The recent Supreme Court judgment in Alexander Lewis-Ranwell v G4S Health Services (UK) Ltd and others [2026] UKSC 2 represents a significant development in the law relating to mental health, legal responsibility and the duties of public sector bodies. In this article we examine the key issues addressed by the Supreme Court, including the scope and application of the doctrine of illegality and its implications for public bodies managing complex mentalhealthrelated risks. The facts of this case are, however, profoundly tragic and distressing, and we remain mindful of this in our commentary and analysis below.
DWF were instructed on behalf of Devon County Council.
Background
On 8 February 2019, the Claimant, having previously been diagnosed with schizophrenia and psychosis, was arrested on suspicion of burglary and was assessed by mental health staff from G4S, one of the four defendants to whom the police sub-contracted the performance of such duties. He was subsequently released.
Two days later on the morning of 10 February he attacked a farmer and was again detained by the police. Although he continued to exhibit erratic behaviour while in custody, the Claimant was again released on bail. Later that same day, he killed the three elderly men, two of whom were 84-year-old twin brothers, while acting under a delusional belief that they were paedophiles.
Devon County Council, the fourth defendant and third appellant, was responsible for the Emergency Duty Team, a community mental health team comprising approved mental health professionals (“AMHPs”) who provided and coordinated assessments and applications under the Mental Health Act 1983 (“the Mental Health Act”).
G4S, another defendant, was contracted by the Chief Constable (who did not participate in the appeal) to provide medical services to those in police custody.
Devon Partnership NHS Trust was responsible for assessing people with mental illnesses while in custody.
At his criminal trial, the Claimant was found not guilty by reason of insanity and was made the subject of a hospital order with restrictions under sections 37 and 41 of the Mental Health Act 1983.
The Claimant subsequently brought a civil claim for damages in negligence against the agencies/constabulary involved with him prior to the unlawful killings, together with a claim for damages for breach of Articles 3 and 8 of the ECHR, as incorporated into our domestic law by the Human Rights Act 1998.
The Claimant claimed (not an exhaustive list): -
- Damages for past and future psychiatric injury.
- Damages for past loss of liberty during his detention in police custody, prison and psychiatric hospital.
- Damages for his future detention in Broadmoor Hospital, and subsequent psychiatric units or supervised accommodation over a period of eight to nine years, pursuant to the terms of the section 37/41 order of the criminal court.
- Damages for loss of reputation due to adverse media coverage of the killings, arrest, charge, trial and detention.
- Past loss of earnings between 2019 and 2023 based on net profits from self-employment of £13,721 in 2018/2019.
- Future cost of a care package/treatment in 24-hour staffed accommodation after his release from psychiatric detention.
- Future psychological treatment in the community.
- Future legal costs relating to his detention, including representation at tribunal hearings.
- An indemnity against any claims brought against him, including claims by the families of men that he killed or any persons that he injured.
Three of the four defendants attempted to have the claim in negligence struck out, first before the High Court and then before the Court of Appeal, but were unsuccessful. The defendants argued that the defence of illegality operated as a complete bar to the claim in negligence. In other words, the Claimant's unlawful act of killing three men could not, as a matter of public policy, provide a platform for a claim for damages against third parties.
The Court of Appeal decision
The Court of Appeal observed that there was no binding authority on whether the illegality defence applied where a claimant was insane at the time of the unlawful acts. There is case law dealing with the situation where a claimant had been convicted of manslaughter by reason of diminished responsibility. In those cases, it is settled law that a claimant cannot recover damages because they were partially responsible for their actions. That was not the case where a defendant commits an unlawful act while insane and a verdict of not guilty by reason of insanity is in fact an acquittal. However, and of some significance, the underlying act remains unlawful.
The Court of Appeal – by a majority of 2:1 – held that where a person did not know that their unlawful act was wrong, they should not be prevented from pursuing a claim for damages against the agencies alleged to have failed in their care of such a claimant.
The Supreme Court decision
The Supreme Court ruled that claims for compensation in the tort of negligence by a Claimant who killed three people but was acquitted by a jury in the Crown Court on the grounds of insanity, are barred by the doctrine of illegality.
The Supreme Court first considered the threshold question. It recognised that it would be unjust if trivial acts of unlawfulness barred otherwise valid legal claims. It is not necessary for the actions of a Claimant to carry criminal responsibility to cross the threshold. The fact the Claimant was acquitted at his criminal trial had no bearing on the coherence of different branches of the law. This Claimant killed three men, in contravention of the sacrosanct principle "thou shall not kill". Notwithstanding the absence of criminal responsibility due to his insanity, the killings constituted unlawful conduct that engaged the illegality defence.
