidence. It appears that he considered that he should determine admissibility on these grounds as a threshold question, but even if he was wrong he would have excluded the evidence in the exercise of discretion. If this interpretation is correct I would respectfully disagree with it. In the present context, there can be no reason to exclude admissible evidence except in the exercise of discretion. The resolution of conflicts in expert testimony and the assessment of the weight to be attached to it is the function of the jury. If there is no reason to exclude evidence in the exercise of discretion, it should be admitted and appropriate directions given to the jury as to how any conflicts in the evidence should be approached and what use can be made of the evidence which is accepted.

Reliance was also placed upon the decision of Hampel J in R v Lucas (1992) VR 109 excluding evidence of DNA testing on the ground that it lacked sufficient probative value compared with its possible prejudicial effect. The accused was charged with murder by shooting the deceased through the heart with a cross-bow and later dismembering the body and burying it in two packages at a beach. A smear of human blood was found on a wall in the garage of the accused's father where it was alleged the dismembering occurred. The blood stain was submitted to DNA analysis. At the trial the Crown wished to adduce evidence of DNA analysis of blood taken from the parents of the deceased in order to establish the blood stain on the wall to be the blood of the deceased or a close relative to a high degree of probability. No tests were undertaken on the blood taken from the deceased as, for some reason, no DNA sufficient to run a test was disclosed in the gel. The experts called by the prosecution and the defence on the voir dire disagreed about conclusions to be reached from the DNA analysis and also as to the statistical interpretation and conclusions which may safely be made from such results as are accepted. Eventually the Crown conceded that it would not seek to have admitted evidence of an expert as to the probability of the blood stain having come from a child of the parents of the deceased, but sought to have the evidence admitted for the purpose of establishing that, by reason of the DNA analysis, the stain was consistent with having come from a child of the deceased's parents. Hampel J took the view that it was difficult to see how a jury could resolve the different views of the various experts and even if it was able to do so, it could not relate the differences meaningfully to any conclusion about the reliability of the tests and the significance of the results. After referring to Lewis, Gilmore and Baller, the acceptance by Gibbs CJ and Mason J of the observations to which I have referred of Jenkinson J in Chamberlain and to the observations of the Royal Commissioner (Mr Shannon QC) concerning the conviction of Edward Charles Splatt as to the danger of a jury translating "consistent with a common origin" into "coming from the same source", he concluded that the objection to the DNA evidence was valid. He said, at p.118: "DNA testing is widely regarded as extremely reliable and discriminating. Its limitations and particularly limits as to the conclusion which can be drawn from the tests are not generally appreciated. The jury has no basis on which it can evaluate the evidence. There is no way the jury can properly weigh the value of such evidence if there is no evidence before it as the frequency of a match in the general population. I agree with Mr Shannon's observations and I think that there is in this case the danger that consistency could assume the colour of identity, or at least of probability."

Careful perusal of the reasons for judgment of Hampel J reveal that there were unsatisfactory aspects of the DNA analyses and the difficulties which arose in the true interpretation of them. There was no evidence as to the frequency in the population of the genotypes said to establish the alleged consistency. I am unable to accept that evidence, even of mere consistency and if the subject of challenge, should not be admitted if relevant simply because the jury may not understand it, may not correctly evaluate it or may misuse it. It is the duty of the trial judge to give suitable directions to avoid any of those consequences. In my view those directions should include a direction to the jury that if they cannot understand evidence they should say so whereupon an attempt to address the problem can be made. Often evidence of mere consistency may be of importance depending upon the issues, e.g. it may be a piece of circumstantial evidence which can establish that an accused is not excluded, which may be of significance, or it may assist in the resolution of other factual issues.

In many cases there will be other evidence, particularly in a circumstantial evidence case, which may enable the jury to safely prefer one line of expert testimony over another. In other cases there may be features of the way in which an expert has approached his or her task or even a matter of demeanour which could be decisive. Those considerations only become apparent at the trial even if they are not apparent at the voir dire enquiry, which in some ways is like a dress rehearsal. However, the stage may be reached when the jury cannot distinguish between conflicting experts or the evidence may be so complex that it cannot be understood by the jury, in which case, if the trial Judge is of that view, appropriate directions should be given to the jury that conclusions against the accused cannot be reached if the jury cannot prefer one line of conflicting expert testimony over another or cannot understand the evidence. In my view, it is no function of the Trial Judge, in advance of the trial, to assess expert witnesses and testimony and withhold evidence from the jury if of the view that the jury could not resolve the conflict or understand the evidence.

