3. Illegality
In some cases, a defendant may argue that the plaintiff’s claim should fail because it is founded on, or is too closely connected with, the plaintiff’s own illegal conduct. This is known as the defence of illegality or ex turpi causa. It is a complete defence, and the burden of proving it rests on the defendant.
The traditional maxim is ex turpi causa non oritur actio: no action arises out of illegal or immoral considerations.
The defence is exceptional and depends heavily on context. The court does not apply it automatically whenever unlawful conduct is present. If the illegality is trivial, incidental, or merely part of the background, the claim may still succeed. Instead, it considers whether denying the claim would be a proportionate and principled response having regard to the relationship between the illegality and the injury claimed.
Relevant considerations include:
- the purpose of the law that has been broken, and whether denying the claim would further that purpose;
- any other relevant public policies, including policies that may support allowing the claim; and
- whether denial of the claim would be a proportionate response to the illegality.
For example, if two people jointly engage in dangerous unlawful conduct and one is injured in the course of it, the court may have to consider whether public policy should bar or limit recovery. But where the plaintiff’s unlawful act is only incidental, or where ordinary principles such as contributory negligence adequately address the case, the defence may not apply.
In assessing proportionality and coherence, the court may also consider factors such as:
- whether allowing the claim would undermine the integrity of the legal system;
- whether there is a sufficient causal connection between the illegality and the damage claimed;
- whether the plaintiff must rely on the illegality to make out the claim;
- the seriousness of the illegal conduct; and
- the relative culpability of the parties.
The defence is more likely to succeed where:
- the loss claimed is the direct consequence of the plaintiff’s own criminal conduct;
- allowing recovery would enable the plaintiff to profit from wrongdoing or evade a criminal penalty; or
- the claim is so closely connected with the illegality that allowing it would damage the coherence or integrity of the law.
In one case, the defendant’s negligence caused the plaintiff to suffer post-traumatic stress disorder. While affected by that condition, he killed another person and was convicted of manslaughter. He then claimed damages for loss of earnings after his arrest and for damage flowing from his detention and conviction. Those claims were barred. The court held that a person cannot recover for loss flowing from a lawful sentence imposed for his own criminal act.
By contrast, the defence may fail where:
- the plaintiff’s unlawful conduct was only incidental;
- the injury was caused directly by the defendant’s negligence, rather than by the plaintiff’s criminal act;
- stronger public policy considerations support allowing the claim; or
- the plaintiff belongs to a class of persons whom the law is designed to protect.
In one case, the plaintiff was engaged in illegal hawking when he was injured by the collapse of the defendant’s concrete balcony. The court allowed his claim. His illegal hawking did not prevent recovery for the personal injuries caused by the defendant’s negligence because illegality was only incidental.
