Court case[1895] 1 QB 918

Sherras, a licensed publican, served liquor to a police constable who was on duty but had taken off his armlet, the usual sign that a constable was on duty. Section 16(2) of the Licensing Act 1872 punished a licensee who supplied liquor to a constable on duty, and said nothing about knowledge. The publican honestly believed the constable was off duty. The magistrates convicted him.

The Queen's Bench Division quashed the conviction. Wright J held that there is a presumption that mens rea, an evil intention or knowledge of the wrongfulness of the act, is an essential ingredient of every offence; the presumption may be displaced by the words of the statute or by its subject matter, but here nothing displaced it. He identified three classes of statutory offence where the presumption is displaced: acts which are not criminal in any real sense but are prohibited under a penalty in the public interest (such as adulterated food), public nuisances, and proceedings which are criminal in form but are really a summary way of enforcing a civil right.