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[2025] NSWSC 1575
Supreme Court of NSW
2025-12-19
Campbell J
Original judgment source is linked above.
Source: NSW Caselaw (www.caselaw.nsw.gov.au). Converted to plain text by ZoeLaw. Not the official version.
Medium Neutral Citation: R v Costa [2025] NSWSC 1575
Hearing dates: 12 December 2025
Date of orders: 19 December 2025
Decision date: 19 December 2025
Jurisdiction: Common Law - Criminal
Before: Campbell J
Decision: On his plea of guilty, the offender, Isaac Costa is convicted of the murder of Anastasiia Slastion and on sentence:
1. a term of imprisonment of 18 years, having the following components:
(a) a non-parole period of 13 years and 6 months commencing on 25 February 2023 and expiring on 24 August 2036, and
(b) an additional term of 4 years and 6 months commencing after the expiration of the non-parole period and expiring on 24 February 2041. You will be first eligible for parole after the expiration of the non-parole period on 24 August 2036.
2. Direct that this offence is to be recorded on Mr Costa’s criminal record as a domestic violence offence in accordance with s 12(2) Crimes (Domestic and Personal Violence) Act 2007 (NSW).
Catchwords: CRIMINAL LAW – murder of an intimate partner – where the offender entered an early guilty plea
SENTENCING – objective seriousness of offending – intention of the offender to inflict grievous bodily harm, not intention to kill – where cause of death due to multiple, possible contributing factors causing death – “unascertained causes” – where the offender inflicted moderate force, not extreme or severe – no history of domestic violence – objective gravity of offending somewhat below middle range
SENTENCING – aggravating factors – murder committed in the offender’s home where the victim resided
SENTENCING – subjective circumstances – where the offender pleaded guilty at earliest opportunity and demonstrated remorse – evidence of prior good character – good prospects of rehabilitation
Legislation Cited: Crimes Act 1900 (NSW) s 19A
Crimes (Domestic and Personal Violence) Act 2007 (NSW) s 12
Crimes (High Risk Offenders) Act 2006 (NSW)
Crimes (Sentencing Procedure) Act 1999 (NSW) ss 3A, 21, 21A, 30A, 54B, 61
Cases Cited: Hoare v The Queen (1989) 167 CLR 348
Jonson v R [2016] NSWCCA 286
Muldrock v The Queen (2011) 244 CLR 120; [2011] HCA 39
Munda v Western Australia (2013) 249 CLR 600
R v McNaughton (2006) 66 NSWLR 566
Category: Sentence
Parties: Rex (Crown)
Isaac Clement Joseph Costa (Accused)
Representation: Counsel:
N. Marney (Crown)
J Stratton SC and B Vasic (Offender)
Solicitors:
Solicitors for Public Prosecutions (NSW) (Crown)
S.F. Legal Pty Ltd (Offender)
File Number(s): 2023/64006
Publication restriction: Nil.
While this matter remained in the Local Court, the offender, Isaac Costa, entered a plea of guilty to the charge that he murdered Anastasiia Slastion at about midnight of 24 and 25 February 2023. On 15 May 2025, he was committed to this Court for sentence.
Upon arraignment before me at the commencement of the proceedings on sentence on 12 December 2025, the offender adhered to his plea of guilty and it is my task to pass sentence upon him.
The facts relevant to sentencing have largely been agreed between the parties and a statement of agreed facts has been tendered (Exhibit 1.3). The narrative of my factual findings relevant to the nature of the offending which follows is largely derived from that statement.
There remains a dispute about the precise medical mechanism of Ms Slastion's death and I received additional evidence relevant to that issue in the form of: Post-Mortem Examination Report for the Coroner by Dr Rebecca Irvine, forensic pathologist, dated 10 October 2023 (Exhibit 1.7); the report of Professor Peter Ellis OAM, forensic pathologist dated 12 June 2024 (Exhibit 1.8); the transcript of expert evidence called in the committal proceedings on 6 September 2024 (Exhibit 1.9); and the report of Professor Johan Duflou, forensic pathologist, dated 15 January 2024 (Exhibit 1.10). I will return to this issue later in these reasons.
Ms Slastion was born in December 1990 and was aged 32 years and two months when she was murdered by the offender. She was born in Latvia but raised in the Russian Federation. She was a Russian citizen.
From the victim impact statement of her mother, Tatiana Slastion, the deceased studied engineering at the University of Information Technology, Mechanics and Optics, St Petersburg and graduated in 2013. Other evidence in the case suggests that her area of expertise was in electronics, and she worked in the information technology industry.
Ms Slastion came to Australia on a working visa on 30 October 2022, having previously holidayed here. From her mother's statement, she was sponsored by an IT company she worked for in Russia, which then relocated its operations to Türkiye before transferring Ms Slastion to Australia. After her arrival, she resided in Surry Hills.
The offender was born in August 1994 and was aged 28 years and 6 months when he murdered Ms Slastion. He had been raised by his parents in the Greystanes region of Sydney, and he continued to reside at the family home in a “granny flat”. Although without formal trade qualifications, through training and experience acquired working in the family electrical business under the guidance of his father, a qualified electrician, the offender had well developed electrical skills. After the closure of the family business, he was able to obtain work in that field for other companies. When his offending occurred, he was in full-time employment as a trades assistant in the electrical construction field.
Ms Slastion and the offender met in January 2023. On his own account which has been derived by me from the report of Dr Olav Nielssen, psychiatrist dated 11 November 2025 (Exhibit A.1) and other sources, the offender had developed an interest in Russia and picked up a smattering of the Russian language through Armenian friends. He and Ms Slastion ‘hit it off’ when he approached her in a bar and addressed her in Russian. They commenced seeing each other, forming an intimate relationship over a period of six weeks leading up to 24 February 2023.
“Police examined the death scene and found bloodstains in multiple locations in the granny flat, including on a sliding door frame, on the floor and walls of the main room, the door leading to the bathroom, on various surfaces in the bathroom, and on the bed and bed head where the deceased was lying. Fragments of teeth were also located on the bed. Defects and areas of damage were identified on the bathroom door. [Ms Slastion’s] body was noted to be bloodstained, and obvious injuries were observed by scene examiners."
