Illegality Bars Negligence Claims by a Killer Found Not Guilty by Reason of Insanity: Unlawful Killing Engages ex turpi causa Despite No Criminal Responsibility

1. Introduction

This appeal arose from strike-out/summary judgment applications in a civil negligence claim brought by Alexander Lewis-Ranwell (“the claimant”), who unlawfully killed three men during an acute psychotic episode in February 2019. At his criminal trial he was found not guilty of murder by reason of insanity and made subject to a hospital order with restrictions under sections 37 and 41 of the Mental Health Act 1983, imposed mandatorily following the special verdict.

He sued multiple defendants—G4S Health Services (UK) Limited, Devon Partnership NHS Trust, and Devon County Council (among others)— alleging negligent failures in custodial forensic medical services, Liaison and Diversion services, and Mental Health Act assessment arrangements. He claimed that, but for those failures, he would have been detained and treated in hospital before the killings, avoiding (among other consequences) his later detention, reputational damage, loss of earnings, care needs, and civil liability to the victims.

The core issue was whether—given the insanity verdict—the claimant’s pleaded heads of loss in negligence were barred by the illegality defence (ex turpi causa). The Human Rights Act claims were not pursued as barred by illegality, so the Supreme Court focused on negligence.

2. Summary of the Judgment

The Supreme Court allowed the appeal and held that the illegality defence is engaged and, applying the structured approach from Patel v Mirza [2016] UKSC 42; [2017] AC 467, it bars the claimant’s negligence claim.

The Court rejected the Court of Appeal majority’s “bright line” approach that would have treated the absence of criminal responsibility (insanity) as decisive. Instead, it held that unlawful killing, even without criminal responsibility, engages public policy concerns (coherence, consistency, integrity of the legal system), and that permitting recovery for detention and its consequences would be incoherent and damaging to public confidence.

3. Analysis

3.1 The New Principle / Clarified Rule

3.2 Precedents Cited (and How They Shaped the Outcome)

(a) Foundational and methodological authorities

• Holman v Johnson (1775) 1 Cowp 341: The Court reaffirmed Lord Mansfield’s maxim that courts will not assist a claimant who founds a cause of action on “an immoral or an illegal act”. This anchored the defence as one of public policy, not a merits-based balancing between parties.
• Tinsley v Milligan [1994] 1 AC 340: The “reliance test” (whether the claimant must plead or rely on illegality) was described as the former organizing principle. The Supreme Court treated it as historically important but not controlling after Patel v Mirza.
• Patel v Mirza [2016] UKSC 42; [2017] AC 467: This was the decisive framework. The Court applied Lord Toulson’s “trio”: (a) purpose of the prohibition; (b) countervailing policies; (c) proportionality—each directed to whether allowing the claim would harm the integrity of the legal system.
• Grondona v Stoffel & Co [2020] UKSC 42; [2021] AC 540: Used to emphasise that the Patel factors are assessed at a relatively high level of generality at stages (a) and (b), with detail more prominent at stage (c), all in service of the “integrity/coherence” question.

(b) The “unlawful killing and detention” line: the gravitational centre

• Gray v Thames Trains Ltd [2009] UKHL 33; [2009] AC 1339: The Court treated Gray as a policy-based decision (not reliance-based) and compatible with Patel. It adopted Gray’s two formulations:
  • Narrow rule: no recovery for loss consequent on a sentence/disposal imposed for one’s own unlawful act.
  • Wider rule: no recovery for loss that is the consequence of one’s own criminal conduct, because compensating it offends public notions and legal coherence.
  Although Gray involved manslaughter by diminished responsibility, the Supreme Court in Lewis-Ranwell held that the relevant public policy (coherence and integrity) remains engaged even where criminal responsibility is absent.
• Henderson v Dorset Healthcare University NHS Foundation Trust [2020] UKSC 43; [2021] AC 563: The Court relied heavily on Henderson as confirming Gray as “Patel-compliant” and as insisting that decided cases remain valuable unless inconsistent with Patel. Importantly, Lewis-Ranwell rejected the Court of Appeal’s reading that Henderson implied insanity would avoid illegality: the Supreme Court held that knowledge of wrongfulness in Henderson was “additional”, not central, and that Henderson’s core was coherence/integrity.
• Clunis v Camden and Islington Health Authority [1998] QB 978: The Supreme Court agreed with the ratio that courts should not be used to enforce obligations arising out of the claimant’s own unlawful homicide, but expressly disagreed with Clunis’s obiter suggestion that insanity might change the result. That obiter was treated as a product of earlier “turpitude/reliance” thinking.
• Traylor v Kent and Medway NHS Social Care Partnership Trust [2022] 4 WLR 35: Johnson J’s obiter view (that insanity would tend against illegality) was noted but not adopted; the Supreme Court’s approach displaced it.

