For a court to find a person guilty of an offence, sufficient evidence must be presented to satisfy the court beyond reasonable doubt that the suspect is guilty of the offence. It is almost always the police who obtain that evidence.

When investigating a crime, the police may question anyone. It is a fundamental principle of the criminal law that a person may refuse to answer all questions put to him or her. There are, however, a number of exceptions to this rule requiring that a person answer certain questions in some cases, whether they are a suspect or not.

It is advisable to co-operate with the police and be polite, answering those questions which must be answered, but to refrain from answering any other questions. If there is anything a suspect wants to tell the police, such as an 'air tight alibi', they should see a lawyer so that the lawyer can help to give the information to the police. It is advisable to give that information to police as soon as possible so that it does not later look like a case of inventing an alibi. Before answering any questions a person should seek immediate legal advice, however one must supply information in the following situations.