From the post-mortem examination carried out by Dr Irvine as summarised in the agreed facts (Exhibit 1.3, par [35]), there were several blunt force, mainly soft tissue, injuries to Ms Slastion’s face and neck. The pattern of injuries suggests blunt force trauma about the face inflicted by the use of the offender’s fists. There was swelling observed by police over the offender’s right knuckles. There were scratch marks on the offender’s neck which may suggest Ms Slastion struggled with him. There was also evidence of asphyxiation of Ms Slastion, probably by neck compression, although Dr Irvine could not exclude occlusion of the outer airways by smothering.
The individual injuries were extensive, involving deep bruising to the left side of Ms Slastion’s face, a haemorrhage of the right eye socket, two black eyes and large petechial haemorrhages in both eyes, often associated with strangulation. There were extensive abrasions to the left side of her face and the bridge of her nose. Three upper teeth were fractured, caused either by blunt force trauma such as a punch or possibly by the exertion of force in an attempt to smother Ms Slastion. And there was a perforation of Ms Slastion’s left upper lip associated with a left upper canine tooth.
In the region of Ms Slastion’s neck, there was a patterned mark to the right front of the neck and extensive external contusions to the left side. At post-mortem examination, there were internal haemorrhages within the structure of the left side of the neck. On an x-ray conducted post-mortem, there appeared a fracture of the left thyroid cartilage, but this was not confirmed by the post-mortem examination.
Testing of Ms Slastion’s brain by a neuropathologist showed staining of the “corpus callosum”' which is suspicious for a component of traumatic “axonal injury”. But definite signs of traumatic brain injury were not found.
Dr Irvine expressed her conclusion as to the manner of death in the post-mortem report (Exhibit 1.7, p 4) in the following terms:
“Both blunt force injuries of the head and asphyxia, are strong possibilities in this case, likely in combination, but there are no definitive demonstrable findings for either. There was no significant underlying natural condition or toxicological cause of death. As such, the cause of death is best stated as "unascertained causes”.
Blood tests from Ms Slastion taken at the time of post-mortem, which are accurate for blood alcohol concentration at the time of death, returned the reading of 0.212g/100ml. Like the offender, Ms Slastion was probably very drunk, even making an allowance for a degree of tolerance or habituation to the effects of alcohol.
The offender's mother also rang police saying, “My son has killed his girlfriend”.
I accept that the offender, as recounted in the agreed facts, made an attempt to take his own life after taking his parents to the granny flat and making another, futile attempt to resuscitate Ms Slastion by chest compression. He began to cry and said, “I'm sorry”. When he returned to his parents’ residence he went to the kitchen and obtaining a knife held the blade towards his neck. He said, “I want to kill myself”. His parents are both older people and struggled with him, attempting to wrestle him to the ground. This was witnessed by the first police officer to arrive on the scene who came to their assistance apparently deploying his taser and handcuffing the offender.
I have said that the offender gave Ms Slastion a valuable gift on Valentine's Day. From the execution of a coronial scene order on 1 March 2023 at Ms Slastion’s address in Surry Hills, the jewellery gift bag was seized and was found to contain a three-page letter from the offender. It is not necessary to set it out in full for the purpose of this judgment. It not only spoke of the offender’s love and admiration for Ms Slastion but also referred to some upset he had caused which had made Ms Slastion unhappy. It is not clear whether this is the same event of which I have previously adverted (at [11]) but given the proximity of Valentine's Day I would infer that it probably constitutes further evidence of the offender’s possessiveness and the apparent emotional volatility in their relationship. There is no evidence of any physical violence inflicted by the offender on Ms Slastion prior to the night of her murder.
“Blunt force injuries of the head, potentially fatal, and findings concerning for asphyxia (neck compression and occlusion of the outer airways) in a young woman with no other cause of death.”
This is consistent with the cause of death appearing in the body of the expert’s report, as I have already mentioned (Exhibit 1.7, p 4). Dr Irvine’s use of the expression “unascertained causes” conformed to the conventions for presenting findings in post-mortem reports for the coroner.
In cross-examination, Dr Irvine accepted that at the post-mortem examination the evidence pertaining to the significant blunt force injuries to the head of Ms Slastion showed “no obvious lethal injury” (23.5T) and that although there was some suspicion of a traumatic axonal injury, there was “not enough to make a definitive diagnosis” (23.17T). Likewise, she agreed that there were no demonstrable fatal findings of asphyxia (23.30-45T). However, Dr Irvine adhered to her view that the combination of those factors caused Ms Slastion’s death and she could not concede on her post-mortem examination findings of any other rational cause of death. She regarded that as “exceptionally unlikely” (24.18T).
In his report, Professor Ellis considered that the neuropathological changes detected in Ms Slastion were “insufficient to unequivocally diagnose traumatic brain injury, despite suggesting that such injury may be present” (original emphasis) (Exhibit 1.8, [5]). Professor Ellis also expressed the opinion the injuries resulting from both blunt force trauma to the head and likely asphyxia following neck compression “may not be individually severe enough to explain death by themselves (although that is not excluded) but in combination it is not unreasonable to consider them the cause of death” (original emphasis) (Exhibit 1.8, [8]). He referred to the significantly elevated blood alcohol reading for Ms Slastion at the time of death and pointed out that alcohol is a cerebral depressant. In that context, the combination of the consequences of blunt force trauma and asphyxia “may be responsible for death” ([8]).
Although the injuries as described in the post-mortem report, and the external injuries as depicted in the restricted Exhibit 3, which I have reviewed for myself sound and appear extensive, from Professor Ellis’s point of view they are "relatively minor areas of bruising… around the face and neck” (Exhibit 1.8, [9]). He stated,
“As such, the injuries themselves would not be the cause of death, but they are indicative or suggestive of the application of blunt force trauma. It is that trauma that certainly may be responsible for death by the causation of brain damage or malfunction of the respiratory system”.
