If you do not know you are doing wrong, can you sue for not being prevented from doing it?

If you have been found by a criminal court that you did not know what you were doing was wrong when you killed someone, should you able to sue those statutorily charged with assessing your mental health for failing to stop you?

That was the stark question before the Court of Appeal in Alexander Lewis-Ranwell v G4S Health Services (UK) Ltd & Ors [2024] EWCA Civ 138.   On 10 February 2019, in the course of a serious psychotic episode, the claimant had attacked and killed three elderly men in their homes in Exeter in the delusional belief that they were paedophiles. He was charged with murder but following a trial in Exeter Crown Court he was found not guilty by reason of insanity: in law, this meant that because of his mental illness he did not know at the time of the killings that what he was doing was wrong. He was ordered to be detained in Broadmoor Hospital pursuant to a hospital order with restrictions under sections 37 and 41 of the Mental Health Act 1983.  In the two days before the killings he had twice been arrested, and detained for some time before being released. During both periods of detention the claimant behaved violently and erratically and was apparently mentally very unwell. He was seen or spoken to by mental health professionals employed by G4S Health Services (UK) Ltd and Devon Partnership NHS Trust. A face to face assessment by the mental health nurse employed by the Liaison and Diversion Service of the NHS Trust was discussed but did not take place. The need for a Mental Health Act Assessment was discussed with an Approved Mental Health Professional employed by Devon County Council but was not arranged.

On 4 February 2020 the claimant commenced proceedings in the High Court against G4S, the Police, the Trust and the Council. In broad terms it was his case that it should have been obvious to all concerned during both detentions that if he were released there was a real risk that he would injure other people, and that the necessary steps should have been taken to keep him in detention until it was safe for him to be released. The claims were advanced in negligence and under section 7 of the Human Rights Act 1998. The heads of damage pleaded in the Particulars of Claim were for personal injury, loss of liberty, loss of reputation, and “pecuniary losses”. The claimant also sought an indemnity in respect of any claims brought against him “as a consequence of his violence towards others on 9-11 February 2019”.

All of the organisations involved (bar the police) sought to have the claim struck out on the basis, broadly, that they were entitled to rely “the illegality defence” – that is, the rule that the Court will not entertain a claim which is founded on a claimant’s own unlawful act – because the claim was based on the consequences of the claimant’s three unlawful homicides.[1]

As Underhill LJ (one of two judges in the majority, along with Andrews LJ) noted, the question of whether the illegality defence operated in a case where the claimant was insane at the time that he or she did the unlawful act was not the subject of any binding authority.  In Clunis v Camden and Islington Health Authority [1998] QB 978, the Court of Appeal held that a mentally ill person who had been convicted of manslaughter by reason of diminished responsibility was barred by illegality principle from bringing a claim against his doctors for negligent treatment which was said to have caused or contributed to his committing the offence; and that decision had since been upheld by the House of Lords in Gray v Thames Trains Ltd [2009] UKHL 33, and by the Supreme Court in Henderson v Dorset Healthcare University NHS Foundation Trust [2020] UKSC 43 However, as Underhill LJ identified, the reasoning in those decisions, though clearly relevant to this case, was not determinative because diminished responsibility is not the same as insanity.   The issue had, however, been directly considered in some U.S. and Commonwealth cases, and also in a recent decision of the High Court, Traylor v Kent & Medway NHS Social Care Partnership Trust [2022] EWHC 260 (QB).

Underhill LJ considered that the public authorities should not be able to rely on the illegality defence, and after an extensive review of the case-law, took each the arguments in favour of the defence in turn to explain why they did not avail the public authorities.

First, as regards the inconsistency that would arguably arise between the civil and criminal law, he accepted the claimant’s case that the “verdict of not guilty by reason of insanity was an acquittal. Accordingly the law has not treated him as criminally responsible for his actions, and there is no inconsistency in allowing him to recover for the loss that he has suffered in consequence of them” (paragraph 93).  He noted that “[t]hat approach also seems to me to accord with the fundamental justice of the matter. At a superficial level you could still say that it was inconsistent to allow a person to recover for the consequences of an unlawful act which they have done. But at a more fundamental level the criminal law is concerned not with acts as such but with personal responsibility for those acts, and a difference in treatment based on differences in personal responsibility cannot be said … to undermine ‘the integrity of the justice system.’ This reflects the basic perception reflected in the authorities […] based on the requirement of moral culpability” (paragraph 96).  Underhill LJ emphasised that he was only dealing at this stage with the inconsistency principle, and that the argument that the claimant should not be entitled to recover compensation for the consequences of his criminal act (albeit one for which he had no criminal responsibility) could still be deployed in the context of the public confidence principle, considered further below.