(c) Threshold and scope: “criminal vs unlawful”, and coherence across legal fields

• Les Laboratoires Servier v Apotex Inc [2014] UKSC 55; [2015] AC 430: Used to contrast Lord Sumption’s “criminal or quasi-criminal” threshold with the policy-led approach that prevailed in Patel. Lewis-Ranwell did not adopt a rigid “criminal responsibility” threshold; instead it asked whether the conduct engages the public interest and coherence concerns.
• Hounga v Allen [2014] UKSC 47; [2014] 1 WLR 2889 and Bilta (UK) Ltd v Nazir (No 2) [2015] UKSC 23; [2016] AC 1: Cited as steps in the movement away from mechanical tests toward policy-based analysis, culminating in Patel.
• Hall v Hebert [1993] 2 SCR 159: McLachlin J’s articulation—“the law refuses to give by its right hand what it takes away by its left”—was used to frame the core concern: internal harmony across criminal law, tort, and public protection regimes.

(d) Tort doctrines used to demonstrate “incoherence” if recovery were allowed

• Weaver v Ward (1616) Hob 134 and Morriss v Marsden [1952] 1 All ER 925: Cited for the proposition that insanity is not a defence to trespass to the person/battery—supporting the Court’s view that civil liability can attach notwithstanding insanity.
• Dunnage v Randall [2015] EWCA Civ 673; [2016] QB 639: Cited to show that the negligence standard is objective and does not adjust for insanity—reinforcing that tort law would hold the claimant responsible to victims, making it incoherent to let him shift that civil responsibility to healthcare/public authorities via negligence damages/indemnity.
• Meah v McCreamer (No 2) [1986] 1 All ER 943: Raised (in defendants’ submissions) as supporting remoteness barriers to indemnity-type claims; while the Supreme Court decided on public policy, it also flagged doctrinal obstacles (duty, remoteness, causation) that would likely defeat an indemnity claim.
• Palmer v Tees Health Authority [2000] PIQR P1 and Robinson v Chief Constable of West Yorkshire Police [2018] UKSC 4; [2018] AC 736: Cited to illustrate that the victims’ estates would likely struggle to sue these defendants due to the absence of a duty to third-party victims, and that it would look unjust/incoherent if the killer could sue where victims could not.

(e) Criminal law authorities framing the insanity context (without making it determinative)

• M'Naghten's case (1843) 10 Cl & Fin 200, R v Keal [2022] EWCA Crim 341; [2022] 4 WLR 41: Used to describe the insanity test and the later clarification that “wrong” can be moral wrong, while noting the claimant’s trial used the pre-Keal direction.
• Loake v Director of Public Prosecutions [2017] EWHC 2855 (Admin); [2018] QB 998: Cited to show that a defendant may have mens rea yet be not guilty by reason of insanity (depending on which limb of M’Naghten applies).
• Attorney-General's Reference (No 3 of 1998) [2000] QB 401 and R v Antoine [2001] 1 AC 340: Used to explain that, following insanity evidence, the prosecution must still prove the actus reus (and negate relevant defences).

(f) Overseas authority

• Hunter Area Health Service v Presland [2005] NSWCA 33; (2005) 63 NSWLR 22: Treated as closely analogous: unlawful homicide with mental illness acquittal; majority refused recovery for detention consequences. The Supreme Court aligned with the “coherence/public policy” thrust (even though the Australian analysis was framed as duty scope).
• Ellis v Counties Manukau District Health Board [2006] NZHC 826; [2007] 1 NZLR 196: Similar outcome in New Zealand (strike-out), again reflecting reluctance to impose liability for failing to detain.
• Barker v Barker 2022 ONCA 567: Noted as Canadian support for applying illegality even absent guilt/moral responsibility, to protect integrity of the legal system.
• US decisions (Lingle v Berrien County 522 NW 2d 641 (Mich App 1994), Boruschewitz v Kirts 554 NE 2d 1112 (Ill App 1990), Bruscato v O'Brien 705 SE 2d 275 (Ga App 2010)) were treated as mixed persuasive material, not determinative.

3.3 Legal Reasoning (How the Court Reached its Result)

(A) The threshold question: is illegality “engaged” at all?

The Supreme Court first insisted on a threshold: not every unlawful act should trigger the doctrine. But it held that the claimant’s conduct plainly crossed it because:

• The special verdict established he did the acts (killed three men) even though he was not criminally responsible.
• Unlawful killing engages the public interest (sanctity of life, public protection) in a way that ordinary civil wrongs between private parties do not.
• The Court rejected the Court of Appeal’s approach that civil illegality should track the criminal law’s “bright line” (diminished responsibility vs insanity). That distinction was treated as a point on a spectrum of impairment, not a determinant of civil public policy.

