"Curiously, during the period before deinstitutionalization, the mentally ill seem to have been less likely to be arrested for serious crimes than the general population."

"Studies in New York and Connecticut from the 1920s through the 1940s showed a much lower arrest rate for the mentally ill. In an era when involuntary commitment was relatively easy, those who were considered a danger to themselves or others would be hospitalized at the first signs of serious mental illness. The connection between insanity and crime was apparent, and the society took a precautionary approach. Mentally ill persons who were not hospitalized were those not considered a danger to others. This changed as deinstitutionalization took effect."

From "Madness, Deinstitutionalization & Murder," by Clayton Cramer.