R v Delbridge

THE EXPERT EVIDENCE IN CHIEF

1. The evidence of Judith Perl in-chief was as set out in her written report dated 15 January 2018.
2. In respect of that evidence, I note the following aspects: a) It sets out her expertise, to which there was no challenge; b) She made a series of assumptions, including that the accused had been a cannabis smoker for 49 years, ceasing in early 2017, before the date of the offence of 7 August 2017. On that day, prior to being tested, Ms Delbridge had been at home with her daughter-in-law and son, who were smoking cannabis via a bong while she had a cuppa. She assumed this was for a few hours and that she afterwards had a shower. The assumption was that the last time Ms Delbridge smoked a joint was a month to six weeks before being stopped by Police; c) Dr Perl's conclusion at para 6 of her report was that based on research studies discussed by her, the accused could not have returned a positive oral fluid confirmation above the detection level of 10 nanograms per millilitre (the reading was in fact 80) due to passive exposure and even less likely she could have had a positive result due to passive inhalation. Nor, according to Dr Perl, could there have been any residual THC in the oral fluid due to the previous use of cannabis; d) The only realistic explanation for the positive test was the very recent use of cannabis.
3. The competing report of Professor Weatherby was to the following effect: a) Again there was no challenge to his expertise; b) At para 4 he states he cannot rule out the possibility that the positive result resulted from passive exposure to cannabis smoke during the morning. This view is based on the assumption that the accused had spent several hours in the close company of two people smoking cannabis, using a bong and that she then had a shower and drove a car with one of those people c) In addition to the passive smoking aspect, Professor Weatherby allows for the possibility of cannabis smoke creating residual cannabinoids building up on surfaces, such as furniture, door knobs and water taps, with the suggestion being this may also have been a cause of the positive test. d) He critiques Dr Perl's report and cross-examination of 30 April 2018 and to put it simply, he disagrees with her interpretation of the Dutch Café study. He said the flaws identified by Dr Perl in that report are not correct. The experts disagree with the actual content of this study in its report, in particular the assertion by Dr Perl in cross-examination that the report of the Dutch Café states "the subjects all had zero THC concentrations prior to testing positive at three hours." Dr Weatherby says that is not correct, with the data showing that one of the subjects was positive at two hours. The opinion of Dr Weatherby is that the paper of the Dutch Café shows it is possible to go into a realistic environment of cannabis smoking and come out and be tested and be positive for cannabis, using New South Wales standards of analysis. e) This Dutch Café study is not in evidence, so I am unable to determine for myself whether the Dr Perl or Professor Weatherby view of its contents is correct. f) That it has been shown conclusively that THC can be found in oral fluid after passive inhalation. g) He disagreed with Dr Perl's assertion that: "The only realistic explanation for the positive oral fluid contamination (of cannabis) would have been her very recent use of cannabis." h) Professor Weatherby could not positively exclude either passive exposure to cannabis smoke or contamination from surfaces as causing the positive.

The Appellant's evidence

1. Ms Delbridge's evidence was that she was 62 years old and that on the day she was tested, was travelling from her house in her car with her daughter‑in‑law. Before doing so, she had spent time, some two hours having a cup of tea with her son and daughter-in-law who were smoking marijuana. She was expressly asked if she smoked any marijuana and said no she did not.
2. She said she had smoked marijuana for about 48 or 49 years, but stopped "last year", meaning 2016 but then said "February", meaning presumably 2017, when she got a good behaviour bond and since then, had a couple of joints between February to August and last smoked six weeks to a month before the test giving rise to these proceedings occurred.
3. The appellant then gave this evidence: "Q. Now what's your understanding Ms Delbridge or what was your understanding at the time in relation to how long you would have to wait before driving after smoking cannabis to make sure there was none in your system? A. I wouldn't have driven my car if I had a smoke, marijuana because I gave that up so I could keep my licence and if I had a smoke, I would not have been driving my car, so I just thought I was okay to drive. So when I got pulled over I got swabbed and it was positive, then when I came back to the station it was negative and it came out of the machine, then they sent it away, it came back positive. So I was shocked that it came back positive because I thought it was okay."
4. Shortly after that there was this evidence: "Q. At that time, did you think that being around other people smoking cannabis, that that could go into your system at all? A. No, I didn't think about that one, I didn't think about it, no I didn't."
5. In cross-examination, Ms Delbridge confirmed that she had sat around for probably a couple of hours having a cuppa and chatting whilst others there smoked marijuana. It was never put to Ms Delbridge that she had smoked or otherwise consumed marijuana, nor was the appellant challenged in cross‑examination as to her belief that it was okay to drive. The closest that point was reached was when Ms Delbridge was asked: "Q. Have you ever been stopped for a similar test in the past where you've been sitting around people who had been smoking? Has this ever happened before, you being stopped for a test before where you had been around people who were smoking? A. No. Q. First time? A. Yes."
6. Otherwise the evidence of the appellant was consistent with the assumptions made by the two experts.

