Perjury is the deliberate concealment of facts or conscious distortion of the truth by a witness or victim, either during a preliminary investigation or in court. Perjury could result in the conviction of an innocent person, or the acquittal of a criminal, thereby rendering court decisions vulnerable.
Investigations of corruption in police forces frequently note incidences of policy officers perjuring themselves. In 1993 a leading Scottish judge accused police officers of this.