The Supreme Court hands down judgment in Lewis-Ranwell (Respondent) v G4S Health Services (UK) Ltd and Devon Partnership NHS Trust and Devon County Council (Appellants) [2026] UKSC 2

On 21 January 2026, the Supreme Court handed down judgment in Lewis-Ranwell (Respondent) v G4S Health Services (UK) Ltd and Devon Partnership NHS Trust and Devon County Council (Appellants) [2026] UKSC 2.

On 10 February 2019, the claimant, Mr Lewis-Ranwell, killed three elderly men during a serious psychotic episode. He was later charged with their murders, but was found not guilty by reason of insanity. He was detained at Broadmoor Hospital, where he remains. In early 2020 he brought civil proceedings against the defendants: G4S Health Services, which provided forensic medical services to persons in custody on behalf of the local police; the Chief Constable of Devon and Cornwall Police; Devon Partnership NHS Trust, a mental health trust which was responsible for liaison and diversion services to those who were in police custody and needed them; and Devon County Council, the local authority responsible for approved mental health professionals who were responsible for Mental Health Act assessments in the area. The claimant sought compensation for the consequences of the three killings, and an indemnity against any claims brought against him by the families of those he had killed. The issue in the appeal before the Supreme Court was whether the doctrine of illegality barred the civil claim. 

In the days just before the killings, the claimant was arrested and detained by police on two occasions for a suspected burglary and an assault. While detained, he behaved violently and appeared mentally very unwell. He was seen by mental health practitioners. The need for mental health assessments was discussed, but they were not arranged before he was released on bail on the day of the killings.

The claimant alleged that the four defendants negligently failed to provide him with a mental health assessment and adequate mental health care. He claimed that, but for the alleged negligence, he would have been hospitalised and would not have killed the three men. Instead, he was released into the community while suffering psychosis. He sought damages for his compulsory detention and its consequences, and an indemnity against any claims brought against him by the relatives of the men he killed.

The defendants (except Devon and Cornwall Police) applied to strike out the claim, relying on the doctrine of illegality: they argued that because the claimant’s actions in killing the men were illegal, he could not rely on them in bringing a negligence claim. The application was dismissed at first instance, and was appealed to the Court of Appeal, where it was dismissed. The three defendants then appealed to the Supreme Court.

The Supreme Court unanimously allowed the appeal, and held that the claimant was barred by the doctrine of illegality from bringing civil proceedings in negligence to recover compensation for the consequences of the killings.

While the claimant had not been convicted of a criminal act (due to his insanity), the Supreme Court found that the illegality defence was nonetheless engaged, because the claimant had killed the three men without lawful justification and as such had breached a fundamental moral rule of our society: you shall not kill. A criminal conviction was not necessary to pass the threshold of engaging the illegality doctrine.

The Supreme Court then turned to consider whether the defence should apply in the present case, applying the trio of considerations set out in Patel v Mirza [2016] UKSC 42; [2017] AC 467 [135]. These are: a) the underlying purpose of the prohibition which has been transgressed and whether that purpose is furthered by denial of the civil claim, b) any other relevant public policy on which denial of the claim will have an impact, and c) whether denial of the claim would be a proportionate response to the illegality.

The Supreme Court held that the purpose of the prohibition is the preservation of life and the deterrence of unlawful killing. It applies with equal force to an individual found not guilty of murder by reason of insanity as it does to someone convicted of murder. The claimant’s conduct was in no way justified or excused, despite his acquittal on the grounds of insanity. The Supreme Court considered the potential deterrent effect of a clear rule that unlawful killing never pays, and that allowing the civil claim to proceed would give rise to a series of inconsistencies which would damage the integrity of, and public confidence in, the legal system. The trial judge in the criminal proceedings was required by the jury’s verdict to make a hospital order and restriction order to protect the public. It would be inconsistent for a civil court to order payment of compensation to the claimant for the consequences of lawful detention ordered by a criminal court.

The Supreme Court further held that while it is generally in the public interest that courts adjudicate civil wrongs, and allowing the civil claim would allow examination of what may have gone wrong prior to the killings, alternative procedures such as inquests and public inquiries exist which are better suited for that purpose. It therefore found that the policy considerations in favour of maintaining the integrity of the legal system greatly outweighed those in favour of permitting a claim.

As to whether denial of the claim would be a proportionate response to the illegality, the Supreme Court found that the killings were of the utmost seriousness and that they were central to all heads of loss claimed in the civil action. Therefore, denying the claim was proportionate to the illegality.

Judith Ayling KC, instructed by DAC Beachcroft LLP, acted for the third defendant/appellant, Devon Partnership NHS Trust, at first instance and before the Court of Appeal and Supreme Court. She led James Goudkamp of 7 King’s Bench Walk. In the Supreme Court Alex Ruck Keene KC (Hon) was also instructed on a point arising out of the UN Convention on the Rights of Persons with Disabilities.