FACTUAL FINDINGS

1. The magistrate had the benefit of observing Ms Delbridge give evidence. In the magistrate's reasons, a finding was made that it would be reasonable to expect that Ms Delbridge would test positive to THC "Given the circumstances that Ms Delbridge indicated". That is, the magistrate accepted Ms Delbridge's evidence.
2. Earlier in his reasons, the learned magistrate stated: "Ms Delbridge gave evidence herself on a previous occasion. She confirmed that she was sitting with others around a table who were smoking cannabis in a bong."
3. Thus, with the benefit of assessing Ms Delbridge's demeanour, her version of the facts was accepted. Given the lack of any challenge to her assertion of not having smoked or otherwise non-passively ingesting cannabis, this finding was almost if not certainly, inevitable.
4. My finding of fact on this material, for the reasons just stated, is that Ms Delbridge did not smoke marijuana relevantly prior to undergoing the testing. When I say relevantly, I mean other than within six to four weeks as she conceded and which at no time was suggested would account for the positive test.
5. This means the only explanation for a positive test is that the cannabis entered her system, either by way of passive smoking or possibly by way of contamination in the way described by Professor Weatherby, due to the residue cannabis leaves on surfaces and perhaps more speculatively, on the facts of this case, depending on where the cannabis smoking equipment might be washed.
6. In my view, this second possibility should be rejected, for the reason it was not the way the appellant argued her case, nor was there any evidence on the issue of just what the state of the surfaces in the house were, how often and how much smoking occurred there, nor any evidence of cleaning routines.