“It is impossible to be definitive in establishing whether either of these two components [of blunt force injury and asphyxia] actually caused death or whether they accelerated death possibly in the context of the other component. In other words, the physical evidence observed at autopsy is relatively minor but may be indicative of more serious physical assault. It is impossible to determine merely by observing these relatively minor abnormalities… whether each was specifically causative of death. The autopsy process and, in particular, the post-mortem report tends to advocate the use of a single element responsible for causing death hence the structure of the death certificate that asked for a “Direct Cause” when it is sometimes not possible to determine which of more than one possible component is principally responsible” (original emphasis).
I take the other component to be the high blood alcohol reading. Professor Ellis expressed the opinion that, “in the context of possible imposed cerebral injury through blunt force trauma together with asphyxia, a significantly elevated blood alcohol content should not be discounted as a possible contributing factor in leading to irreversible brain dysfunction and death” (original emphasis) (Exhibit 1.8, par [10]). Professor Ellis adhered to these views in his evidence at the committal hearing (9.5-43T).
In cross-examination, Professor Ellis confirmed that, in his opinion, the head injury and the likely asphyxia suffered by Ms Slastion may not be enough to explain death themselves. However, because neither were sufficient individually to cause death does not mean that neither contributed to death (16.5T).
Professor Duflou explained in some detail his opinion why, on review of the literature on these matters, neither the head injury nor the asphyxia nor the alcohol intoxication, considered individually, was a cause of Ms Slastion’s death. Interestingly, he was of the view that the blunt force injuries to Ms Slastion’s head do not have features indicative of severe force. He accepted that the injuries were significant but, adopting what he called “a semi-arbitrary scale of trivial-mild-moderate-severe-extreme” to classify force, in his view, the injuries were the result of moderate force. In the absence of lacerations to the scalp, skull or facial bone fracturing, or internal bleeding inside the cranial cavity, death due to head injury would be unusual and not expected.
In Professor Duflou’s opinion, death due to neck compression or external airway orifice occlusion could not be excluded, but the features documented by Dr Irvine at post-mortem were non-specific and were of a type that have been seen in both lethal and non-lethal cases. Concerning the intoxication, Professor Duflou seemed to opine that the level of blood alcohol concentration even in combination with the benzodiazepines and antihistamines detected in the toxicology tests conducted post-mortem were highly unlikely to have resulted in respiratory depression to the extent of causing death or significantly contributing to it.
However, despite the strong expressions of opinion in the final analysis Professor Duflou’s view was much like Professor Ellis’s. He expressed himself in this way (Exhibit 1.10, [26]):
“The reason for [the] difficulty in relation to cause of death is that there is no specific identifiable anatomical abnormality which unequivocally caused death, and it is possible that the combination of factors caused death in this case. Specific issues which need to be considered in detail are the head injuries, the possibility of an asphyxial cause of death, and the role of alcohol”.
There are a number of points I wish to make about this evidence and its significance.
First, the offender has pleaded guilty to murder. Therefore, he has conclusively admitted his responsibility for each legal element of the offence, relevantly including that by his acts of bashing Ms Slastion with his fists and compressing her neck or smothering her external airways he caused her death. Whether or not, in the circumstances, her self-induced intoxication contributed makes no difference. From his plea, the offender’s acts are taken to be a significant and operative cause of death whether or not other factors for which he was not responsible play a part.
Secondly, as I have sought to demonstrate in my analysis of it, the unanimous medical opinion is that while neither of the factors for which the offender is responsible individually was the direct cause of death, each plays a part in combination in bringing about Ms Slastion’s death. Her self-induced intoxication played a part as a contributing factor, but it too was insufficient by itself to cause death. Its part was as a cerebral depressant, leading to reduced respiration during and after the bashing she received at the hands of the offender. In my judgment, the expert evidence establishes that, but for the bashing, Ms Slastion would not have died when and where she did.
Thirdly, as the Crown argue and in light of the opinions of the experts, the force of events and, particularly, the very proximate temporal connection between the bashing and Ms Slastion’s death, persuade me that, were it necessary to so find, absent the offender’s plea, the only rational inference available on the whole of the circumstances established by the evidence before me is that the bashing at the hands of the offender caused Ms Slastion’s death.
Fourthly, causation is determined with the benefit of hindsight. The inquiry is into what happened and why. The existence of a contributing factor for which the offender was not responsible, that is, Ms Slastion’s self-induced intoxication, is not determinative legally. The offender’s acts need not be the sole or direct cause of death and he is required to take his victim as he finds her.
Finally, notwithstanding the nature and multiplicity of the injuries, I am satisfied that they are not the result of the infliction of extreme or severe, as opposed to moderate, force. This consideration is relevant for sentencing purposes in relation to whether the offender intended to kill Ms Slastion as the Crown contend and for the purpose of assessing the objective seriousness of the offending.
It is convenient now to turn to the question of the requisite level of intent for murder held by the offender at the time he killed Ms Slastion. As a matter of law, an essential element of the crime of murder is that the prosecution prove beyond reasonable doubt that when the offender committed the fatal act, he had the requisite actual intention of either killing the victim or inflicting grievous bodily harm upon him or her. For sentencing purposes, an intention to kill is regarded as more serious than an intention to inflict grievous bodily harm or to put it in more modern language, really serious bodily injury.
A plea of guilty to murder does not specify which of those alternatives is applicable to the case at hand. Where, as here, there is a dispute with the Crown contending the requisite intention is to kill rather than an intention to inflict grievous bodily harm, it is for the Crown to prove the more serious alternative for which it contends beyond reasonable doubt.
The Crown accept that the killing of Ms Slastion was neither planned nor premeditated by the offender. It argues that those factors are not essential to a finding of an intention to kill as the requisite intent to kill can be formed spontaneously in the heat of the moment; and an offender may repent of it immediately after the killing. So much may be accepted.
It is the Crown case that the offender’s assault on Ms Slastion was a sustained, extremely violent attack involving punching and strangulation. The offender exerted enough violence upon her to fracture her teeth and cause extensive bruising. The Crown submits that the attack was so violent, and was sustained until death, that the only reasonable conclusion is that it was carried out with the intention to kill, even if the intent was short lived and regretted immediately afterwards.
