Alexander Lewis-Ranwell v G4S Health Services (UK) Ltd & Ors

The Court of Appeal (Majority: Underhill LJ and Dame Victoria Sharp P) held that the common‑law illegality defence (ex turpi causa) is unavailable to bar a claimant’s negligence claim where the claimant has been found not guilty by reason of insanity because, under the M’Naghten rules, the claimant lacked the requisite knowledge that his acts were wrong and therefore the acts lacked the element of turpitude relied on by the defence. The court applied the Patel v Mirza framework but emphasised existing authorities distinguishing diminished responsibility (where criminal responsibility remains) from insanity (where it is extinguished) and concluded the policy considerations supporting a bar did not outweigh the claimant’s right to compensation.

The court therefore dismissed the appellants’ strike‑out appeals against Garnham J’s order (EWHC), leaving negligence and Human Rights Act (s.7) claims to proceed; causation, contributory negligence and quantum were left to be tried.

Background and facts:

• The respondent (born c.1992) had a history of psychotic illness. During a serious psychotic episode on 10 February 2019 he attacked and killed three elderly men and injured others. At trial he was found not guilty by reason of insanity and was detained under hospital orders with restrictions pursuant to sections 37 and 41 of the Mental Health Act 1983.
• In the days before the killings he had been detained twice by the police and released; during those detentions he displayed violent, delusional behaviour and was seen or contacted by mental‑health professionals employed by G4S and the local NHS trust. A Mental Health Act assessment was discussed but not arranged.

Procedural posture and relief sought:

• In February 2020 the claimant issued civil proceedings in the High Court against G4S, the Police, Devon Partnership NHS Trust and Devon County Council, pleading negligence and a claim under s.7 Human Rights Act 1998 (breach of Convention rights). He sought damages for personal injury, loss of liberty, loss of reputation, pecuniary losses and an indemnity for any claims by his victims.
• The three defendants (G4S, the Trust and the Council) applied to strike out the negligence claims on the basis of the illegality defence (ex turpi causa). Garnham J (King’s Bench) dismissed the strike‑out applications ([2022] EWHC 1213 (QB)). The defendants appealed to the Court of Appeal.

Issues for decision:

• Whether the illegality defence operates to bar a negligence claim where the claimant committed unlawful killings while insane and was acquitted by reason of insanity (i.e. whether lack of knowledge of wrongfulness excludes the defence).
• How established authorities on ex turpi causa and on liability of the mentally ill in tort (including Clunis, Gray, Henderson, Dunnage, Morriss and others), and the policy approach in Patel v Mirza, bear on that question.

Court’s reasoning (concise):

• The court reviewed the M’Naghten rules and distinguished cases of diminished responsibility (partial criminal liability leading to manslaughter) from true insanity cases (where the defendant did not know the act was wrong).
• It noted established tort authority (Morriss; Dunnage) that mental illness is generally not a defence to tort liability, and reviewed the illegality doctrine as reformulated in Patel v Mirza (a policy‑based balancing exercise: purpose of prohibition; other public policies; and proportionality).
• The majority concluded that the ex turpi causa defence traditionally requires some knowledge or moral culpability (turpitude). A special verdict of not guilty by reason of insanity establishes lack of that knowledge; accordingly the defence does not, as a matter of law, bar a negligence claim that is founded on the consequences of unlawful acts committed when the claimant lacked awareness that they were wrong.
• The court weighed countervailing public‑policy considerations relied on by the appellants (consistency with criminal law; public confidence in the legal system; impact on public funds; deterrence) and concluded they did not justify denying recovery in an insanity case. The majority therefore dismissed the appeal and allowed the negligence claim to proceed to trial on liability, causation and quantum.

Dissent: Andrews LJ would have allowed the appeal, emphasising coherence between civil and criminal liability and the inappropriateness of permitting a person who deliberately committed fatal torts to shift legal responsibility to others.

Appeal dismissed. The majority held that the illegality defence (ex turpi causa) does not bar a negligence claim where the claimant was found not guilty by reason of insanity because the special verdict establishes lack of knowledge that the conduct was wrong (no requisite turpitude); public‑policy considerations (consistency and public confidence) did not justify denying recovery in such an insanity case. The negligence claims therefore remain to be litigated on liability, causation and quantum.

Appeal from the High Court (King's Bench Division) before Garnham J, who on 20 May 2022 dismissed strike‑out applications ([2022] EWHC 1213 (QB)). The defendants appealed to the Court of Appeal, which delivered judgment at [2024] EWCA Civ 138 (20 February 2024).