R (O’Brien) v HM Assistant Coroner for Sefton, Knowsley and St Helens [2026] EWCA Civ 499 (22 April 2026) here.
The Court of Appeal has handed down some useful guidance on how to approach the thorny issue of causation in deaths where domestic violence has been a factor and there had been previous contact with police. At first instance the High Court had held that it would have been speculative of the Coroner to consider what might have been the position had the perpetrator been arrested before the death: the Court of Appeal did not agree.
In this 17 page judgement Lord Justice Edis guides us all on how to navigate the various “what ifs” associated with the potentially uncertain terrain of the criminal justice process. Readers may well now be rushing to the latest editions of various criminal sentencing guidelines to navigate this new terrain.
Background
Regular readers of this blog may remember the sad case of Linda O’Brien (see blog post here) and the decision of HHJ Sephton KC in the Divisional Court that was the subject of this appeal. Ms O’Brien died on 9 May 2020 having fallen to her death from the window of her flat at 0243am. Mr McMahon, which whom she had been in an intimate relationship, was at her flat and called emergency services at 03:03. The post mortem showed that most of Ms O’Brien’s injuries were caused as a result of the fall, but the pathologist raised concerns about some of the injuries to the right side of her face which were consistent with being punched or slapped, and in addition, there was evidence that she was struck with a weapon in the left shoulder/arm area and lower right shin/foot. A broken mop was found at the scene.
There had been a history of abuse. McMahon had been the subject of a restraining order preventing him from contacting Ms O’Brien for 18 months in 2017 and again for a period of 5 years following his conviction for ABH in 2019. On 7 April 2020, an anonymous call was made to police to report an ongoing domestic incident where screaming was heard. Four police officers attended and found Ms O’Brien and McMahon together, apparently intoxicated. Ms O’Brien was described as calm, said nothing had happened and could not understand why the police had been called. None of the police who attended were aware that Mr McMahon was the subject of a restraining order – the Police National Computer (‘PNC’), NICHE and STORM logs did not contain any mention of the order. Officers stated subsequently that had they been aware of the restraining order, they would have arrested McMahon. A Vulnerable Person Referral Form was completed but did not record the restraining order, and the incident was not referred to the Multi-Agency Risk Assessment Conference (MARAC) or the local Independent Domestic Violence Advocate. Police officers discovered the error on the 15th April and steps were taken to obtain witness evidence from officers for the purpose of prosecuting McMahon for breach.
Causation
The Court of Appeal set out the oft-cited case of Tainton[1] and the well-known remarks by Sir Brian Leveson PQBD:
“Third, it is common ground that the threshold for causation of death is not the same thing as the standard of proof required to prove causation of death. In cases such as this, the latter is proof on the balance of probabilities. It is agreed that the threshold that must be reached for causation of death to be established, is that the event or conduct said to have caused the death must have ‘more than minimally, negligibly or trivially contributed to the death’ (see e.g. R (Dawson) v HM Coroner for East Riding and Kingston upon Hull Coroners District [2001] EWHC Admin 352; [2001] Inquest LE 233 per Jackson J at paras 65-67). Putting these concepts together, the question is whether, on the balance of probabilities, the conduct in question more than minimally, negligibly or trivially contributed to death”. [§41]
“The conduct or event must make an actual and material contribution to the death of the deceased. As Ms Dolan pointed out, it is not enough, in the present context, to show that a particular event, or particular conduct, deprived the deceased of an increased chance of life or, to put the point the other way round, made his death more probable than it would otherwise have been”
Translating these principles onto the facts in this case, the Court of Appeal in O’Brien framed the issue of causation thus:
“…the question for the jury to decide, if the causation issue were left to them, would be whether an arrest of Alan McMahon on 7 April 2020 would, on the balance of probabilities, have prevented the death of Ms O’Brien O’Brien on 9 May 2020” [§24]
The Assistant Coroner decided that the matter should not be heard with a jury and that Art 2 ECHR was not engaged. In pre-action correspondence, he stated that it could not be known that had Mr Mahon been arrested, it would have resulted in his incarceration before or on the date of Ms O’Brien’s death or that it would have prevented his re-attendance at the address on the date of Ms O’Brien’s death, or indeed whether his presence was the case of death. The Court of Appeal described the Coroner’s reasoning as difficult to follow given that McMahon had been given IP status. There was a clear evidential basis for investigating whether his presence at the flat was a cause of death:
The evidence suggests that Linda O’Brien sustained injuries which were not explained by her fall, and which were fresh; she fell when she was using the route by which she had planned to escape from him; he had a propensity to use violence against her when he was drunk; she is very likely to have been in fear of him and this explains why she tried to get away. Obviously, if his presence in the flat is not found to have been a causative factor in her death, then the steps available to the police to prevent him from being there will not be found to have contributed to it. However, the coroner was clearly wrong, in his letter written after the event, to express a concluded view on this question as a reason for not investigating the role of the police [§29]
The Court of Appeal agreed with the Coroner that:
“…an arrest followed by release on bail with whatever conditions would probably not have kept [McMahon] away from Linda O’Brien’s flat. The restraining order had failed to achieve this, and there is no reason why bail conditions would have been any more successful. This is why he would probably have been remanded in custody had he been arrested on 7th April” [§30].