Cross examination of the experts AND DISCUSSION

1. On the next occasion Dr Perl gave evidence. She did not add to her statement in her evidence-in-chief, and she was cross-examined. Dr Perl in cross‑examination was emphatic in confirming the views expressed in her report. In the process, she dismissed other expert evidence that differed from hers as to how long cannabis remained in the system as being "personal opinions and not based on the scientific literature that I am presenting".
2. When asked whether there was any possibility that cannabis could be left in the appellant's system or detectable in her system from the lengthy 49 years of cannabis use or use within one month to six weeks, she stated: "There is no possibility whatsoever based on the scientific literature". This was a reference to THC being in the blood. In relation to the oral fluid, she said: "And then we talk about the oral fluid. There is no study that has demonstrated any THC in oral fluid that can occur as a result of use from months ago or weeks ago or even days ago, because cannabis does not pass from the blood back into the oral fluid in any significant amount. It is the residual of cannabis that is in the mouth or that is being tested by oral fluid."
3. When asked about studies as to oral fluid testing as a result of passive smoking, there was reference to the Niedbala testing. It involved less than ten people as the passive sample, which was in fact a sample of four. Her evidence was that the smokers smoked for 20 minutes and then oral fluid was collected at 45 minutes and again at 60 minutes (I presume from non‑smokers).
4. Following this, it was put that the total period of exposure to the cannabis smoking was 20 minutes, to which there was this reply: "Look I don't know. I've got to read it again exactly what the time intervals were. They're saying that they tested all the first 45 minutes and then they were allowed outside the van after 60 minutes and then continued collecting samples. It says up to eight hours - sorry up to 72 hours."
5. The following question made it clear, that which was with respect clear from the beginning, that the exposure was only for 20 minutes. That is clearly a point of distinction from the facts of the present case. Reference was then made to another study but again with exposure only for 20 minutes and with only a handful of participants, some of the subjects tested positive but at a level below the cut-off level in New South Wales, which I understand to be a reference to ten nanograms.
6. Dr Perl's point was that based on those results, you would get a negative in New South Wales testing because the samples were positive, but at a level below the cut-off point. Self-evidently, the study also shows that it is possible by way of passive smoking to take in sufficient THC to register a reading of some level on an oral fluid test.
7. Dr Perl then referred to a study by Huestis and Cone and confusingly seems to say that that does not relate to passive smoking, but also concluded that you had to have been a frequent user to get a positive result. The question is then sought to return to the passive smoking issue, which led to a reference to the Dutch coffee shop study. In relation to this report, she stated she would not refer to it if she had the choice, which I take to mean a fairly dismissive approach to it. Dr Perl acknowledged that other people who have given expert evidence have raised that study. Dr Perl says it was problematic because in one of the locations there were no active smokers in the coffee shop for two hours out of three.
8. This is an assertion that Dr Weatherby contests. In any event, it does appear that there is other expert opinion in this area which does hold this report in a different regard than Dr Perl. With this last study, there was again a very low number of the sample, being five passive smokers in each of the two locations. This study shows a passive smoker is testing positive, though only to about six nanograms not long after. However, a concession was made that in one of the locations, two of the other subjects in the small room showed more than ten nanograms, one being a 12 and the other 17 and with the passing of time, it appears that returned to zero and this was with exposure of less than one hour. Dr Perl's point is that the report does not show how soon before the testing the exposure occurred.
9. The magistrate had the advantage of observing Dr Perl. My view of her evidence, reading the transcript, is that she is a very dogmatic witness and expert. By implication, the magistrate rejected her evidence for he said: "While I accept the differences between Professor Weatherby and Dr Perl, accepting Professor Weatherby's evidence I am satisfied that as he said in the question that I asked, it would be reasonable to expect, given the circumstances that Ms Delbridge indicated, that she would test positive to the THC and while she had I agree an honest opinion, I am not satisfied it was reasonable, given those circumstances and the offence is proved."
10. It is not clear what the magistrate meant when he said he accepted the differences between the experts. It may simply mean that he is acknowledging that they have differences and he then goes on to accept Professor Weatherby.
11. Given that Dr Perl's clear evidence is that it is impossible for the appellant to test positive by passive smoking and given that the found fact is that she did not smoke marijuana so that the most likely way that she was able to test positive was while passive smoking, it must be that Dr Perl is wrong.
12. In his oral evidence-in-chief, Professor Weatherby referred to a number of studies that have not been referred to by Dr Perl. He disagreed that there were any flaws with the Dutch Café study. In his cross-examination, he emphasised that there was little research into passive smoking. He referred to the need for more data.
13. He gave something of a discourse on the need to measure THC acid in addition to THC so as to avoid false positives. He also referred to the possibility, if not likelihood, that the circumstances of the testing are different to the reality, specifically the possibility of higher doses in reality and less healthy people in reality than the sample.
14. Professor Weatherby considered Dr Perl totally wrong in saying that THC does not transfer from the blood into the oral fluid. It emerged that the study that Professor Weatherby was referring to, the Berthet report, was in fact a review of 159 studies with the review itself being peer reviewed. One criticism of Dr Perl by Professor Weatherby was the limited amount of studies that she had referred to.
15. At the conclusion of Professor Weatherby's cross-examination, the magistrate asked the following questions: "Q. The scenario used, you've got a person sitting around two other people who according to this, sat around a couple of hours quite close to two people using a bong? A. That's my understanding, sorry. Q. On your evidence, there is a reasonable expectation that she would test positive? A. Yes, that cannabis would be found in the oral fluid, yes."
16. On one view, all of the expert evidence in this case has a difficulty because none of the different reports that both experts were referring to were tendered in evidence or form part of their own reports as annexures. For this reason, as Powell J observed in Makita v Sprowles (2001) 52 NSWLR 705 at 708: "It is not possible to know whether what the experts write in their reports as to the contents of other reports was either accurate or complete and further, whether the views they each express are validated or invalidated by those reports."
17. The task however is made straightforward in this case, given my observation above, namely that the proven facts of this case which I find of the appellant not having actively smoked cannabis for a month to six weeks and yet the appellant was able to return a positive result. On the facts as found by me, this positive result occurred due to passive smoking of cannabis. This disproves Dr Perl's opinion.
18. Professor Weatherby's view also has the support of a far more wide‑ranging collection of studies, albeit that the report suffers from the defects stated by Powell J, which is a defect common to both reports. Further still, whilst both experts appeared particularly combative, I was more impressed by the presentation of Professor Weatherby so far as I could ascertain it from the transcript. I am comforted in this conclusion, given the acceptance of Professor Weatherby by the magistrate who observed him.