Second, there was said to be an inconsistency within the civil law that it was clearly established by case-law that the claimant’s insanity would be no defence to any action in tort that his victims’ families might bring.  However, Underhill LJ considered, “[t]he question of the liability of the Claimant to his victims for the injury which he caused them is self-evidently different from the question of the liability of the Appellants for the loss which they have caused him. In the former case justice requires that the interest of the victim in receiving compensation comes before any question of moral culpabilityIn the latter it is the Claimant who is the victim of wrongdoing and the question whether he should nevertheless be denied recovery because his loss was the result of a criminal act has to be considered in that quite different context. Again, I am not saying that it has to be answered in his favour, only that to allow recovery would not be inconsistent with the rule that his insanity does not preclude his liability to his victims.”

Third, Underhill LJ considered the public confidence principle, identified in the Henderson case as being the potential that allowing a claimant to be compensated for the consequences of his own criminal conduct would risk bringing the law into disrepute and diminishing respect for it because that is an outcome of which public opinion would be likely to disapprove. He noted at paragraph 103 that:

In my view it is this principle which is at the heart of this appeal, as it was for Santow JA in [the Australian case of ] Presland, and I have not found it easy to decide whether it should operate in this case. I do not doubt that it would – at least as a first reaction – stick in the throats of many people that someone who has unlawfully killed three innocent strangers should receive compensation for the loss of liberty which is a consequence of those killings, however insane he was and however negligent his treatment had been. To the extent that that reaction reflects, in Santow JA’s language, “considered community values”, we should be very slow to disregard it: the law ought so far as possible to give effect to such values.

However, Underhill LJ came to the conclusion that:

104.  […] although that first reaction is entirely understandable, the values of our society are not reflected by debarring a claimant from seeking compensation in this kind of case. It is necessary, as Santow JA accepted, to go beyond “instinctive recoil” and to consider what justice truly requires in a situation which most humane and fair-minded people would recognise as far from straightforward. Taking that approach, although of course those who are killed or injured must always be treated as the primary victims, it is fair to recognise that the killer also may be a victim if they were suffering from serious mental illness and were let down by those responsible for their care. I rather suspect that some such view underlies the observations of the jury at the Claimant’s trial which I quote at para. 11 above.[2] But, whether it does or not, I believe that the considered view of right-thinking people would be that someone who was indeed insane should not be debarred from compensation for the consequences of their doing an unlawful act which they did not know was wrong and for which they therefore had no moral culpability. As we have seen, the law does not generally apply the illegality defence where the claimant does not know that what they are doing is wrong and has no moral culpability; and in my view that reflects ordinary and comprehensible principles of fairness. I do not believe that it is rational, or would accord with community values, that the position should be different where the claimant’s lack of knowledge or culpability was the result of insanity. In short, I would align myself with the approach taken by Spigelman CJ at para. 95 of his judgment in Presland: see para. 55 above.

Two further potential anomalies were pointed out by the public bodies in support of their argument that the law would be brought into disrepute.  The general one was that claimants would be entitled to claim compensation from their doctors for what they had lost as a result of not being prevented from committing their unlawful acts, the victims of those acts (or their estates or dependants) would have no claim against the doctors.  Underhill LJ was:

107. […] prepared to assume that at least in the generality of cases victims in a situation such as the present would have no right to recover against the authorities whose negligence had allowed the attack to take place. But I do not accept that that gives rise to an anomaly. Victims may not have a right to compensation against the doctors, but they have a straightforward claim against their assailant, whose insanity would be no defence to a civil claim for assault.  It is true that, unlike a doctor or health authority, the assailant may not be in a position to meet a substantial award of damages. However, as we have seen, one of the heads of damage claimed by the Claimant in this case is an indemnity against any liability to his victims. I can see no reason why that would not be an admissible head of claim; and, if it is, it would afford a route by which victims could be assured of payment of any damages that they were awarded. However, Ms Ayling did not accept that a claim for such an indemnity would lie, though she did not advance any developed reason for that position. In the absence of full argument I am not prepared definitively to decide the point. But even if the claimant were not entitled to such an indemnity, the fact that they might not be able to meet any award of damages to the victim does not seem to me to be a principled reason for denying them recovery for their own loss.

The more specific anomaly would arise in the case where the victim of the claimant’s unlawful act was also the defendant – for instance where a mentally ill patient attacked the negligent doctor.  Underhill LJ fully accepted that:

110. […] seems unjust that someone who has suffered unlawful injury at the hands of another can be required to pay damages to them for the consequences that they have suffered as a result of inflicting that injury. Of course the victim would have a cross-claim, but even if that exceeded the value of the claimant’s claim, so that there was no net liability, their net recovery would necessarily be less than the full compensation for their loss. The position would be worse still if the claimant, as in this case, claimed an indemnity against any such liability: that would on the face of it reduce the victim’s recovery to nil while still leaving them liable for the claimant’s loss. (It is true that they might be insured against their liability to the claimant – in my two examples, both the doctor and the driver would almost certainly be insured – but that ought not to affect the position in principle.)

