Henderson v Dorset Healthcare University NHS Foundation Trust – Case Summary

Henderson v Dorset Healthcare University NHS Foundation Trust

Supreme Court

Citations: [2020] UKSC 43.


The appellant suffered paranoid schizophrenia. The respondent, an NHS Foundation Trust, was responsible for her care. Due to their negligence, the appellant was not admitted to hospital when it became apparent that she was having a serious psychotic episode. During this episode, she stabbed her mother to death.

The appellant was subsequently convicted of voluntary manslaughter by reason of diminished responsibility. This resulted in her being sentenced to a hospital order under the Mental Health Act 1983. The appellant sued the respondent in negligence. She claimed the following losses:

  • Damages for the loss of amenity, depressive disorder and PTSD she suffered as a result of killing her mother;
  • Damages for the loss of liberty imposed by her sentence;
  • Damages to reflect her inability to inherit under her mother’s estate due to the provisions of the Forfeiture Act 1982.
  • Future losses, including the cost of psychotherapy and a care worker.

The respondent argued that the defence of illegality barred the appellant’s claim.


The claim in this case raised the issue of whether Gray v Thames Trains Ltd [2009] UKHL 33 remained good law in light of the Supreme Court’s reform of the defence of illegality in Patel v Mirza [2016] 3 WLR 399.  In Gray, Lord Hoffman stated that there were two illegality rules in tort:

  • The narrow rule: a claimant cannot recover in tort for the consequences of a criminal sanction – such as the cost of a fine or the loss of liberty.
  • The wide rule: a claimant cannot recover for losses which were caused by their own illegal actions (other than those caused by a criminal sanction) – such as remorse or the risk of being sued by the victim.

Lord Hoffman argued that these rules did not arise from the defence of illegality. Rather, they are the normal application of novus actus interveniens principles in causation. If this is true, then the ruling in Patel v Mirza might not affect this area of tort. The lack of causation precludes liability, making defences irrelevant.

However, Lords Brown and Roger in Gray disagreed that the rules in tort were based on causation. They attributed the rules to the defence of illegality. If this is true, then the two rules in Gray have been replaced by the approach in Patel v Mirza. Even so, how Patel v Mirza might apply in this kind of case was unclear. This was particularly true in light of Lord Phillip’s obiter dicta in Gray speculating that the rules might not apply where the criminal sentence did not indicate that the offender was personally responsible for the offence (particularly where the sole sentence was a hospital order).

These were the issues the Supreme Court was asked to decide in this case.


The Supreme Court held in favour of the respondent.

  • They held that all of the appellant’s losses were barred by the defence of illegality. Since the facts were materially the same as the facts in Gray, the case could not be distinguished and should have the same outcome.
  • The court declined to adopt the obiter dicta of Lord Phillips in Gray. The court thought that introducing such an exception would create conflict between the civil and criminal law.
  • The correct approach to apply in any civil case is the defence of illegality as defined in Patel v Mirza.
  • The reasoning in Gray was compatible with the principles in Patel. The judges had correctly identified the strong policy considerations in favour of the wide and narrow rules – particularly the need to maintain consistency between the criminal and civil law.
  • Applying the ‘trio of considerations’ approach in Patel to the present facts, the defence of illegality barred the claim. In addition to the policy factors identified in Gray, the court was influenced by the following: the gravity of the offence; the value of deterring and condemning such offences; the close connection between the offence and the claim; the public interest in the proper allocation of NHS resources; and the fundamental value of the right to life.
This Case is Authority For…

The court provided the following guidance on applying the ‘trio of considerations’ test in Patel v Mirza:

  • Where policy considerations under the first two stages of the test come down firmly in favour of the defence applying, there is not usually any need to consider the third stage;
  • Considerable weight should be given to the policy that a person should not benefit from their own wrongdoing;
  • Considerable weight should be given to the need to maintain consistency between different areas of law;
  • When considering whether denying the claim would be proportionate, the centrality and closeness of the causal link between the illegality and the claim is an important factor.

The approach to the defence of illegality outlined in Patel v Mirza is based on principles which existed in the prior case-law. As such, the prior case-law remains relevant unless it is incompatible with the reasoning in Patel.


Notably, while the Supreme Court approved of the outcome and policy-based reasoning of Gray, they did not endorse treating the issues in this kind of case as a matter of causation. Since causation is analytically prior to defences, this hints that criminal acts do not necessarily break the chain of causation.

However, the Supreme Court did not expressly disapprove of the causation approach. It may be the case that the causation approach could not apply in this case. This is because the appellant was not acting independently of the respondent’s negligence. Her judgement was impaired by her mental illness, which the respondent was supposed to manage. It is therefore possible that an criminal act independent of the defendant’s negligence would normally break causation.

The court suggested that there may be some very trivial or strict liability offences which will not trigger the illegality defence. A serious offence like manslaughter, by contrast, generally will.