Mr Stratton SC and Mr Vasic, who appear for the offender, submit that the Crown have not proved that the offender had the intention to kill Ms Slastion. It was submitted that the absence of premeditation tells against that intention. Counsel also point to the absence of any history of violence or threats of violence in the relationship. Indeed, the offender has no criminal history of the commission of other violent offences. There is no evidence whatsoever of any expression of intent or desire to kill Ms Slastion before the events of 24 February 2023. The offender also did not flee or conceal evidence, and the uncontradicted evidence is that he attempted to revive Ms Slastion more than once. The evidence also clearly shows that immediately after the killing and ever since the offender has been extremely remorseful.
Genuine remorse is not necessarily inconsistent with a contemporaneous intention to kill at the time of the infliction of the acts causing death. And it may be said that a brain snap is not inconsistent with the formation of an intention to kill as the Crown argue.
It is necessary for me to make an assessment of the objective seriousness of the offence. It is well-established that the objective seriousness of an offence is to be assessed without reference to matters personal to a particular offender or class of offenders. It is to be determined wholly by reference to the nature of the offence: Muldrock v The Queen (2011) 244 CLR 120; [2011] HCA 39 (Muldrock) at [27].
The assessment of objective seriousness is important for the application of the principle of proportionality in sentencing which emphasises the need for the punishment to fit the crime. For this reason, it has been said that the assessment of the objective seriousness of the offence fixes the upper and lower limits of an appropriate sentence for the case at hand (Hoare v The Queen (1989) 167 CLR 348 (Hoare) at 354; R v McNaughton (2006) 66 NSWLR 566 at [15]). Generally, objective seriousness of the offence is kept separate from the question of the offender’s moral culpability for the reasons I have explained. Objective seriousness is concerned with “the gravity of the crime considered in the light of its objective circumstances” (original emphasis) (Hoare at 354).
In the case of standard non-parole period offences, as murder is, the assessment of the objective factors affecting the relative seriousness of the offence is important for determining whether the standard non-parole period represents an appropriate component of the sentence for the offender (s 54B Crimes (Sentencing Procedure*)* Act 1999 (NSW) (Sentencing Procedure Act).
Neither the Crown nor Mr Stratton and Mr Vasic made an express submission about where in the range of objective seriousness this offence should fall and nor were they required to. However, factors advanced by the Crown in relation to the question of intent are matters which may be relevant to my assessment of objective seriousness. A significant factor is that the murder occurred in the context of an intimate domestic relationship. However I have not accepted all of the Crown’s contentions. I accept that the domestic nature of the relationship between the offender and Ms Slastion is an objective circumstance which informs the assessment. It is also relevant for other purposes of sentencing to which I will return.
Some of the countervailing factors relied upon by Mr Stratton and Mr Vasic in relation to cause of death and intention are also relevant to the assessment of objective seriousness.
I consider that the relevant factors in the present case are that the murder occurred in the context of an intimate domestic relationship, but not one characterised by a history of domestic violence. There was over the short period of six weeks during which the relationship subsisted disharmony and emotional volatility on the part of both and possessiveness on the part of the offender.
“That construction promotes the purpose of the section, namely, that a home is a place which should be safe and secure for persons who reside, or are otherwise present, at such a place. Thus, it would be extended to persons (for example, children) visiting a relative's home or, for that matter, persons in a domestic relationship at the home of the offender”.
Mr Stratton and Mr Vasic submitted that the provision may apply to the home shared by an offender and a victim living together in a domestic intimate relationship, but not the offender’s home when they lived separately and apart.
With respect, I do not accept the defence argument. Grammatically, the provision makes a distinction between the home of the victim, on the one hand, and the home of any other person, on the other. A home shared by the victim and the offender because they were living together would be covered by the expression “the home of the victim”. The provision is to be construed by giving the disjunctive “or” work to do. The provision obviously contemplates the commission of an offence against the person of the victim when he or she is in the home of another person. This would cover the present circumstances.
It is true to say that Jonson was concerned with circumstances involving the offender and victim’s shared home. But it was also a five-judge bench of the Court of Criminal Appeal, and while Bathurst CJ's dictum I have quoted may not be part of the ratio of the case, obviously it was intended to provide guidance to lower courts in future cases.
In the paragraph preceding the passage I have quoted (at [75] above), Bathurst CJ stated, “on a literal construction, this could, hardly surprisingly, include the offender’s home”: Jonson at [40]. His Honour observed that the section was not limited to circumstances where the offender was an intruder either in the victim's home or some other home. Each of the other members of the Court, including Beasley P, Hall, Bellew and N Adams JJ agreed with the Chief Justice.
I conceive that it is my duty to apply seriously considered dicta of the Court of Criminal Appeal as though it were part of the ratio decidendi of the decision, more so when it is unanimous.
I accept the Crown's submission, and I am satisfied that the offending is aggravated by the consideration that it occurred in the offender’s home which was a place where Ms Slastion was entitled to be safe and secure.
Ms Slastion is survived by her mother, Tatiana Slastion, father, her paternal grandparents and her maternal grandmother, all of whom are residents of the Russian Federation. Tatiana Slastion was unable to be present at court during the proceedings on sentence and attended by audio visual link. As she does not speak English, her victim impact statement was written in the Russian language and translated into English when received in Australia. It was not read aloud in court but tendered in accordance with s 30A of the Sentencing Procedure Act. I have read the statement carefully, and as Ms Slastion was a member of the Australian community when she was murdered, I will take the impact of her death on her family into account as an aspect of the harm done to the community as requested by the Crown.
From the victim impact statement, it is apparent that Ms Slastion was a clever, talented and creative child, and these attributes continued into her adulthood. Although she had worked away from home in Türkiye, before moving to Australia, for about two years prior to her death, she kept in touch with her mother by telephone and letter.
Tatiana Slastion has lost her only deeply beloved daughter. She feels her joy and happiness has been taken away from her and that she has no future. She described her daughter as the light of her paternal granny and grandad’s lives. She was their only granddaughter. She was adored by her maternal grandmother.
The family received the news of Ms Slastion’s murder via Interpol. Tatiana Slastion said, “at first, we just couldn't believe this nightmare”. It took some time for them to receive confirmation of the tragic news. During that time, Tatiana Slastion could not eat or sleep and felt only her father-in-law had been able to help her.
