Suicide may be defined as intentional self-killing, although the definition has been the subject of critical review (Fairbairn, 1995). As the determination of whether intent was present at the time of death by suicide can be difficult, coroner's inquests tend to underestimate the number of suicides. At the time of suicide, the vast majority of people are suffering from some form of mental disorder, although there may, exceptionally, be a few rational suicides. Suicide is a relatively uncommon event, but the possibility of suicide by those with mental disorders is always a potential hazard faced by health and allied professionals responsible for their care. Detention of a patient in hospital under mental health legislation is often precipitated by concern regarding risk of self-harm and/or risk of harm to others and potential for absconding and, at times, admission to a locked or secure facility is necessary. Detained patients in secure facilities include both offender patients, admitted through the courts or transferred during sentence from prison, and patients on civil orders under sections 2 or 3 of the Mental Health Act 1983. The relationship between suicidal behaviour and that which is violent or homicidal is complex but relevant to an understanding of the phenomenon of suicide in secure conditions.