THE APPELLANT'S CASE

1. The appellant's case is the same now as it was in the Local Court. In short, she says she had an honest and reasonable belief that she would not test positive, because she had not actively smoked marijuana. The magistrate accepted that Ms Delbridge honestly believed this and had the benefit of seeing the appellant in the witness box.
2. Furthermore, as the above excerpts of the evidence demonstrate, Ms Delbridge was not challenged on this issue. What the magistrate was not satisfied about was that the belief was reasonable. He founded this conclusion on the fact that in the view of the expert Professor Weatherby, there was a reasonable expectation that she would test positive if she had sat around with two other people using a bong for a couple of hours.
3. One problem with the question posed by the magistrate or the use of the question in that way by the magistrate is that the magistrate appears to have taken that answer and applied it to the mind of the appellant. My view is that Professor Weatherby was stating that it is his reasonable expectation that the appellant would test positive.
4. Unlike the magistrate, I do not attribute to the state of mind and reasonableness of approach of the appellant, the expert views of Professor Weatherby. For present purposes, the law of honest and reasonable mistake of fact can be shortly stated. An honest and reasonable belief in a state of affairs which, if they existed, would make the defendant's act innocent, affords an excuse for doing what would otherwise be an offence; Proudman v Dayman (1941) 67 CLR 536. It is also briefly discussed in Butterworths Criminal Practice at [13-S54.15].
5. The authors of the Butterworths or Lexis Nexis service note a defendant bears an evidentiary onus to raise the defence of honest and reasonable mistake. Once the defence is raised, the onus then lies on the prosecution to prove that no such belief was held by the defendant and the prosecution bears that onus to the standard of proof of beyond reasonable doubt.
6. This "defence" was discussed in Ibrahim v R [2014] NSWCCA 160. Relevantly at para 54, the two aspects of the situation were commented on, namely firstly that there is an evidential burden on an accused to establish such a belief. The second is that once the burden is satisfied, the onus is on the Crown to prove beyond reasonable doubt that the accused person did not honestly on reasonable grounds hold the requisite belief.
7. The Crown argues that I should accept the opinion of Dr Perl. In short, that opinion was that a positive oral fluid result for cannabis is not possible as a result of passive smoking. On the other hand, Professor Weatherby expressed the view that a positive result could be achieved without smoking cannabis directly and referred to passive smoking in contact with other contaminated surfaces. For the reasons stated above, I reject that Crown submission.
8. The Crown also argued that if Professor Weatherby is accepted and that the positive test was a result of passive cannabis smoking, then the defence of honest and reasonable mistake does not apply where an individual has not formed a positive belief or deliberately considered the action which is later relied on.
9. In support of this submission, the evidence of the offender to the effect of "No I didn't think about that one, I didn't think about it, no I didn't" is relied upon, when asked about whether she considered the possibility of passive smoking leading to a positive test. As is pointed out above, that is not the totality of the evidence in this regard.
10. My view is that the evidence given by Ms Delbridge as set out by me at the beginning or towards the beginning of these reasons, is sufficient to satisfy the evidentiary onus upon the defendant. By that evidence, she asserts that she thought it was okay to drive and was not challenged about that and it was evidence given under oath and it can be concluded to raise the issue that it was honest.
11. As to whether it was reasonable, she held the belief that she did because it had been six weeks to a month since she had smoked marijuana. See the answer preceding the passage just quoted. When the whole of the appellant's evidence is taken into account, namely that she had not smoked in the way she previously had since she got a good behaviour bond in February so she could keep her licence, what is clear is that she believed that if she did smoke cannabis, she would not test positive.
12. The question and answer relied upon by the Crown where the answer is "No I don't think about that one, I didn't think about it, no I didn't" does not in my view counteract the balance of the evidence and certainly not to the extent of negating the evidence from satisfying the evidentiary onus. In finding that the evidentiary onus is satisfied, I take into account that the appellant gave evidence on oath and was cross-examined.