I rejected the contention that even though expert evidence is admissible and is of probative value, there is a threshold question to be decided before trial as to whether the evidence should be admitted because it is challenged and the jury may not understand it or may not be able to choose between experts. I accept that there may be circumstances in which expert evidence, like any type of other evidence, may be excluded on the ground that its probative value is slight and is far outweighed by substantial prejudice to the accused if it is admitted. The circumstances in which that discretion falls to be exercised were discussed by Lord Du Parcq in Noor Mohamed v The King (1949) AC 182 at p.192: "... in all such cases the judge ought to consider whether the evidence which it is proposed to adduce is sufficiently substantial, having regard to the purpose to which it is professedly directed, to make it desirable in the interest of justice that it should be admitted. If, so far as that purpose is concerned, it can in the circumstances of the case have only trifling weight, the judge will be right to exclude it. To say this is not to confuse weight with admissibility. The distinction is plain, but cases must occur in which it would be unjust to admit evidence of a character gravely prejudicial to the accused even though there may be some tenuous ground for holding it technically admissible. The decision must then be left to the discretion and the sense of fairness of the judge."

They do not, in my view, include the circumstance where the evidence is admissible but is contested and may be difficult to understand. Such a view denigrates the intelligence and capacity of juries and is contrary to principle. Juries must always receive careful direction as to the correct way to approach expert testimony and how to properly evaluate and use it and there is no reason to suppose that juries will not understand and observe those directions.

Furthermore, I think it is a mistake to assume that evidence will be presented in precisely the same way before a jury as it has been presented upon a voir dire enquiry. Counsel are aware of the need to ensure that evidence is presented in a manner capable of being understood by juries but may assume, perhaps wrongly, that presentation to a judge, at the voir dire stage, does not require the same degree of simplicity. To make a judgment before the trial commences that a jury could not understand evidence or resolve a dispute between experts is, in my view, to make a judgment at the wrong time. That judgment can only be made when all of the evidence in the case is before the jury and then it is a judgment, on a question of fact, for the jury to make, with proper directions.

These observations apply to both the evidence of Dr van Daal and Dr Sajantila of their DNA analyses and conclusions as well as the evidence of them and Professor Chaseling as to the frequency of genotypes in the population. I made no adverse findings against any of the witnesses, including Dr Harding and Dr Mitchell. The jury may accept or reject the evidence of any of them and that is the function of the jury. I merely add that, in my view, the evidence of all of the witnesses is capable of being understood by a jury, which is, I hope, apparent from my description of the DNA and frequency evidence and the issues raised, and there is no reason to suppose that the jury could not resolve any differences of opinion which may arise at the trial.

The evidence given at the voir dire by Dr van Daal and Dr Sajantila, which I accepted, clearly establishes that the procedures adopted by them in the implementation of the PCR method are recognised by the relevant scientific community as reliable and have been developed to the stage whereby the results obtained by them may be accepted with confidence.

The evidence of the DNA analyses and of the frequency of genotypes is of substantial probative value and any prejudicial effect arises from that probative weight. There was no reason to exclude any of the evidence in the exercise of discretion.

I turn now to the objection to the admissibility of the evidence of the taking of the blood from the accused by Dr Flock on 22nd April 1992. The basis of the objection is that there was a lack of voluntariness on the part of the accused in allowing the sample to be taken because of improper pressure which had been put upon him or, perhaps, that the circumstances were unfair to the accused and justified exclusion of the evidence in the exercise of discretion. The starting point, on Mr Barrett's argument, is the considerable latent pressure on all of the 17 men to make a statement and give blood so as to avoid a suggestion that they were involved in this very serious and highly publicised crime with the consequence that the police were under a duty to be absolutely correct in the manner of dealing with them. Mr Barrett argued that there was impropriety towards the accused in two respects, the first in what Detective Modra said to the accused on the telephone on 21st April 1992 and the second in what he said to him in Dr Flock's rooms just before the blood was taken. According to Detective Modra he did not make notes of this conversation on 21st April 1992 but his memory of what he said to the accused is as follows: "My name is Detective Modra from the Major Crime Task Force. I'm ringing up in relation to an investigation we are doing into the murder of a woman by the name of Mrs Pitt who was murdered at Pennington. I understand that you were one of the workmen that attended at the scene and I need to see you to obtain a statement as to what you did there, and the actions you took regarding the repairs. ... I also wish to have a sample of blood taken, which is to be voluntary."