111. I do not, however, believe that the problems that would arise in that scenario are a reason for barring a claim in the typical case where, as here, the defendant is not a victim of the claimant’s unlawful act. I ought not to seek to determine in advance how the Court would address such a situation; but since we are concerned with questions of public policy, it would have the tools to produce a just outcome.

Fourth, Underhill LJ considered two other considerations that had also been raised in Henderson: (a) the impact on NHS funding of allowing a claim of the present kind; and (b) deterring unlawful killing and providing protection to the public, there being no more important right to protect than the right to life.  Whilst Underhill LJ agreed that they appeared to be in play, he considered that the question was whether it was proportionate to treat them as outweighing the public interest in claimants in insanity cases receiving due compensation for the wrong that they have suffered.  He did not believe that it was:

116. The balance is quite different from in the diminished responsibility cases because the claimant has no moral culpability. That point is clearly made if one looks at how Lord Hamblen struck the balance at paras. 138-143 in Henderson. In those paragraphs he emphasises the importance of the fact that the claimant knew that what she was doing was legally and morally wrong: see paras. 139 and 142. In the absence of that element, and where, essentially for that reason, the consistency and public confidence principles are, as I would hold, not engaged, I do not believe that either the impact on NHS resources or the general deterrent effect of a rule against recovery could justify the denial of the claim in these proceedings.

A final consideration was the fact identified by the appellant public bodies that there was no sharp distinction between a finding of diminished responsibility and a finding of insanity: the distinction is one of degree only:

117. […] That may be so, but the criminal law proceeds on the basis that the distinction is nevertheless real and that in any given case it will be possible to say on which side of the M’Naghtenline the defendant falls. That being the case, there is nothing irrational about the application of the illegality defence depending on the selfsame distinction. If I had any unease about this aspect, it would, rather, be about the possibility that in some cases the distinction may reflect not a finding by a court but a forensic choice by the defendant or their advisers. Pleas of not guilty by reason of insanity are in practice rare; and there must be cases where a defendant tenders, and the Crown accepts, a plea of manslaughter by reason of diminished responsibility where the facts might arguably have justified a special verdict (Hendersonmay be an example). But if that results in the illegality defence being unavailable in some cases where it might have been available if the defendant had made a different choice I do not think that can affect the decision in principle which we have to make.

Whilst Underhill LJ identified (at paragraph 119) that he did not consider the question as an easy one, he therefore allowed the appeal.

Dame Victoria Sharp P gave a shorter judgment explaining her reasoning for allowing the appeal, her central reasoning being that each of the key English cases:

161. […] draws a coherent and bright line distinction for the purposes of the ex turpi causa doctrine, between those who are criminally responsible for their acts whether fully or partially, and those who are not responsible for their acts because they do not know what they are doing is morally and legally wrong. In my judgment, this common thread running through the criminal and civil law, is consistent with principle, a proper understanding of the true implications of acute mental illness and is one that would not offend the sensibilities of ordinary right-thinking members of the public or undermine public confidence in the law.

Andrews LJ dissented, finding herself unable to agree with the majority that:

122. […] a lack of knowledge or understanding by a person who intentionally takes the life of another human being that what he was doing was wrong is a sound and principled basis for allowing that person to make a claim in negligence against someone for putting them in a position which enabled them to commit an act which was both deliberate and tortious.

123. I agree with Underhill LJ that in an era where there is much greater understanding of mental health issues, it is fair to recognise that, as well as the primary victims, the killer also may be a victim, if they were suffering from serious mental illness and were let down by those responsible for their care. However, I am not persuaded that an absence of the state of knowledge of wrongdoing, which would afford the mentally ill perpetrator of a deliberate fatal assault a complete defence to criminal liability for murder or manslaughter, justifies drawing a bright line between the present case and similarly tragic cases such as Clunis, Gray and Henderson.

124. There are all kinds of reasons why a defendant suffering from a serious mental illness who faces a charge of murder might prefer to opt for running the partial defence of diminished responsibility rather than pleading insanity, even though it may be open to them to do so. The most obvious of these is the prospect of indefinite incarceration in a secure mental health unit. Moreover, it is not difficult to conceive of examples of situations where a person who is guilty of the criminal offences of murder or manslaughter, or causing death by careless driving, might be regarded by the public as less blameworthy for the death than a person in the position of the Claimant, who intended to kill his victims. Yet such a person would be precluded by their conviction from making a claim of this nature even if they were seriously mentally unwell at the time.