Due to legal formalities, Ms Slastion’s body was only returned to her family two and a half months after the murder. For this reason, they had been advised not to have an open coffin for her funeral, as is the Russian Orthodox tradition. Tatiana Slastion and other family members felt that for this reason they have not been able to say a proper goodbye to Ms Slastion.
On behalf of the Court, I offer my condolences to Ms Slastion’s immediate and extended family, especially her mother.
Tatiana Slastion has expressed a preference that, for privacy reasons, her victim impact statement is not made available for publication. Victim impact statements form a special category of evidence in the criminal process and differ from the other evidence received for the purpose of sentencing the offender. I will respect Tatiana Slastion’s wishes in this regard.
As I have already said, the offender was born in August 1994. He is the youngest of three siblings born of his parent’s union. He has an older half-sister from his father's previous marriage. He had the considerable advantage of being brought up in a loving, respectable and hard-working family.
His mother describes him as a gentle person, kind, considerate and hard working. His father said he had never known him to be aggressive in any way.
As I have said, he was raised in the Greystanes area and attended the local primary and high schools. He experienced learning difficulties as a child which were not entirely overcome even with the intensive assistance of his mother who attended his primary school every day to help him.
As I have already indicated, his father was an electrician with his own business, and the offender left high school at the age of 15 without obtaining his school certificate to work in the family company with his father and older brothers. After his father's retirement, the family business was conducted by the brothers but regrettably, for reasons I need not expand upon, it was later wound up in insolvency. However, the offender continued to be hard-working and conscientious, working for other employers mostly in the electrical field in which he has acquired valuable experience.
A reference from the project manager of his current employer as of the date of his arrest speaks very highly of him as a valuable, contributing and hard-working member of her team whose good nature was appreciated by his workmates. I interpolate, that she regarded the circumstances of his offending as being completely out of character for the person she and her colleagues had known and worked with.
There is a history of mental illness in the family with a number of relatives being afflicted by the dreadful disease of schizophrenia including the offender’s middle brother Thomas. Thomas took his own life due to his affliction. As with the other members of his family, the offender took his brother's death very hard. Fortunately, in Dr Nielssen's opinion the offender has escaped that disease and given his age, the chance of its late onset is regarded by Dr Nielssen as remote.
Dr Nielssen did receive a history of symptoms consistent with undiagnosed and untreated depression over a period prior to his arrest. This may have been related to the breakdown of his only long-term relationship which occurred some years before he met Ms Slastion. I note that the offender had been single in the interim after his previous long-term relationship ended and before meeting Ms Slastion. With respect to his depression, the offender is now receiving treatment in custody. Dr Nielssen did not express the opinion that there was any connection between the offender’s offending and the diagnosis of depression nor did he express the view that the offender’s time in custody would be more onerous by reason of it. The good progress he has made in custody to my mind suggests otherwise.
I am satisfied that the offender is remorseful for the most serious offence for which he is responsible. I am satisfied that the conditions of s 21A(3)(i) of the Sentencing Procedure Act have been complied with.
The offender has provided evidence that he has accepted responsibility for his actions, not only through his plea of guilty, as is important, but by what he has said to others, as I have recounted in my summary of the references tendered on his behalf. I accept those matters as honest and sincere accounts by the authors of their experience of the offender and their understanding of his attitude to his offending.
Moreover, a letter has been tendered which the offender wrote in his own handwriting expressing what I find to be his remorse in his own words. While he did not give evidence before me, I accept the letter (Exhibit A.2) as sincere. The Crown have not submitted that I should find the offender is not remorseful.
I accept that by his letter the offender has acknowledged not only his responsibility for taking Ms Slastion’s life but also the injury he has caused to her family and friends. I do not propose to set out the letter in full, but it is clear from it that the offender acknowledges that he cannot undo the wrong he has done and his disentitlement to forgiveness from Ms Slastion’s family. However, he states, “I promise to live a life of redemption to better myself, live a clean life and to better the world for Anastasiia” (sic).
Given what the prison chaplains have said about him and his very good behaviour and productiveness in custody, I accept he is attempting to fulfil that promise.
The Crown argued that a conviction for murder demands the imposition of a lengthy sentence, and it is not possible for the Court to be confident about the offender’s prospects of rehabilitation and his related risk of reoffending. At best, I should find those prospects to be guarded.
With respect, I am not persuaded by this Crown submission. I have found the offender to be genuinely remorseful, and this is usually considered to be essential to rehabilitation and, generally speaking, a good prognosticator of it.
Moreover, I have found the offender to be of prior good character, not only on the basis of his previous good criminal record but also having regard to the testimonials I have received. Some of those testimonials have, of course, been from relatives, and accordingly one may think it prudent to be cautious about accepting those testimonials unreservedly. However, I have no reason to reject the evidence, and it is consistent with the evidence of the offender’s family friend and last employer, the independent prison chaplains and authors of the prison case notes.
In particular, I have been impressed by how well the offender has applied himself to his own rehabilitation so far as there is scope for it while remanded in custody. The accounts given in the prison case notes confirms that, over the last two years and nine months, he has taken every advantage of the opportunities made available to him to engage in rehabilitation programs, self-improvement courses and productive work in prison enterprises. Nor should his applying himself to the observance of his religious faith be discounted. I find his conduct in custody has been exemplary, no easy thing to achieve.
I fully appreciate that there will yet be long years ahead of him in custody. His resolve to reform is likely to be tested by this. However, the personal attributes that made others think well of him in the community prior to this offending stands him in good stead for the trials ahead.
I am satisfied that the offender’s prospects of rehabilitation are good and he is unlikely to offend again. So far as reoffending is concerned, I should acknowledge that Dr Nilessen thought his prospects rather depended upon the offender getting on top of his substance abuse issues. Given the significance of self-induced intoxication to this most serious offending, doubtless that is correct, but as I have already indicated, he seems to be addressing that matter in custody and has expressed his intention to remain sober.
The maximum penalty for murder is imprisonment for life (s 19A Crimes Act 1900 (NSW)). Nevertheless, I am empowered to impose a sentence of imprisonment for a lesser term (s 21 Sentencing Procedure Act) unless the offender’s level of moral culpability in the commission of the offence is so extreme that the community interest in retribution, punishment, community protection and deterrence can only be met through the imposition of a life sentence pursuant to s 61 of the Sentencing Procedure Act. This case does not fall into that extreme category, nor have the prosecution sought to argue the contrary.
