The authors examined the cohort of all defendants pleading not guilty by reason of insanity over a 12-month period in Baltimore City's superior trial court. During that time, 143 of the 11,497 defendants indicted (1.2%) pled not criminally responsible. Fourteen of those defendants (10%) were subsequently found not guilty by reason of insanity. The authors found marked agreement between the prosecution and defense with only two cases leading to full trials where the issue of insanity was argued. The evaluating physician's opinion as to criminal responsibility and Axis I diagnosis, and the most serious underlying charge discriminated between those defendants found not guilty by reason of insanity and those defendants found guilty or not guilty by the court. Other demographic factors such as age, number of dependents, educational level, severity of illness, and criminal background did not discriminate between the two groups.