The accused agreed and arrangements were made for him to go to the Adelaide Police Station early the next morning because of his work commitments. The accused's version of this conversation differs from that of Detective Modra but the differences are immaterial. There is no suggestion in the accused's evidence that he did not willingly go to the Adelaide Police Station intending to voluntarily give a statement and a sample of his blood.

The accused met Detective Modra at the Adelaide Police Station the next morning at about 7.15 am. He was taken into an interview room. According to Detective Modra, the following conversation occurred:

"Det Modra David, the reason I have asked you here is to get a statement from you about your work at a house in Sarah Court, Pennington belonging to a Mavis Pitt. Do you remember going to the house? Accused This is the one where the woman was murdered? Det Modra Yes, that's the one. Accused Yes, I remember the house, but it was a while ago I was there. Det Modra Well, all I want to do is get what you did there, how long and other info pertaining to the fixing of a roof. Okay? Accused Yeah, okay. Det Modra I would also like to get a sample of blood from you to check with evidence at the scene. We are taking blood from people who attended at Pitt's place, so you are not the only one to give blood. Also it's purely voluntary. You don't have to give blood if you don't want to. Okay? Accused No, I'll help in any way I can. I'll give blood if you want, that's okay. Det Modra Fine. Well, I'll get started on the statement okay."

Detective Modra then took a statement from the accused which he reduced to handwriting and which the accused, upon request, appeared to read and then signed.

They then went to Dr Flock's rooms which were a short distance away. There was general conversation between them on the way during the course of which Detective Modra told the accused that the taking of the blood would not be too long. He then said, "I take it you still want to give the sample of blood" and the accused replied, "Yes sure". Upon arrival at Dr Flock's rooms the accused was introduced to Dr Flock and, according to Detective Modra, the accused became "agitated", which he later explained as meaning "nervous". Detective Modra became suspicious that the accused might be implicated in the murder. However, he had no evidence upon which to base that suspicion. The accused asked where the sample would be taken from and was told from his arm. The accused said he did not want any blood taken from his arms because he had to go to work and his previous experience was that the taking of blood caused soreness. He said that he had to hold a high pressure hose and "it really hurt" and he did not want to have to go through it again. He went on to say that he had to stand on roofs with the hose constantly and that was why his arm became sore. Detective Modra then asked Dr Flock if there was some other place from where the blood could be taken and he mentioned various places: the arms, fingers, legs and the penis. The accused said he could not have blood taken from his legs because he stands on roofs all day and he would have the same amount of soreness as in his arms. According to Detective Modra, he then said: "'Well, it's up to you, David, this is a voluntary sample. You don't have to give blood, but I would appreciate for you to give a sample.' He said 'Yeah,

well, may be you can wait sometime when I'm not working, on holidays or something'. I said 'Well, that's not really convenient. I had the impression from how you were talking earlier that you had no objections to giving blood'. He said 'I haven't, just not from my arms or legs'."

At the suggestion of Detective Modra blood was taken from a thumb of the accused to which he agreed.

According to the accused, Detective Modra did not relate all of the conversations accurately. On the way to Dr Flock's rooms he asked Detective Modra from where the blood would be taken and he said from the arm. He denied being agitated in Dr Flock's rooms. His version as to what was then said varies in some, but immaterial, respects, from that of Detective Modra except that he says that when he asked if blood could be taken from somewhere else Detective Modra said, "Look you said you'd come down here, now you don't want the blood taken". The accused said that he did not have a problem with blood being taken but not from his arms or legs. According to him, Detective Modra's tone changed to being aggressive. The accused asked Detective Modra that if he wanted blood from his arm could it wait for a few days until he had a day off.