In short: the threshold is met by unlawful homicide as conduct engaging the interests of the state/public, regardless of criminal responsibility.

(B) The Patel v Mirza assessment

Stage (a): purpose of the prohibition, and whether denial enhances it

The prohibition was framed at its highest level: “you shall not kill”—preserving life and respect for its sanctity, condemning unlawful killing, protecting the public, and (where applicable) deterrence.

The Court considered that allowing the claim would create damaging incoherences, including:

• Incoherence with the criminal court’s disposal: the claimant’s detention under a hospital/restriction order is a lawful, mandatory protective response to the killings; compensating him for that detention would “give with the right hand what it took away with the left”.
• Incoherence within tort: the claimant remains liable in battery to victims’ estates/dependants despite insanity; allowing him to recover damages/indemnity from others for the consequences of his own unlawful battery would distort tort responsibility.
• Victims’ position: victims would likely face major obstacles suing these defendants (no duty to third parties), yet the killer could recover—an outcome the Court saw as corrosive to legitimacy.
• The indemnity head: permitting the claimant to be indemnified for liability to victims would be especially disreputable, effectively shifting civil responsibility for grave wrongdoing.

Public confidence was treated as closely aligned with coherence: the Court doubted that ordinary “right-thinking” members of the public would see it as acceptable for the killer (even if insane) to recover compensation for the consequences of the killings, especially from public funds.

Stage (b): countervailing policies that denial would undermine

The Court accepted the general value of courts adjudicating civil wrongs and the potential learning/accountability functions of litigation. But it considered those aims could be served by other mechanisms (including the inquest process and prevention of future deaths reports), and did not outweigh the stage (a) integrity concerns.

It also clarified that denial of the claim is not a “punishment” inconsistent with the criminal verdict; it is a structural consequence to prevent incoherence.

Stage (c): proportionality

The Court found denial proportionate given:

• Seriousness: the brutal killing of three innocent men is of the utmost gravity.
• Centrality: the unlawful killings were central to every pleaded head of loss and the effective cause of them.
• Intentionality/unlawfulness: even if insanity removes criminal responsibility, the acts remain unlawful killings and intentional attacks in fact.

3.4 Impact (Why This Decision Matters)

• Insanity is not a “safe harbour” from illegality in negligence: the decision closes off an argument that an insanity verdict, by itself, prevents the illegality defence from operating in civil claims tied to unlawful homicide.
• Re-centres illegality on coherence rather than culpability: while responsibility and turpitude may matter at the margins (especially in proportionality), the controlling question is whether allowing the claim damages integrity/coherence.
• Broadens the “threshold” conception: the defence can be engaged by conduct that is unlawful in a public-interest sense even without criminal responsibility, especially where it triggers protective state detention.
• Forecloses indemnity strategies: claims seeking indemnities against victims’ civil actions are strongly indicated to be barred (and, additionally, vulnerable on duty/remoteness/causation grounds).
• Practical litigation effect: healthcare/police-adjacent negligence claims by persons subject to forensic disposals after unlawful violence will face a robust illegality defence where the loss is rooted in the violence. Future disputes may concentrate on whether losses can be conceptually separated from the unlawful act (the “head-by-head” approach seen in Hewison v Meridian Shipping Services PTE Ltd and Ali v HSF Logistics Polska sp z oo, both cited for remedial flexibility).

4. Complex Concepts Simplified

4.1 “Not guilty by reason of insanity” (what it means—and what it does not mean)

The special verdict means the defendant is not criminally responsible under the M’Naghten rules, but it does not mean the killing is “lawful” or “justified”. It triggers court powers (and in murder cases, a mandatory disposal) aimed at public protection, not punishment.

4.2 The illegality defence after Patel v Mirza

The illegality defence is no longer a mechanical question of whether the claimant must “rely on” illegality. It is a structured public policy inquiry aimed at preventing the legal system contradicting itself—especially where one part of the law condemns/controls conduct and another would effectively compensate or underwrite its consequences.

4.3 Why tort “responsibility” matters even if criminal responsibility is absent

Tort law can impose liability even where criminal law excuses the defendant. The judgment relied on the point that insanity is not generally a defence to battery, and negligence uses an objective standard. That civil baseline made it harder to accept that the claimant could shift civil consequences to the defendants without damaging coherence.

5. Conclusion

Lewis-Ranwell establishes that the illegality defence may bar a negligence claim even where the claimant was found not guilty by reason of insanity, where the losses claimed flow from unlawful killing and the protective detention that follows. The Supreme Court’s reasoning is anchored in Patel v Mirza: the decisive concern is the integrity, coherence, and credibility of the legal system, not a bright-line replication of criminal responsibility categories.