Have you ever watched a crime and thought of "having a go" and arresting the thief. The law says that you have the power to make such an arrest, but only if an arrestable offence is actually being committed. Apart from a bloody nose, you might also end up being expensively sued, and sometimes prosecuted, for assault, wrongful arrest or false imprisonment.

In 1991, a police officer was seen leaving a shop with a chocolate bar which he had apparently not paid for. The store detective, and a sales assistant, followed. A scuffle ensued and he ran off. A passer-by ran after him and made a citizen's arrest for shop-lifting. In the process, he in turn was kicked by the off-duty officer.

Later, the defendant was acquitted of theft, but found guilty on two counts of assault with intent to resist arrest. He appealed, saying that the arrest was unlawful. He was, again, successful. Once acquitted of the theft, the arrest has become, retrospectively, unlawful. Presumably, it would therefore be open to the former defendant to bring an action for wrongful arrest.

It is different for a policeman making an arrest. The police officer need only have reasonable grounds for suspecting there has been an arrestable offence.

Unlawful Arrest

One case of unlawful arrest by a police officer did lead to a civil action for damages. The background was unusual. The person arrested conceded that the arresting officer had reasonable grounds for suspecting that an arrestable offence (of assault) had been committed, and that the person arrested was guilty. Following arrest the suspect was detained at the police station for four hours and then released without charge.

The point at issue was that the complaint had been withdrawn. There was also evidence that the arresting officer was aware of this and there was, therefore, no possibility of a charge being brought. If the officer had had no idea whether a charge would be brought, the arrest would have been lawful. But when he knew personally that this was not a possibility, he had acted on some irrelevant consideration, or for improper purpose. In the circumstances the Court Of Appeal held that the claim for damages could proceed.

Being a responsible citizen can also be expensive.