As I have already remarked, murder is an offence attracting a standard non-parole period and the period applicable to this case is 20 years. I also note that the murder of Ms Slastion predates the commencement of the recent amending legislation increasing the standard non-parole period where the victim is an intimate partner to 25 years (Table of standard non-parole periods, Sentencing Procedure Act). The maximum penalty and the standard non-parole period are important guidelines to be borne in mind when fixing the appropriate sentence for this offence and this offender (Muldrock [27]).
It is essential that I must have regard to the purposes of sentencing (s 3A Sentencing Procedure Act), those most relevant for this case include retribution in the sense of adequate punishment for the offence, accountability of the offender, denunciation of his conduct and recognition of the greatest harm that can be done to Ms Slastion as the victim of the crime.
In cases of a domestic violence murder, it is well to bear in mind what was said by the High Court of Australia in Munda v Western Australia (2013) 249 CLR 600 at [55]:
“A consideration with a very powerful claim on the sentencing discretion in this case is the need to recognise that [the offender], by his violent conduct, took a human life, and indeed, the life of his [intimate domestic partner]. A just sentence must record due recognition to the human dignity of the victim of domestic violence and the legitimate interests of the general community in the denunciation and punishment of a brutal, alcohol-fuelled destruction of a woman by her partner. A failure on the part of the state to meet out a just punishment of violent offending may be seen as a failure by the state to vindicate the human dignity of the victim; and to impose a lesser punishment by reason of the identity of the victim is to create a group of second-class citizens, a state of affairs entirely at odds with the fundamental idea of equality before the law.”
I have already acknowledged that the offender, unlike some other offenders who come before the court for sentence for the murder of their domestic partners, is not a habitual or a serial domestic offender. This is not a case of escalating domestic abuse over many years culminating in the murder of his female partner. However, he did take the life of Ms Slastion for whom he professes great love in what can only be described as an alcohol-fuelled and frenzied attack, albeit not one in which extreme or severe violence was used. Nevertheless, denunciation of his conduct and vindication of the dignity of Ms Slastion’s life demand a just punishment. It is for this reason that there is limited scope for leniency notwithstanding the strength of the offender’s subjective case as I have explained it to be. Although rehabilitation is a purpose of the law of sentencing and the offenders exemplary conduct in custody calls that purpose into focus.
General and specific deterrence remain important factors; specific deterrence less so because of the offender’s good prospects of rehabilitation. But these matters must be reflected in the sentence.
The sentence I impose will consist of a non-parole period and an additional term. The non-parole period is the minimum period which justice demands the offender remain in custody on account of his offending. The additional term makes up the maximum period the offender will serve before his release. No one, least of all the offender, should assume that release upon the expiration of the non-parole period is a foregone conclusion. That will be a matter for the State Parole Authority in due course. While it is not for me to say, the offender’s best prospect of being released when first eligible will depend upon him continuing his exemplary conduct in custody over the whole of the non-parole period.
Mr Stratton asked that I find special circumstances for the purpose of varying the statutory ratio between the non-parole period and the additional term. This would permit me to impose a shorter non-parole period in the special circumstances of the case. The basis of the application was a longer time under supervision in the community which would further promote the offender’s rehabilitation. It is not very common to make a finding of special circumstances when sentencing offenders for the crime of murder. This is because the statutory ratio itself generally provides for a fairly lengthy time in the community, extending beyond the period during which supervision is generally available, namely a period of three years. I am not persuaded that I should find special circumstances.
As I have indicated, I propose to factor such leniency as I regard as appropriate into the sentence I propose to pass. But it will allow sufficient time for necessary supervision to re-integrate the offender into the community, assuming he does all he can to promote his candidacy for release on parole when first eligible.
But for the early appropriate plea of guilty, the sentence I would have passed on the offender for the murder of Ms Slastion would have been one of 24 years. Allowing the discount of 25% to which the offender is entitled under statute for his plea of guilty, that sentence will be reduced to one of 18 years. I have decided not to vary the statutory ratio between the non-parole period and the additional term. I will fix the non-parole period at 75% of the head sentence of 18 years, being a period of 13 years and 6 months. I backdate the commencement of the sentence to 25 February 2023 when the offender was first arrested for the offence. He has remained in custody solely for this offence ever since.
Isaac Costa, on your plea of guilty, I convict you of the murder of Anastasiia Slastion. My orders on sentence are as follows:
I sentence you to a term of imprisonment of 18 years, having the following components:
(a) a non-parole period of 13 years and 6 months commencing on 25 February 2023 and expiring on 24 August 2036, and (b) an additional term of 4 years and 6 months commencing after the expiration of the non-parole period and expiring on the 24 February 2041. You will be first eligible for parole after the expiration of the non-parole period on 24 August 2036.
**********
R
Costa [2025] NSWSC 1575
(1989) 167 CLR 348
(2011) 244 CLR 120
(2013) 249 CLR 600
(2006) 66 NSWLR 566
It is evident from the agreed facts and from the accounts of the offender’s parents, Lindsey and Clement Costa, contained in their affidavits both sworn on 8 December 2025, that the offender formed a very firm attachment to Ms Slastion almost immediately. It is also evident that he was very possessive of and emotionally dependent upon her, and on another description, “needy”.
It is also evident that the relationship between the offender and Ms Slastion was characterised by bouts of heavy drinking in each other's company. I am satisfied from the agreed facts, the statements of lay witnesses (Exhibits C, D, and F) and the expert evidence of Dr van Nieuwenhuijzen, a pharmacologist and toxicologist, that heavy drinking exacerbated the offender’s possessiveness and introduced volatility to the relationship. I accept that when intoxicated the offender expressed his jealousy in a denigrating manner which he would promptly regret when sober.
Without in any way casting any responsibility whatsoever for what happened on Ms Slastion, it was also apparent that she was no ‘shrinking violet’ when intoxicated. She could express herself forcibly and the offender complained that, during disagreements, she would strike him.
