In circumstances where a person with mental illness has injured another, compensation is sometimes sought from medical practitioners for not detaining the mentally ill person. Presland and McKenna are well known examples.
Less commonly seen are claims seeking compensation from the mentally ill person, framed in such a way as to permit recovery from an insurer, such as under a house & contents insurance policy with cover for accidentally causing bodily injury. Stephen Warne recently drew attention to such a case, addressed at an appellate level in England in mid 2015.
Dunnage v Randall & UK Insurance Limited  EWCA Civ 673 arose from a visit by the claimant to his uncle at the uncle’s home. Suffering paranoid schizophrenia, the uncle set himself alight and in attempting to prevent that the claimant suffered burns. The uncle died and the claim was made in negligence (at )) against the estate and ultimately the insurer.
The Court of Appeal noted that the uncle owed a duty of care (at ), presumably as occupier. “The issue is simply whether, unwell as he was, he breached that duty since he did not measure up to the objective standard of care.”
Explained further by Lady Justice Arden, the issue was whether the uncle’s conduct was involuntary for the purposes of the legal rule excluding negligence liability for involuntary conduct: .
Perhaps the best summary appears in the reasons of Lord Justice Vos at  – :
In my judgment, only defendants whose attack or medical incapacity has the effect of entirely eliminating any fault or responsibility for the injury can be excused. It is only defendants in that category that have not actually broken their undoubted duty of care. The actions of a defendant, who is merely impaired by medical problems, whether physical or mental, cannot escape liability if he causes injury by failing to exercise reasonable care.
What then does it mean to say that a medical condition entirely eliminates any fault or responsibility for the injury? It simply means that the defendant himself did nothing to cause the injury. Mr Michael Davie QC, leading counsel for the first defendant, gave the example of a person whose arm is holding a knife and who is overcome by another forcing him to stab a victim. The person holding the knife cannot have broken his duty of care because he did nothing himself.
In my judgment, however, at all intermediate stages where the defendant does something himself he risks being liable for failing to meet the standards of the reasonable man. This approach avoids the need for medical witnesses to become engaged with difficult and undefined terms such as volition, will, free choice, consciousness, personal autonomy and the like. It is only if the defendant can properly be said to have done nothing himself to cause the injury that he escapes liability. This approach is not directly adopted in any of the authorities, but reflects in large measure, I think, the conceptual analysis favoured by at least 3 of the justices in Corr v. IBC Vehicles Limited  1 A.C. 884 per Lord Scott at paragraph 31, per Lord Mance at paragraphs 51-2, and per Lord Neuberger at paragraph 65 (who put the matter in terms of asking whether the deceased had “no real “fault” for his suicide”).
This approach also has the attraction of not requiring any fine distinction to be made between the effects of physical health problems and mental health problems. Such a distinction seems to me, in the light of modern science, to be outdated and inappropriate. Even mental health problems often have some physical cause or manifestation. There is neither a logical nor a societal reason why the law should differentiate in this area between the two
Although the uncle’s conduct was not involuntary, was the claimant’s injury accidental? That required consideration of the facts and the medical evidence. Lady Justice Arden briefly stated at :
The critical matter is whether the injury suffered by the claimant was accidental bodily injury. In my judgment, the injury was accidental because on the evidence Vince had clearly lost control of his ability to make choices and therefore he could not be said to have intended to cause injury to the claimant (see the cases already cited, and see per Lord Clarke of the Outer House of the Court of Session in Howie v CGU Insurance plc  CSOH 110 at ). I accept Mr Spearman’s submission that it would be unrealistic to interpret accidental injury or damage in the policy as limited to that caused by some means external to the insured: that would reduce the cover to significantly less than the parties must have contemplated. It is in any event not shown how the lighter ignited the petrol. It may have gone off accidently in the course of the fight that took place on the floor.
It is noteworthy that the claim was made in negligence. Lady Justice Arden commented at :
The position is different if a specific mental state is required, as in the case of intentional torts. In those circumstances it is necessary to take into account a person’s special characteristics…