In this article we look at the Supreme Court's decision in Lewis-Ranwell v. G4S Health Services (UK) Ltd and others [2026] UKSC 2 (judgment handed down on 21 January 2026), in which DAC Beachcroft acted on behalf of the successful second appellant, Devon Partnership NHS Trust.
In their landmark judgment, the Supreme Court unanimously held that the illegality defence is available (in principle and subject to the facts of the particular case) to defendants in negligence cases, even where the claimant has been found not guilty of a criminal offence (in this case murder) by reason of insanity.
Following DAC Beachcroft's previous success in the Supreme Court in the case of Henderson v. Dorset Healthcare NHS Foundation Trust [2020] UKSC 43, it now appears likely that the illegality defence will apply to bar all civil claims brought by perpetrators of killings, regardless of the criminal disposal.
What was the case about?
The circumstances giving rise to Mr Lewis-Ranwell's case are tragic for all those who have been touched by it and the following discussion should be viewed through that sensitive lens.
Mr Lewis-Ranwell had a history of severe mental illness. He had been detained by the local Police in February 2019 after he had started to behave strangely, including stealing items from a farm and releasing animals. He was charged with burglary before being released.
He was then re-arrested later that day after injuring an elderly man with a saw on the mistaken belief that the man was a paedophile. He was charged with grievous bodily harm and assessed by a number of mental health professionals, for whom the defendants/appellants were responsible, but it was ultimately considered that the claimant did not require a Mental Health Act assessment and he was released on bail the following morning. Later that day he violently killed three elderly men, under the delusional belief that they were paedophiles.
Mr Lewis-Ranwell was later charged with murder but was found not guilty by reason of insanity. Specifically, it was found that whilst he knew the nature and the quality of his acts, he did not know what he was doing was wrong.
Mr Lewis-Ranwell later brought a claim for compensation for negligence as well as for damages under the Human Rights Act for breaches of Articles 3 (prohibition of torture) and 8 (right to respect for private and family life) of the European Convention on Human Rights.
Mr Lewis-Ranwell’s case against the defendants was that if he had been properly assessed whilst in custody he would have been admitted to hospital for treatment and therefore he would not have injured or killed anyone. He claimed compensation for, amongst other things, an exacerbation of his psychiatric condition and a prolonged loss of liberty whilst he is detained under a Hospital Order at Broadmoor Hospital.
Having served defences to the claim (all of which denied liability), three of the four defendants, including the Trust, made an application for Mr Lewis-Ranwell's common law negligence claim to be struck out on the basis that it was barred by the illegality defence, a defence with its origins in case law from the 1700s; as it was put back in 1775: "No Court will lend its aid to a man who founds his cause of action upon an immoral or an illegal act." It is well-established that the illegality defence does not apply to claims made under the Human Rights Act, and therefore the defendants' strike out applications did not extend to that aspect of Mr Lewis-Ranwell's claim.
The question for the Supreme Court was, therefore: does the illegality defence bar a common law claim for damages by someone who has been found not guilty of murder by reason of insanity by the criminal courts?
The Supreme Court has considered whether killings engage the illegality defence before in the context of a clinical negligence claim; Henderson v. Dorset Healthcare NHS Foundation Trust [2020] UKSC 43, another case in which DAC Beachcroft acted for the successful defendant, concerned the partial defence to murder of diminished responsibility, which reduced Ecila Henderson's criminal offence in that case to one of manslaughter. Ms Henderson pleaded guilty to that criminal offence, i.e. manslaughter by reason of diminished responsibility, and the Supreme Court later found that the illegality defence applied to bar all the heads of loss in her subsequent civil claim.
There was (until now), however, no precedent on whether the illegality defence was engaged in circumstances where someone had been found not guilty of murder by reason of insanity.
What did the Supreme Court decide?
The Supreme Court has unanimously held that the illegality defence does apply in these circumstances, and therefore Mr Lewis-Ranwell's common law negligence claim is barred.
In weighing the relevant public policy considerations in the balance and concluding that the common law claim should be barred, the Supreme Court found, amongst other things, that:
- The presence of criminality is not a decisive consideration in whether the illegality defence is engaged. The question is whether there is an "immoral or illegal" act engaging the interests of the State or the public interest. In the context of Mr Lewis-Ranwell's case, killing another human being without lawful justification breaches a fundamental moral rule in society: you shall not kill. His actions were unlawful conduct for the purpose of engaging the illegality defence.
- To allow Mr Lewis-Ranwell's civil claim to proceed would give rise to a series of inconsistencies which would damage the integrity of the law and the legal system. For example, it would be inconsistent for a civil court to order the payment of compensation to Mr Lewis-Ranwell for the consequences of his lawful detention (under a Hospital Order) ordered by a criminal court.
- Public confidence in the integrity of the legal system would be adversely affected if Mr Lewis-Ranwell was permitted to recover damages for his actions.
- Where the brutal killing of three innocent men is of the utmost seriousness, it would not be disproportionate to bar his common law claim.
Discussion
The effect of the Supreme Court's ruling is that subject to the facts of the particular case, the illegality defence is, in principle, available to defendants in negligence cases, even where the claimant has been found not guilty of a criminal offence by reason of insanity and may therefore have little or no responsibility for their actions due to mental illness.
Certainly, it will now likely apply in all claims brought by perpetrators of killings, as it already does in cases where claimants have been convicted of diminished responsibility manslaughter.
