On July 20, 2012, a man reportedly walked into a theater in a Denver suburb and opened fire on the audience. In the course of a few minutes, he killed 12 people and injured 70. During his murder trial, his attorneys have admitted that he committed the shooting. However, as in North Carolina, Colorado law allows someone charged with a crime to potentially escape capital punishment by pleading not guilty by reason of insanity.
Not all states allow an insanity defense. According to the National Institute of Mental Health, about 90 percent of the defendants who raise the insanity defense do suffer from some form of mental illness. However, the defense works in only one out of four cases in which it is tried.
Part of the explanation lies in the difference between being mentally ill and being insane. Many people, in prison and out, suffer from mentally illness, yet a much smaller number are insane. The M’Naghten test is most commonly used to determine insanity. The question the jury must answer is whether the defendant knew right from wrong at the time he or she committed the act.
Although used rarely, the insanity defense does work sometimes. For the man in this case, the jury’s decision regarding his mental state at the time of the shootings could be the difference between capital punishment and life in prison. Because the insanity defense presumes that the defendant actually committed the act, a criminal defense attorney will likely consider whether or not to use the defense very carefully.