Folie à deux and homicide: Literature review and study of a complex clinical case

Folie à deux is a psychiatric illness involved in homicides.

To study the mechanisms leading to homicide and determine homicide risk factors in folie à deux patients through a literature review and the study of a complex clinical case.

We included articles available on PubMed, ScienceDirect or Cairn that address the forensic implications of folie à deux. Then, we analyzed the criminal psychiatric assessments of two murderers (husband and wife) of a child in a case of folie à deux.

Seventeen articles were included. In the cases examined, homicides were committed with great violence, usually against a victim in the family circle, and were sometimes followed by suicide. The main risk factor for homicide was the combination of mystical and persecutory delusions. The homicides occurred in response to destabilization of the delusional dyads. Concerning the clinical case, we described the circumstances surrounding the killing and analyzed the four expert reports that permit us to infer the occurrence of induced psychosis, which is a form of folie à deux.

Psychiatrists must attain a better knowledge of folie à deux to allow early identification of risk situations and to improve their assessments.