I accept the evidence of Detective Modra as to these events and conversations and reject that of the accused where it differs. I found Detective Modra to be a truthful, reliable and convincing witness. I did not form a favourable view of the accused. I considered him to be a clever young man who understood the issues raised in the voir dire and tailored his evidence to form a factual basis for the arguments being, and to be, advanced on his behalf. Also, it is of significance that notes made by Detective Modra of the conversations challenged by the accused were, at Detective Modra's request, read over by the accused and signed by him on 15th July 1992. I do not doubt that if the accused disputed the accuracy of the notes he would have said so.

The alleged impropriety of Detective Modra is that he did not tell the accused, at any time, that the purpose of the blood test was not only to exclude suspects so as to narrow the focus of the police, but also to provide proof of guilt against the culprit and that his behaviour in Dr Flock's rooms, on the accused's version, was sufficient to create involuntariness on the part of the accused. In my view there was no impropriety on the part of Detective Modra. He made a perfectly open request of the accused for stated reasons. It was made clear to the accused that he did not have to comply. In his evidence the accused acknowledged that he was "quite happy to give blood and to co-operate with the police". His evidence makes it plain that he accurately understood Detective Modra's purpose in making the request. His evidence was: "Q. So, as long as they didn't want to take it from your arm or your leg, you were quite happy to give it from wherever it might be suitable to you. A. That was the understanding that they wanted to eliminate suspects and to do that to take a blood sample. Q. That's why you were happy to give it on your terms. A. Well, I just agreed to give it to them, yes. Q. You voluntarily gave the sample. A. Well, in effect, yes, but towards the end it wasn't so much voluntary as much as to get it over and done with." and later "Q. The situation was if he could have taken it from somewhere else that wouldn't cause such a problem like the arm or leg, that would be fine, so it wasn't as a matter of denying giving blood, just the areas which you wanted it taken from. A. Sounds about right. I don't know exactly what was said, but the context is about right. Q. I mean, that was your attitude. A. How do you mean? Q. Your attitude was that you were quite happy to give blood as long as it wasn't from the arm or the leg. A. I suppose, yes."

Later, in his evidence he said that he did not have any problems with giving a statement and giving blood. At no time did Detective Modra mislead the accused. He treated the accused in the same way as the other men. When he spoke to the accused on the morning the blood was taken, he made it clear that there would be a comparison of the accused's blood with "evidence from the scene". At that stage the purpose of the tests was to see who would be excluded and nothing said by Detective Modra was misleading. There is no reason to suppose that the accused did not give the sample of blood in the exercise of a free choice and, in my view, his doing so was voluntary. The circumstances do not give rise to the conclusion that there was unfairness to the accused in any way. There was no reason to exclude the evidence in the exercise of discretion. For these reasons I ruled that the evidence of the taking of the sample of blood was admissible.

The evidence of the record of interview on 15th July 1992 and the taking of the samples and hair was impugned on the grounds that the statements made by the accused were not voluntary and that, in fact, the accused had been apprehended from the commencement of the interview and that apprehension was or became unlawful because he was not dealt with as required by s.78 of the Summary Offences Act 1953. It was contended that the accused was not in lawful custody when the hair and blood samples were taken from him and the whole of the record of interview and the evidence of the taking of the samples, together with the evidence of the examination and analyses of them should be excluded in the exercise of discretion.

A considerable body of evidence was adduced on this aspect of the voir dire enquiry but I do not think it is necessary to recite all of the factual issues canvassed in the evidence. It is sufficient if I set out the findings which I made and which bear upon the issues raised by the challenge to this evidence.

The police were informed by Dr van Daal of the results of the DNA analysis of the blood taken from the accused and the semen in the high vaginal swab in early July 1992. Those results were that the accused had not been excluded as the donor of the semen but all of the other 16 men were excluded. Meetings were held between police officers and senior staff at the Forensic Science Centre. The focus of the investigation was upon the accused and the police were making various enquiries concerning him. They were aware that the DNA analyses was of great significance unless the accused was one of identical twins. It was proposed to question him on 15th July 1992. He had not previously been questioned about his movements on the weekend of the murder. Detective Modra was to carry out that task in company with Detective Keane. It was likely that the accused would be arrested and charged with the murder unless he was able to exonerate himself when questioned. That much was known to the senior police involved in the investigation. Indeed, arrangements had been made for Dr Long to be available to take the samples if the accused was arrested rather than Dr Flock because Detective Modra was concerned that Dr Flock's earlier reference to taking blood from the penis might be wrongly interpreted in some way as a threat. In my view, he was being unduly cautious and the remark of Dr Flock could not sensibly be interpreted in that way. Also arrangements were made for Miss Tridico to attend with the police officers at the accused's flat to supervise the collection of materials should he be arrested. Additional police officers were to attend to question Miss Kirk, the young woman with whom the accused was then living. Before the police went to the accused's house, they considered it highly probable that he would be arrested.