13. This is an important point of distinction on the authorities. In CTM, referred to at para 60 of Ibrahim, the High Court noted that the appellant had not given evidence and there was nothing to support the honesty or the reasonableness of the belief. That is not the position here.
14. Put more simply on the issue of reasonableness, the evidence amounts to saying the appellant did not consider she would test positive by having been in the presence of cannabis smoke, because she thought it was necessary to actually smoke it to test positive. Does this satisfy the evidentiary onus to raise the defence of reasonable belief? More simply still, she did not think she would test positive because she had not actively smoked marijuana. As already noted, my view is that satisfies the evidentiary onus.
15. I note that there have been some cases concerning the length of time a person has stopped smoking marijuana before being tested and the question has been raised as to whether it was reasonable to then drive within a certain period of time. In those cases, there have been issues raised as to what inquiries a person may have made in order to assess the reasonableness of their belief.
16. In my view, those cases do not assist on these facts because it is not an issue as to the passing of time due to the four to six week period that has been stated and the type of test being an oral fluid test. In my view, to establish reasonableness, it is not necessary for the appellant to have carried out any form of investigation or testing in the circumstances of this case.
17. Applying a common sense approach in my view, it is reasonable to be of the belief that there is not the illegal substance in your blood when you have not actively consumed that drug. The argument for the accused is that Professor Weatherby satisfies the evidentiary onus on the accused to the effect that passive smoking can lead to a positive result and that the report of Dr Perl should not be accepted as proving beyond reasonable doubt that is not the case.
18. The second element of the accused's argument is that she had an honest and reasonable belief that she could not test positive by reason of passive smoking. In my view, this is simply putting the question that I have already posed above and answered in a different way. The appellant did not think she had the substance in her blood, because she had not actively smoked it, which in my view is no different than saying because she had only been present when it was being smoked.
19. There is of course a degree of irony in the Crown case in this matter. I say this for the following reason - the Crown now relies on the evidence of Professor Weatherby. In fairness to the Crown, they have not sought in their submissions, as I understand them, to adopt the approach of the magistrate.
20. Furthermore in this regard, the fact that Dr Perl's evidence has been rejected by two Courts after having been examined by numerous lawyers, does not eradicate the fact that Dr Perl is an expert of an unchallenged expertise, who is firmly of the view that it is impossible for the appellant to have tested positive by reason of passive smoking.
21. The evidence that I have just referred to of Dr Perl shows that there is a body of expert opinion that held the same belief as Ms Delbridge did, namely that she could not have tested positive unless she smoked the drug. Whilst Ms Delbridge did nothing to suggest that she was aware of those matters, it supports the common sense approach that I have adopted.
22. The appellant having raised the defence of honest and reasonable mistake of fact, it now falls upon the Crown to prove beyond a reasonable doubt that the appellant did not have that honest and reasonable belief. The question posed by the magistrate is the wrong one with respect to him, for he concluded that the appellant had not satisfied him that her belief was reasonable.
23. In my view, for the reasons above stated, it is well arguable that the belief was reasonable and the evidentiary onus is satisfied. When the question is asked has the Crown proved beyond reasonable doubt that Ms Delbridge did not have that honest and reasonable belief, the answer must be that there is a reasonable doubt. She had never been tested after passively smoking before and the Crown has not led any evidence to show that her belief was not reasonable, nor was she seriously, if at all challenged about that. Indeed, the evidence led by the Crown of Dr Perl supports the view that it was reasonable.
24. For the above reasons, I make the following orders: 1. Appeal against conviction upheld. 2. Set aside conviction and orders of the Magistrate. 3. The appellant is found not guilty and is discharged.

DISCLAIMER - Every effort has been made to comply with suppression orders or statutory provisions prohibiting publication that may apply to this judgment or decision. The onus remains on any person using material in the judgment or decision to ensure that the intended use of that material does not breach any such order or provision. Further enquiries may be directed to the Registry of the Court or Tribunal in which it was generated. Decision last updated: 30 August 2019