Insanity defense pleas in Baltimore City: an analysis of outcome

The authors studied all defendants in Baltimore City's circuit and district courts who pleaded not criminally responsible, Maryland's version of the not guilty by reason of insanity plea, during a 1-year period. The study was designed to compare the perception that the insanity plea is misused to actual outcome data.

The cohort of defendants who pleaded not criminally responsible in both the circuit and district courts during calendar year 1991 was identified. Data on demographic characteristics, crimes committed, diagnoses, and psychiatrists' opinions on criminal responsibility were collected. Trial outcome data were obtained through a search of the circuit and district court computer systems.

Of the 60,432 indictments filed in the two courts, 190 defendants (0.31 per 100 indictments) entered a plea of not criminally responsible. All but eight defendants (0.013 per 100 indictments) dropped this plea before trial. For these eight cases, both the state and the defense agreed that the defendant should be found not criminally responsible, and the plea was uncontested at trial. The remaining defendants had their charges dropped before trial, remained not competent to stand trial at the time of the study, or withdrew their pleas of not criminally responsible before trial.

There were no trials that contested the plea of not criminally responsible. The state and defense agreed with each other for all of the defendants who actually retained the plea at trial. The perception that the insanity defense is overused and misused is not borne out by data.