Detective Modra and Detective Keane went to the front door of the accused's flat shortly after 4.00 pm. Detective Modra again introduced himself to the accused and he allowed the two police officers inside. The other police officers remained in motor vehicles in the street and out of sight of the accused. Detective Modra told the accused that he needed to ask him questions in relation to the murder and that he would like to do so "on an audio visual basis" to record the conversation. The accused agreed. Detective Modra told him that to record the conversation they needed to go to police headquarters in the City. The accused said that he preferred to answer the questions there in the flat and Detective Modra agreed. He then told the accused that the DNA analysis of his blood had not excluded him as the donor of the semen found at the scene of the murder and that his "blood matches to the semen at the scene". The accused said, "That's impossible". The following conversation then occurred: Det Modra: : "Well, that's what I need to talk to you about, going through your association with Mrs Pitt, etc." Accused: "Yeah, I have no worries talking to you." Det Modra: "David, I stress that you are not under arrest. Do you understand this?" Accused: "Yes, of course. I don't want to be arrested." Det Modra: "These questions I will ask you, you are not obliged to answer them, but what you do say will be recorded and may be given as evidence. Do you understand?" Accused: "Yes, I do. Should I get a solicitor?" Det Modra: "If you want one, go right ahead and contact one. We'll wait for him to come here?" Accused: "What do you think?" Det Modra: "It's not up to me. If you feel you want a solicitor present, that's fine. I'll do everything I can to assist you in getting a solicitor?" Accused: "I can't believe this. My blood matched up to the semen at the murder, is that right?" Det Modra: "By DNA testing. I cannot tell you much more, as it is quite complicated, but that is the overall result of the DNA testing." Accused: "Look, I'll answer your questions because I have not done anything wrong, and I'm not worried about getting a solicitor." Det Modra: "David, if you want a solicitor, I suggest you get one." Accused: "No, I won't worry about it. I've got nothing to hide."

There was further conversation during which the accused told Detective Modra about his family and that he did not have a twin brother or sister. Two other police officers were called into the flat by Detective Keane and they took Miss Kirk into a bedroom for questioning. The evidence of the accused as to these events was to similar effect although there are some differences. Most of these differences are of no consequence but, at all events, I preferred and accepted the evidence of Detective Modra which was confirmed by Detective Keane.

The accused claimed that there was one, and possibly two, persons whom he thought were police officers at the back area of the flat shortly after he admitted Detective Modra and Detective Keane to the flat. In cross-examination he said that there was a person at the back door who may have been a police officer or a neighbour. Police officers who went to the flat or the vicinity gave evidence and I accept that none of them were at or near the back door. I found that no police officer was at that location and consequently there was no reason to suppose that the presence of any police officer outside the flat at any time could have given the impression of a de facto arrest of the accused.

The audio cassette recorder was activated to the knowledge of the accused and he was questioned from 4.10 pm until 6.33 pm. Towards the end of this part of the questioning, the accused was arrested on suspicion of having murdered Mrs Pitt pursuant to s.78(2). He was again cautioned and informed of his rights as required by ss.79a(1) and (3). They arrived at the Adelaide City Watchhouse at 8.44 pm. Detective Modra asked the sergeant in charge to arrange for a medical examination of the accused and he did so pursuant to s.81(2) of the Act. It was during that examination that the hair and blood samples were taken. In his evidence on the voir dire the accused acknowledged that he told Detective Modra that he preferred to be questioned at the flat rather than go to the Adelaide Police Station. His evidence as to his state of mind was: "Q. What did you think your situation was, did you think that you could do what you liked or that you had to do something? What was your state of mind? A. It was a pretty, you know, severe blow. They just said that my blood matched evidence at a murder scene and they wanted to question me with regard to that. My impression was that I was - they thought I was involved in the murder and they wanted to ask questions; basically that I had to answer the questions."