137,  I have not reached this conclusion lightly. However it does seem to me that there is nothing disproportionate about precluding someone who intended to kill, and did so, from bringing a claim in negligence in reliance on that deliberate and unlawful act, and that the policy rule preventing such claims from being made should not rest on nice distinctions between having little or no personal responsibility for the killing because of the state of the claimant’s mental health at the time. For those reasons, I would have allowed this appeal.


It is very important to make clear that the decision of the Court of Appeal is not that the public authorities did, in fact, fail in their duties towards the claimant.  Rather, it was whether, as a matter of principle, the claimant could even bring his claim.  Further, as Underhill LJ identified, there also remains in play issues such as whether his contributory negligence should eliminate in whole or in part any obligation on their part to pay him damages.  Furthermore, it is important to remember in any commentary or discussion of the case that underpinning it is a tragedy where three entirely innocent people were killed.

However, given the wider implications of the analysis of the law in play, the determination of the majority to carry through the logical implications of the meaning of a finding of not guilty by reason of insanity – i.e. that a person is truly to be taken not to be responsible for their actions – stands out at a time of considerable media interest (to put it neutrally) in the implications of a person being found not guilty by reason of insanity as a result of the Valdo Caldocane case.  It is perhaps not surprising that that all three of the judges found the case a difficult one, and that Underhill LJ identified that the approach that underpinned it would – at least by way of first reaction – stick in the throats of many.

For those steeped in matters of mental health law from the disability rights angle, one striking feature of the case was the absence of discussion of the UN Convention on the Rights of Persons with Disabilities.  It is perhaps not entirely surprising this was the case, given the limited traction it has had in most areas of the law, both generally across the world, and specifically within England and Wales.  This lack of traction, in England and Wales, may in part be down to the fact that it is not “domesticated” in the same way as the ECHR, so expresses a state-level commitment rather than imposing direct obligations on public bodies and courts.  However, even if not part of English law, the CRPD is undoubtedly a key part of the modern context within which the approach to mental illness is considered,[3] a context which appears to have played a part in the thinking of the majority. And, given that the Court of Appeal were grappling with principles, the CRPD might be thought to have provided a useful stress-test of those principles.

On one view, it might be thought that, albeit perhaps unknowingly, Andrews LJ’s dissent reflects the most CRPD-compliant approach to the difficult question before the court.  Put shortly, if a central tenet of the right to equal recognition before the law in Article 12 CRPD[4] is that those with disabilities should not be denied agency on the basis of their impairments, then it might be said that it flows that they should not be identified as lacking responsibility for their actions when they act upon that agency: no matter the consequences.  That would, in turn, seem to point to a conclusion that the illegality defence should be available in all cases where the person’s actions were both intentional and wrongful (even if that ‘intention’ was based upon delusional beliefs).

In saying this, I should say that I am aware that some might contend that: (1) none of the public authorities should have had the power to detain the claimant prior to his attacks on the basis of his mental ill-health, such that his claim should fail at the very first base; and (2) the CRPD would dictate the abolition of the very concept of a defence of not guilty by reason of insanity, such that he should, in fact, have been convicted of their murders.  Both of these points in different ways show the complexities of the CRPD, especially as interpreted by the Committee on the Rights of Persons with Disabilities.   And they arguably also show the limits of the ‘abolitionist’ arguments advanced by the Committee and / or those associated with it.[5]  But if the current case does go further in the court system here (as it is possible to imagine it might given the finely balanced nature of the judgments, and the absence of prior binding authority), it is to be hoped that the question may at least be asked as to whether it is right to expand the range of circumstances in which English law identifies that that a person with cognitive impairments is not to be seen as seen as responsible for their own actions, and hence, arguably, to move the UK further from, rather than closer to, CRPD compliance.

[1] Using Latin terms which should no longer be in use, the defence is often described as depending on “the ex turpi causa principle” (or “rule”), referring to the maxim ex turpi causa non oritur actio.

[2] The jury sent a note to the judge during the trial in the following terms: “We the Jury have been concerned at the state of psychiatric health service provision in our county of Devon. Can we be reassured that the failings in care for [the Claimant] will be appropriately addressed following this trial.”

[3] See, for instance, the part that it played in shaping the thinking of the independent Review of the Mental Health Act 1983.

[4] For those unfamiliar with this, this reading list may be useful: Legal and mental capacity – a reading list – Mental Capacity Law and Policy.

[5] See for a nuanced discussion of the CRPD and criminal law, Jill Craigie, Against a singular understanding of legal capacity: Criminal responsibility and the Convention on the Rights of Persons with DisabilitiesInternational Journal of Law and Psychiatry40, 6-14.

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