The Court of Appeal did not agree however that it was right for the Coroner to decide, at the preliminary stages of the Inquest, that it would not be known whether his arrest would have led to McMahon being in prison. Taking such a stance without looking at his antecedent history was premature, and irrational.
The Court of Appeal considered that the decision-making should have included consideration of the Sentencing Guidelines and consideration of the outcome of the arrest [§31]. Given McMahon’s previous sentence of 22 weeks’ imprisonment for the assault against Ms O’Brien in August 2019, it is likely that the outcome for him on a guilty plea for breach would have been no better and possibly worse. It would have been aggravated by the fact that his total term of imprisonment (of which he would have likely served half) would have expired in January 2020, just a few weeks before 7th April. The breach of the restraining order may have been a more serious offence than the assault. A study of his antecedents (the details of which the police would have readily to hand) would assist in determining the range of outcomes and it was premature to reach a conclusion about the likely outcome of events had he been arrested on 7 April 2020 without conducting that investigation [§34]. After assessing the Sentencing Guidelines for breach of a restraining order that were in effect from October 2018, the Court of Appeal found that it would likely have been considered as Culpability B and Harm Cat 2 which carried with it a starting point of 12 weeks’ imprisonment with a range extending up to one year. The offending would have been aggravated by McMahon’s previous convictions having regard to the nature of the offence and the relevance to the current offence as well as the time that had elapsed since that conviction, as well as the breach being committed shortly after the order was made and a history of disobedience to court orders [§38]. The sentence would unlikely have been suspended. It is therefore likely that had McMahon been sentenced before May 2020, he would have been in prison on that date [§39].
Speculation or reasonable inference?
The above analysis assumes that McMahon would have been charged and prosecuted had he been arrested. HHJ Sephton KC said that it would not be known whether the breach would have been prosecuted but there was no explanation as to why the CPS would have not applied the Code for Crown Prosecutors as it was obliged to do. Furthermore saying that he did not know whether a prosecution would have followed was an example of an error in approach: the judge was required to consider whether the Coroner’s decision was lawful rather than take his own decision on the factual issues. The Coroner did not express any doubt about the likelihood of arrest and prosecution following the events of 7 April 2020 [§42].
The next question that the Court of Appeal considered was what would have happened had McMahon pleaded not guilty. Would he have been granted bail? The Coroner appears not to have considered this question but the Divisional Court placed some reliance on this issue stating that bail would likely have been granted. Again, the Court of Appeal disagreed: there were substantial grounds for believing that McMahon would have committed further offences whilst on bail, indeed the Coroner had relied on McMahon’s disobedience to previous orders in his pre-action correspondence. This was not an irrational view, and had the magistrates reached the same conclusion, bail would likely have been refused. The Divisional Court fell into error in relying on the grant of police bail during the investigation into the allegation of murder –McMahon had never been charged with that offence and the police had no power to do anything other than grant him bail or release him unconditionally once it was no longer necessary or possible to detain him under PACE. Again, the Divisional Court in making this decision was not reviewing the decision of the Coroner but substituting his own view [§43].
The criminal justice process is not random
The Court of Appeal criticised the approach of the Coroner and the Divisional Court for treating the criminal justice process as though “it were a random affair whose outcomes could not be predicted”. Whilst it is true that other decisions could have been taken, that possibility does not prevent an assessment of:
“…what would probably have happened. That assessment should proceed on the basis that the decision-makers, the police, the Crown Prosecution Service and the court, would have acted rationally on the evidence available and would have been aware of the domestic abuse context in which the offence had been allegedly committed…[t]o find that the decision-makers would have applied these principles rationally and have made decisions in such a way that Alan McMahon was in custody on 9 May 202 is, not, as the judge thought, to reach a conclusion which is “entirely speculative”. There is no indication that coroner had the Sentencing Guidelines and the Code for Crown Prosecutors I have mentioned in mind, or knew anything about sentencing practice and the making of charging or bail decisions. Many courts will have the necessary expertise to reach sound conclusions without the benefit of any evidence on these questions, but If a court considers that it does not, then expert evidence is admissible and available.” [§44-5].
Had the Coroner obtained McMahon’s antecedents, it would have rapidly become clear that he would not have been granted bail and that he would have received a substantial custodial sentence on conviction. The conclusions reached by both the coroner and the judge in the absence of antecedents were flawed on that ground alone [§46].
Footnotes
[1] R (Tainton) v HM Coroner [2016] EWHC 1396 (Admin)