The Defence of Illegality in a clinical negligence context: consideration of Ecila Henderson (A Protected Party, by her litigation friend, the Official Solicitor) (Appellant) v Dorset Healthcare University NHS Foundation Trust (Respondent) [2020] UKSC 43



Where a Claimant, during a serious psychotic episode, committed a criminal offence, which she would not have committed but for the Defendant’s negligence, can she recover damages for the consequences of having committed the offence, including her subsequent loss of liberty?

That was the question before the Supreme Court in Ecila Henderson (A Protected Party, by her litigation friend, the Official Solicitor) (Appellant) v Dorset Healthcare University NHS Foundation Trust (Respondent) [2020] UKSC 43.

Whilst, perhaps unsurprisingly, the Supreme Court found that such a claim was barred by the defence of illegality, the judgment is a useful reminder of the key principles to be considered when such issues emerge.

The Facts

The Claimant suffers from paranoid schizophrenia or schizoaffective disorder. In August 2010, she was under the care of Southbourne community mental health team, which was managed and operated by Dorset Healthcare. Her condition deteriorated that month, and on 25th August 2010 she stabbed her mother to death whilst experiencing a serious psychotic episode.

The Claimant was convicted of manslaughter by reason of diminished responsibility. The Judge, during her criminal trial, stated that the Claimant should not be seen as bearing a significant degree of responsibility by reason of her psychiatric condition. She was sentenced to a hospital order under section 37 of the Mental Health Act 1983. She remains in hospital and is not expected to be released for some time.

The Claim

The Defendant accepted that they were negligent in their failure to return the Claimant to hospital when her psychiatric condition deteriorated and accepted that had they done so within a reasonable timeframe, the killing would not have occurred.

The leading case considering such issues was Gray v Thames Trains Ltd [2009] UKHL 33 which found that the damages were irrecoverable which found that the civil claim was barred for illegality because the damages sought result from the sentence imposed by a criminal court and a criminal act. This issue, in the claim before the court, was listed as a preliminary issue. The High Court and Court of Appeal had found for the Defendant. The Supreme Court considered whether the case could be distinguished from Gray and if not whether they should depart from Gray, particularly in the light of Patel v Mirza [2017] AC 467, a commercial case concerning the scope of illegality.

The Supreme Court unanimously dismissed the appeal. The claim was barred for the very same reasons as Gray. The Claimant argued that the matter before the court could be distinguished as she did not have ‘significant personal responsibility’ for the crime, and thus the defence of illegality could be overcome. The court disagreed: the crucial consideration in Gray is that the Claimant had been found to be criminally responsible for their conduct and the degree of personal responsibility was largely irrelevant. The facts could not be distinguished.

The court was then invited to depart from Gray. The proper approach to the illegality defence at common law was one based on a balancing of public policy considerations rather than a reliance-based approach (Patel). In this case, the court found that the underlying policy question to be whether allowing recovery for something which is illegal would produce inconsistency and disharmony in the law and so cause damage to the integrity of the legal system. In assessing whether the public interest would be harmed in that way, the court should consider a “trio of considerations”, namely:

  • stage (a) the underlying purpose of the illegality in question, and whether that purpose would be enhanced by denying the claim;
  • stage (b) any other relevant public policy on which denying the claim may have an impact;
  • and stage (c) whether denying the claim would be a proportionate response to the illegality.


The court confirmed that the decision provided a guidance on the proper approach to the common law illegality defence across civil law generally.

The court offered useful reasoning as to the strong public policy considerations to protect the defence of illegality in such claims. The court rejected the relevance of personal responsibility, stating that to do so would lead to absurdities – the criminal under criminal law would become the victim under civil law. Requiring the civil court to assess whether or not a civil Claimant has a significant degree of personal responsibility for their crime would create a clear risk of inconsistent decisions being reached in the criminal and civil courts. Further, the court was unclear why ‘significant personal responsibility’ is the appropriate threshold and the role of the civil courts in assessing such a threshold. The court did muse that there may be some ‘exceptional’ trivial or strict liability offences which do not engage the illegality defence. It should also be reminded to litigators that the damages flowed directly from the result of the criminal act and a sentencing from criminal proceedings. Other heads of loss may stand more chance of success. In this case, however, the court also found it would be inappropriate for the court to subvert the operation of the Forfeiture Act 1982, which prevented the Claimant from recovering her full share of her mother’s estate.

The case is a useful example of the strict rules governing the illegality defence. Even where causation from the negligent act to the consequences of a criminal act is clear, without any arguable novus actus interveniens, public policy considerations will be paramount.

The full judgment can be read here.

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