Negligence claim against NHS Trust barred by illegality defence

United Kingdom

In a unanimous decision, the Supreme Court has held that the illegality defence barred a claimant convicted of manslaughter from claiming damages for losses she suffered as a result of an earlier criminal conviction. The Court confirmed that the correct approach to the illegality defence is a flexible one that involves a high-level review of purpose, public policy and proportionality.


Ms. Henderson suffered from paranoid schizophrenia and was being treated by the mental health team managed by the Dorset Healthcare University NHS Foundation Trust. During a psychotic episode, Ms. Henderson stabbed her mother to death and was subsequently convicted of manslaughter by reason of diminished responsibility. At the criminal trial, the judge remarked that Ms. Henderson did not bear a significant degree of responsibility for her actions and made a hospital order and an unlimited restriction order under the Mental Health Act 1983.

Ms. Henderson brought a claim against Dorset Healthcare Trust for negligently failing to provide proper care when her psychiatric condition deteriorated, causing the psychotic episode which resulted in the stabbing of her mother. She sought to recover:

  • damages for the depressive disorder and post-traumatic stress disorder;

  • damages for loss of liberty;

  • loss of amenity;

  • the share in her mother’s estate which she did not inherit due to operation of the Forfeiture Act 1982;

  • the cost of psychotherapy; and

  • the cost of a care manager/support worker.

Dorset Healthcare Trust admitted liability in negligence in failing to return Ms. Henderson to the hospital when her psychiatric condition worsened and admitted that if it had done so, Ms. Henderson’s mother would not have been killed. However, Dorset Healthcare Trust argued that the damages sought by Ms. Henderson were irrecoverable because they arose out of the sentence imposed on her by the Criminal Court (and the criminal act of manslaughter) and were therefore barred by the illegality defence.

Consequently, the recoverability of the damages was tried as a preliminary issue.

High Court Decision and Court of Appeal Decision

In the High Court, Jay J found in favour of the Dorset Healthcare Trust holding that he was bound by the existing decision in Clunis v Camden and Islington Health [1998] QB 978 and the House of Lords’ decision in Gray v Thames Trains Ltd [2009] UKHL 33. He considered that the facts in both Gray and Clunis were materially identical to the current case and that the illegality defence applied even if the claimant did not bear significant responsibility for her actions.

The Court of Appeal agreed with the High Court’s decision and dismissed Ms. Henderson’s appeal.

Supreme Court Decision

The Supreme Court decision turned on whether Ms. Henderson’s case could be distinguished from Gray and if not, whether the Court should depart from Gray in light of the more recent decision in Patel v Mirza [2016] UKSC 42.

The Supreme Court dismissed Ms. Henderson’s appeal holding that:

  • Ms. Henderson’s claim could not be distinguished from Gray on the grounds that she did not bear significant responsibility for her criminal act. The crucial consideration in Gray was that the claimant had been found criminally responsible for his actions – the degree of personal responsibility was not the decisive factor.

  • The correct approach to the illegality defence included a balancing of public policy considerations as per the three stage test deployed in Patel v Mirza, and that the underlying policy question was whether allowing recovery would cause inconsistency in the law thereby damaging the integrity of the legal system. In this respect, the three key considerations were: (a) the underlying purpose of the illegality and whether that purpose would be enhanced by denying the claim; (b) any other aspect of relevant public policy on which denying the claim may have an impact; and (c) whether denying the claim would be a proportionate response to the illegality.

  • A claimant should not be allowed to recover damages for loss resulting from the sentence imposed by the criminal court and/or an intentional criminal act for which the claimant is held to be responsible. Such an approach would create inconsistency between the civil and criminal law, thereby damaging the integrity of the legal system. This was because the criminal (as classified under the criminal law) would become the ‘victim’ under the civil law and it would be inappropriate for the civil courts to decide on the degree of personal responsibility of the claimant for their own criminal act(s).

  • The illegality defence would not necessarily be engaged in the case of trivial or strict liability offences, but the offence of manslaughter by diminished responsibility was a serious offence that would attract the defence.

The Court found that the following public policy reasons weighed in favour of denying Ms. Henderson’s claim:

  • the gravity of Ms. Henderson’s offence;

  • the public interest in the proper allocation of NHS resources;

  • the close link between the damages claimed and her offence; and

  • the public interest in preventing unlawful killing – although the prospect of not recovering civil damages would not deter a claimant in Ms. Henderson’s position from committing manslaughter, a clear rule against profiting from killing could have a deterrent effect.


The decision reaffirms that healthcare organisations can use the illegality defence in circumstances where it is alleged that the organisation’s failings led to subsequent criminal acts. That rule is however not absolute and will depend upon the specific facts and the extent to which public policy considerations are applicable when considering whether or not to use such a defence.