Psychological autopsies are often conducted after completed suicides, and entails interviewing relatives as well as reviewing clinical records. The aim is to produce a full view of mental and physical health, personality social adversity, leading up to the suicide to understand why the person killed themselves.
One issue is that this methodology often overestimates the rate of psychiatric diagnoses in suicides. Psychological autopsy studies estimate the rate of psychiatric disorders in suicides to be around 90%, but epidemiological data (cited by Craig Bryan in Rethinking Suicide) finds that about 45-50% of those who die by suicide have a diagnosis of a mental disorder in registries.