Having highlighted what must be taken to be the negative aspects of the relationship, I am not in any doubt that the offender’s feelings for Ms Slastion were genuine and sincere. Having been in the relationship for only a few weeks, he bought her an expensive bracelet for Valentine's Day which Ms Slastion happily wore and even showed off to others.
It seems that Ms Slastion was between jobs for at least part of the time they were together and for that reason was spending time, at least intermittently, at the offender's residence in Greystanes. In each other’s company, they continued to drink heavily. The offender was working full-time and commuting to and from work. He complained to Dr Nielssen of the effects of alcohol and limited sleep upon him.
There is some contradiction in the evidence about the movements of Ms Slastion and the offender during the afternoon and early evening of 24 February 2023. The more extensive account of their movements recorded by Dr Nielssen seems inconsistent with the agreed facts, and I will be guided by the latter.
The offender had worked at North Sydney on Friday 24 February 2023 and Ms Slastion had remained at his residence. On the way home from work the offender stopped at a bottle shop and spent $241.73 on the purchase of what appeared to be a large quantity of alcohol, including spirits, premixed drinks, beer, wine and fruit juice. I infer that after he arrived home at least some of that liquor was consumed as he and Ms Slastion got ready to go out for the night. They left at about 6pm to attend the Greystanes Inn where a band was playing.
During the course of the evening, they ran into an acquaintance, a Ms Cynthia Griffin, and they sat together for a couple of hours. Ms Slastion became locked in conversation with Ms Griffin and made complaints to the latter about the offender’s “neediness”. During this period Ms Griffin noticed that the offender’s attitude changed. He appeared to become upset when his attempts to insert himself into the conversation were rebuffed by Ms Slastion.
Ms Griffin and Ms Slastion decided to dance. After a short time, the offender joined them on the dance floor and sought to “cut in” a number of times. When the offender was again rebuffed, this led to the exchange of sharp words between Ms Griffin and the offender after they left the dance floor. She formed the opinion that that the offender was unhappy. While he was affected by alcohol he did not appear “overly drunk” to her.
I interpolate that it was Dr van Nieuwenhuijzen’s opinion formed by extrapolation from the results of blood tests taken the following morning, a process in which pharmacologists are expert, that at midnight Mr Costa’s blood-alcohol level would have been in the range of 0.130g/100ml and 0.302g/100ml. In her opinion, it “most likely” would have been 0.195g/100ml (Exhibit B, [19]). With respect, this is obviously a much more reliable guide to the offender’s level of intoxication than the lay opinion of Ms Griffin who had also been drinking at the hotel for some hours. A reading of 0.195g/100ml would be well over the limit for the High Range Prescribed Concentration of Alcohol (PCA) offence and suggests a person who is very drunk, however habituated he or she might be to the effects of alcohol.
Shortly before 11:30pm, the offender and Ms Slastion were picked up from the hotel by an Uber driver. The driver noticed that they appeared intoxicated with slurred speech, and smelling strongly of alcohol. In the Uber, Ms Slastion was complaining volubly about the offender’s conduct at the hotel. The Uber driver said the offender was calm and did not raise his voice. Ms Slastion spoke over the top of him, swearing at him and proclaimed, "things aren't working well between us. I'm going to break up with you”. She expressed the intention to end the relationship more than once during the short ride home.
When they arrived home, the offender must have had some difficulty with his key because Ms Slastion was yelling at him, using profanity, to open the door. He asked her to “keep it down”, and soon enough they gained entry to the offender’s residence.
Notwithstanding his plea of guilty, the offender has not given a full and detailed account of what happened after entry was gained to the granny flat. He told Dr Nielssen that he did not remember every moment of that evening and claimed to have “blacked out” around the incident. I fully accept that the offender was very drunk, but Dr Nielssen does not give a medical reason for why that should have happened.
Dr van Nieuwenhuijzen opines that the effects of alcohol are dose dependent. Repeated use leads to tolerance or habituation so that a chronic user is less affected by the same dose than an occasional drinker. She said that at blood-alcohol levels of 0.100g/100ml and above, the effects include impaired judgment, and changes in mood or personality. The impulse disinhibition associated with alcohol consumption can lead to a loss of emotional control and increases the risk of violence. Severe assaults involving a loss of control may occur. It may heighten a person's mood. If a person is upset or angry alcohol can cause more negative behaviours such as aggression or violence. While she mentioned "impaired cognitive function” as an effect of a high dose of alcohol consumption she did not specifically refer to the absence of memory as an effect. Those with experience of life may be familiar with people claiming a loss of recall when they are concerned about how they may have behaved while under the disinhibiting effects of a high dose of alcohol.
As I have said, there is no account from the offender of what happened inside the granny flat and why. Only he and Ms Slastion were present. It is not known what words might have been exchanged between them including whether Ms Slastion continued to proclaim that she proposed to end the relationship, which the offender would have found very hurtful. But I will not speculate.
It is an agreed fact that after the offender had killed Ms Slastion, his friend, Mr Walker, called after completing shift work in response to earlier messages from the offender. The offender said, amongst other things, “you have been a good friend. It’s too late… you have been a good friend”. Mr Walker was concerned by the offender’s tone and drove to his place. When he arrived, the offender was absent and not answering his mobile phone. The door to the granny flat was open and Mr Walker observed Ms Slastion’s body lying limp on the bed. He called triple zero.
The offender had left the granny flat and gone into his parent’s residence. He woke his father and said, “[Anastasiia] started hitting me again and I lost it and I hit her back…I’ve been trying to resuscitate her, but I can’t. I didn’t mean to hit her, I just lost it and snapped”. His mother said the offender was crying, and she noticed blood on his right shoulder and forehead. He said to her, “I killed Anastasiia. I’ve bashed her to death…I tried to resuscitate her for half an hour before I came up here”. I accept those accounts given to his parents in the immediate aftermath of him killing Ms Slastion are reliable accounts of what happened in general terms. Other evidence establishes that the bashing was extensive. I have expressed myself carefully having regard to the expert evidence I will review a little later.