As to whether he regarded himself as under arrest before the interview commenced, he said: "Q. I think we have seen in the transcript that there was some conversation on the topic of whether you were arrested or not. Do you agree with that. A. Yes. Q. Do you agree that the gist of it was that, coming at least from Detective Modra, that you were not under arrest, do you remember him saying that. A. Yes. Q. What did you make of that. A. I mean it seemed like a bit of a contradiction, you know, from first saying that your blood matches, then having me questioned and Tina questioned at the same time. It didn't really seem like that I was doing anything apart from answering questions for them."

He went on to say that although Detective Modra had told him he was not under arrest, he had the impression that the police were really saying that they thought he was guilty of the murder and he said that if it was only a few questions he would answer them, but it would all depend upon what happened. If he was going to be arrested he wanted a solicitor present.

I rejected the accused's evidence and accepted the evidence of Detective Modra and Detective Keane as to the conversation between Detective Modra and the accused. In my view the police officers behaved in an entirely appropriate manner towards the accused and there is not even a hint of any impropriety on their part. Detective Modra told the accused why they were there and what they wanted to do. The accused was clearly aware of the serious nature of his position. He was cautioned at a very early stage and was aware that he did not have to answer any questions. He chose to do so. I listened to the tapes and easily reached the conclusion that the accused appeared to be willingly answering the questions and volunteering a good deal of information. There was nothing about his manner of speaking or his demeanour, such as it could be determined from listening to tapes, which suggested that he was not speaking voluntarily and with full understanding of the questions.

In cross-examination the accused said that his impression was that "I basically had to answer the questions he put". He agreed that he had been cautioned and that he understood the caution. His evidence continued: "Q. Your attitude at that stage was, wasn't it, that you were quite willing to answer their questions. A. Well, I agreed to answer the questions, yes. Q. You were quite willing to, you said 'not a problem'. A. I always say that. I agreed to answer the questions they put to me because my attitude at the time was they thought I was guilty of something, and the way that for me to - for them to think I wasn't guilty was to answer the questions. Q. You thought that from your point of view you had nothing to hide, 'I will answer their questions, I will tell them what they want to know'. A. Basically."

Also he acknowledged that he agreed to show Detective Modra and Detective Keane the various locations where he was taken after he was arrested.

All of this evidence demonstrates that the accused freely and voluntarily answered the questions of the police officers and was fully aware of the nature of, and reason for, their enquiries and that he was a suspect. He was cautioned and he chose to answer the questions. The accused participated in the interview in the exercise of a free choice to speak or be silent: MacPherson v The Queen [1981] HCA 46; (1981) 147 CLR 512. Statements which are not shown to be voluntary are excluded from evidence whatever the reason, The Queen v. Attard and Mifsud (1970) 1 NSWLR 750 per Walsh JA at p 756 and The Queen v Gessing (1985) 38 SASR 226 per King CJ at p 232, there was no conduct on the part of Detective Modra or Detective Keane which could have influenced the choice of the appellant so as to render his statements to them involuntary. The Crown established that the accused answered the questions voluntarily.

I also reject the contention that the accused had been apprehended by Detective Modra shortly after his arrival at the flat. A person may be apprehended by a police officer even though formal words of apprehension or arrest are not used: The Queen v Conley (1982) 30 SASR 226 per King CJ at p.239. The words spoken by Detective Modra and his conduct could not have conveyed to a reasonable person that the accused had been apprehended. He was told he was not under arrest. He was asked to accompany Detective Modra to the Adelaide Police Station and he declined. He was not then apprehended. In accordance with the wishes of the accused, the interview took place at the flat. I found that the accused was arrested shortly before the interview at the flat concluded at 6.33 pm. I accepted the evidence of Detective Modra that he did arrest the accused on suspicion of the murder of the deceased as he told the accused. That arrest was lawful. Detective Modra was entitled to take the accused to the various places where he was taken before delivering him into custody at the Adelaide Police Station, in order to complete the investigation of the murder, s.78(2), and he acted in accordance with that power. The accused was delivered into custody and formally charged with the murder before the period of four hours expired. The samples were taken from him pursuant to s.81. The apprehension and the taking of the samples were lawful. There were no circumstances about the questioning of the accused so that the admission into evidence of the interview would be unfair. There was no reason to exclude the evidence of the interview or the taking of the samples in the exercise of discretion.

For these reasons I admitted all of the impugned evidence.