The second half of the 20th century witnessed a number of serious miscarriages of justice that resulted from improper police interviewing of suspects and unreliable and false confessions. To prevent miscarriages of justice involving people with mental disorder or particular mental vulnerabilities, psychiatrists have a role in determining the fitness to be interviewed of persons suspected of criminal offences. In this article, the role of the psychiatrist in assessing fitness to be interviewed is set against the background of the latest revisions of the Codes of Practice of the Police and Criminal Evidence Act 1984 and relevant case law in England and Wales.