• In the case of Henderson v Dorset University NHS Trust [2018] E.W.C.A. Civ 1841, it was held that although an NHS trust had provided negligent care of a paranoid schizophrenic patient which led to her conviction of manslaughter for killing her mother during a psychotic episode, the court was bound by Clunis v Camden & Islington HA [1998] Q.B. 978, and Gray v Thames Trains Ltd [2009] UKHL 33 bar the patient’s damages claims on the doctrine of illegality.

Facts of the Case

  • C had been diagnosed at different times as suffering from paranoid schizophrenia.
  • From about 2003, she had various formal admissions under the Mental Health Act 1983 and informal hospital admissions.
  • On 25 August 2010, whilst experiencing a serious psychotic episode, C stabbed her mother to death.
  • At the time of the offence, C was under the care of a community mental health team managed and operated by D.
  • An independent investigation found failings by D in C’s care and treatment. It concluded that, while the killing of C’s mother could not have been predicted, a ‘serious untoward incident of some kind’ was foreseeable based upon C’s previous behaviour when experiencing a psychotic episode.
  • Thus, the killing was preventable and, had a rapid response been forthcoming, the tragic incident would probably not have occurred.
  • Therefore, the event would not have happened but for D’s breaches of duty in failing to respond appropriately to C’s mental collapse.
  • C was convicted of manslaughter by reason of diminished responsibility. C had been subject to detention under the 1983 Act ever since.


  • Did precedent prevent D from raising the defence that C could not claim damages stemming from her own illegal act?

Held by the Court of Appeal (Civil Division)

  • Finding for D, that the authorities outlined that a person convicted of a serious criminal offence could not recover damage in tort which was a consequence of their criminal act, or the subsequent detention imposed on them. As a matter of public policy, the defence of illegality applied to C because she had been convicted of manslaughter.

Sir Terence Etherton MR, Sir Ernest Ryder SPT and Lady Justice Macur

  • The Clunis case had been approved by the House of Lords in subsequent cases. Lord Hoffmann restricted the ratio of Clunis into two authorities.
  • First, that a person convicted of a serious criminal offence cannot recover damage in tort resulting from a sentence of detention imposed upon them for the criminal act.
  • Second, that such a person cannot recover for damage which is the consequence of their criminal act.
  • As a matter of public policy, there is a defence of illegality to all C’s claims for damages. C has been convicted of a serious criminal offence. C’s mental state did not justify a finding of not guilty by insanity, so C cannot be said to not know what she was doing or that it was wrong. The court cannot question the conviction to ascertain that she had no responsibility. C is relying on her illegal act of manslaughter to advance her claims, and so they must fail.
  • “Furthermore, as is set out above, it is clear that the members of the appellate committee in Gray had considered issues which might undermine the application of the rule of public policy applicable in situations such as that in Gray, Clunis and the present case. They considered the situation where the mental illness of a claimant in tort proceedings against a health authority meant that, despite the conviction for manslaughter which predicates that the claimant committed the offence with intent to kill or to cause grievous bodily harm, they bore no or insignificant responsibility for the killing. As stated above, Lords Hoffmann, Roger and Scott were of the view that the claim against the health authority should, nevertheless, be barred on grounds of public policy…For those reasons, Gray remains binding on us and so does Clunis” [89].