The offender’s granny flat, as would be expected, is a modest dwelling. From Professor Johan Duflou’s summary in his report of the findings of the crime scene examiners (Exhibit 1.10, par [14]), it is evident that the bashing of Ms Slastion by the offender was a dynamic event involving them moving around the granny flat. Professor Duflou said (at par [14]):
On the other hand, I accept the evidence of Professor Duflou that the physical consequences of the offender's actions as documented by Dr Irvine at the post-mortem do not bespeak severe or extreme violence. Rather, the violence or force inflicted was in the moderate range. And, it is relevant to consider that there is no obvious direct cause of death on the whole of the expert evidence.
Often in cases of murder by an intimate partner. The evidence discloses a long history of escalating violence perpetrated by the male against the female over a period of months or years. There is no evidence of that type here. Indeed, while there was emotional volatility in the relationship and the offender seems to have been possessive and needy, there is absolutely no suggestion in the evidence of any previous violence perpetrated by him against her.
I accept in the context of his own self-induced intoxication and his resentment about being rebuffed at the hotel the offender had a ‘brain snap’ during the continuing argument with Ms Slastion.
Given his plea of guilty, it must be accepted that he actually turned his mind to achievement of the purpose of at least inflicting serious bodily harm upon her. And the length of the assault which continued throughout the granny flat, and the number of blows struck, probably involving a degree of strangulation, amply support that conclusion.
Given the somewhat unusual confluence of circumstances leading to Ms Slastion’s death, as I have described already, I am not satisfied beyond reasonable doubt that the offender intended to kill her. He used only his bare hands; no weapon was used. I accept the force he applied to Ms Slastion’s head was moderate rather than severe or extreme. Although the assault must have continued for some time, his regret of his actions in the immediate aftermath is more consistent in my mind with his response to an unexpected and unintended outcome, rather than regret at having achieved the purpose he intended. I am not suggesting in any way that the death of Ms Slastion was an accident.
I find that the offender intended to really seriously injure her, but I am not satisfied to the requisite standard that he intended to kill.
The fatal assault on Ms Slastion by the offender was a sudden eruption even if Ms Griffin had earlier formed the opinion that the offender was upset or angry. She had no inkling of violence on the part of the offender with respect to Ms Slastion, so far as that may be relevant.
The offender assaulted Ms Slastion with his bare hands, no weapon was used. While the attack was sustained and involved the infliction of multiple injuries, the violence perpetuated was moderate rather than severe or extreme. There was probably a degree of strangulation or asphyxiation by other means. Other factors for which the offender was not responsible contributed to Ms Slastion’s death.
While avoiding the compilation of a grizzly table of human catastrophe arising from the Court’s experience of the many forms which the offence of murder can take, I am of the view that the objective gravity of this case is somewhat below the middle range of seriousness.
Dr Nielssen rather latched on to the diagnosis he made of a substance use disorder involving what he regarded as quite hazardous quantities of alcohol consumption during the offender’s relationship with Ms Slastion and a longitudinal history of cannabis use since the age of 13 and abuse of cocaine in the year preceding the offence. Dr Nielssen considered there was a nexus between the offender’s mental state and the offence in the disinhibiting effect of a very large amount of alcohol in a person who is sleep deprived. I interpolate however, neither at common law nor under s 21A(5AA) of the Sentencing Procedure Act is it permissible to treat self-induced intoxication of the offender at the time the offence was committed as a mitigating factor on sentence. Doubtless it may explain why the offence was committed.
I have received a number of references about the offender’s character. His half-sister, Rebecca described the offender as a person of good character who conducts himself with honesty, integrity and respect for others. She described him as the ‘peacemaker’ in the family. She had never seen him show any signs of aggression, violence or intimidation towards anyone. She described him as a hard-working man who takes pride in earning an honest living.
I have referred to his employer’s reference already which speaks of the offender in very positive terms.
A family friend who also worked as the office manager for the same electrical company which employed the offender as a truck driver and excavator operator, also spoke highly of him. She said he was found to be very honest, punctual and hard-working. He was well-liked and respected by the staff. She described him as always gentle with a kind manner about him. She regarded his offence as out of character, and from speaking with him, believes him to be remorseful; a matter I will return to. She speaks highly of the family generally.
Since his arrest and during his time in custody, the offender has reconnected with his Catholic faith and I have received two references from prison chaplains confirming this and his regular attendance at religious services. Both spoke highly of the offender and confirm his prison employment and his keenness to undertake such courses as have been made available to him while on remand. This included employment courses, courses relevant to his religious faith and rehabilitation courses.
The offender has undertaken a domestic violence course which he completed in six sessions over the period of one month. From my review of the prison case notes it is evident that he has been very well behaved in custody, respectful to officers, and his attitude is appreciated by them. He has worked in various occupations in trusted areas. He has progressed to the position of leading hand in some of the occupations through which he has been rotated. He has happily shared his skills with other inmates who may be novices in the workplace.
He has been trusted to perform work in the café at his current placement to which members of the public are admitted. The case notes also confirm his regular attendance at church services. To address his substance abuse issues, he has undertaken the EQUIP course and has been registered for the buprenorphine course which Dr Nielssen says is appropriate to suppress cravings for intoxicating substances.
He has undertaken educational study units and hopes to be able to undertake tertiary studies from custody.
A reference from his surviving elder brother, Guiseppe, also testifies to him being a hard-working and reliable person. His responsibility for the murder of Ms Slastion has come as a shock and is regarded by his brother as completely out of character. He testifies to the offender’s remorse. He confirms that the offender has always been known as a gentle and loving person.
I reiterate that it is accepted by the prosecution that the offender pleaded guilty to the charge of murdering Ms Slastion at the first available opportunity. I regard his plea as an expression of a willingness to accept responsibility for his crime which is commendable notwithstanding the obvious strength of the Crown case. The prosecution accepts, and I agree, that he is entitled under statute to a 25% reduction in the sentence which would otherwise have been passed for the utilitarian value of his plea.
I am also obliged to advise the offender that his offence is a serious offence for the purpose of the Crimes (High Risk Offenders) Act 2006 (NSW) which means that the Attorney General has the power to make an application to the Supreme Court for his continued detention, or supervision in the community after the expiration of the sentence which I will pass. Again, whether such an application will be made is not a matter for me, but it may depend upon whether the offender, as I have said, continues along his present path of exemplary conduct in custody for the whole term of his sentence.