Having established that the threshold had been crossed, the Supreme Court then had to decide whether the defence should apply on the facts. This required the Court to consider the trio of considerations set out in the earlier Supreme Court decision in Patel v Mirza [2016] UKSC 42, namely whether denying the claim would further the purpose of the legal prohibition breached; the impact on any other relevant public policies, and whether denying the claim would be a proportionate response to the illegality:
a.) The purpose of the prohibition
The law seeks to protect the public and deter unlawful killing. Allowing the civil claim to proceed would give rise to inconsistencies which would damage the integrity of the legal system. The Claimant had been lawfully detained pursuant to the order of the criminal court.
b.) Other relevant public policies
The need to maintain the integrity of the legal system far outweighed the policy considerations in favour of permitting a claim. It would be inconsistent with the fact that tort law does not recognise insanity as a defence to liability. The victims of the killings could not sue the defendant authorities in tort, and it would bring the law into disrepute if the Claimant could.
c.) Proportionality of denying a civil claim
The Claimant’s conduct was of the utmost seriousness, central to the claims and whether he was aware of the nature and of his acts or not, those acts amounted to unlawful killing.
The three defendants applied to strike-out the claim in negligence but not the claims advanced under the HRA 1998 for the alleged contravention of Articles 3 and 8. The Court noted: -
"22...The defendants did not argue that the doctrine of illegality barred the claim under the Human Rights Act 1998 (“HRA”), the courts below being bound by the decision in Al Hassan-Daniel v Revenue and Customs Comrs [2010] EWCA Civ 1443; [2011] QB 866."
This means that the claims under the HRA 1998 can still proceed in theory, as it is only the claim in negligence that has been struck out.
Significance and wider application of judgment: Illegality and e-scooter claims
DWF are currently dealing with a number of similar claims where individuals who have attacked others, and were subsequently found not guilty by reason of insanity, are now pursuing damages against agencies involved in their mental health assessment/care. Those claims, in so far as they are advanced in negligence, cannot proceed further. However, the judgment is likely to have wider application beyond this category of case.
More broadly, the Supreme Court’s decision places renewed focus on the defence of illegality, which although sometimes considered by defendants, is often not pursued because its prospects of success can be difficult to gauge and predict. Importantly, the defence is not confined to cases involving extreme or shocking acts of violence. Following the Justices' thorough review through the relevant authorities, defendants in the private and public sectors may now be more inclined to explore its applicability in a broader range of civil claims. Motor insurers, for example, frequently seek to deploy the defence where an injured claimant was a pillion passenger on a stolen motorbike, although it very often fails on those facts.
The Supreme Court also made clear that a claimant’s conduct does not need to amount to a criminal offence to engage the illegality defence, yet equally, trivial unlawful acts will not cross the threshold. There has been much discussion of late on the subject of whether riding privately owned e-scooters unlawfully on the public highway, as distinct from e-scooters hired as part of an approved scheme, might engage the illegality defence if the rider was injured due to the highway authority’s failure to maintain the public road and the injured Claimant sought damages. While this would be an example of an unlawful act, albeit at a much lower end of the scale compared to the killing of three men, we anticipate that clients may now be more willing to consider the defence in such scenarios, particularly in light of the Supreme Court’s helpful review of the authorities in this area. The judgment has set out a template to follow when considering whether the defence is firstly engaged and secondly, can it be applied on the facts.
Interestingly, only a handful of reported decisions have so far explored civil claims arising from private escooter accidents, and even fewer have grappled with the potential application of the illegality defence. In O’Brien v Ringway Hounslow Highways [2024], the judge accepted that the Claimant’s unlawful use of a private escooter - riding on the pavement without a licence or insurance - was sufficient to justify consideration of the illegality defence and described unlawful escooter use as “a menace” and “the scourge of the high street”, noting strong publicpolicy reasons that could justify denying such claims. By contrast, in Dormer v Wilson [2025] - which did not involve an e-scooter, rather, the Claimant was a pillion passenger who was seriously injured on a stolen motorbike - the court stressed the limits of the doctrine, emphasising that a claimant must be aware of their own unlawful conduct before the defence can succeed, and cautioning against its application in cases involving strictliability offences.
Finally, the judgment is a high-level reminder – despite the circuitous route taken in this case - of the effectiveness of a strike-out application where a statement of case discloses no reasonable grounds for bringing a claim. This option should always be considered at the start of any claim, whether relying on an illegality defence or some other basis to seek a strike-out, as the costs savings of avoiding a trial can be significant and, if the entire proceedings are struck out, this is an exception to Qualified One-Way-Costs Shifting. In such instances, the defendant does not require permission of the court to enforce a costs order against the Claimant, which could have significant cost implications for both parties.
If you have any further questions about this case and its wider implications, please do not hesitate to contact Simon Johnson.
