Preliminary examination of an insanity defense typology: Prevalence rates and correlates

The present investigation was designed to systematically examine the insanity defense typology proposed by Brown (2018) using a large sample of cases wherein there was support for the insanity defense. A total of 187 court-ordered cases in which an insanity defense was supported were categorized based on the typology. The sample comprised of mostly single, middle-aged males who had been charged with a felony and diagnosed with a psychotic disorder. About half the sample was ultimately adjudicated not guilty by reason of insanity by the court. About two-thirds of the cases were categorized into one of the seven insanity defense subtypes using a coding scheme developed by the author of the typology. Inter-rater agreement occurred 82% of the time. The most frequent subtype was Paranoid Self-Defense, followed by "But It's Mine" and Paranoid Protection of Others. There were few differences among these subtypes based on demographic, clinical, offense, and outcome variables, except for presence of a primary psychotic disorder and offense type. Implications and ideas for future research are discussed.