High-profile murder trials with defendants who invokes insanity defenses may lead some Texas court watchers to believe that such a defense is a common occurrence in criminal cases. In actuality, a defense of not guilty by reason of insanity is asserted in only 1 percent of county court cases, according to the National Institute of Mental Health, and when asserted, fails at a far greater rate than it succeeds.
The low success rate of insanity defenses may be borne of the inability of the general population from which juries are assembled to understand the centuries-old and controversial concept. However, that a person who commits a violent crime is likely to be mentally ill is a fact supported by the Bureau of Justice Statistics, which found that over 60 percent of inmates have some degree of mental illness, with 20 percent of those being seriously mentally ill and 15 percent of state prison inmates having psychotic disorders.
Within months of each other, the defendants in the “American Sniper” case, the Aurora theater mass killings, and the case of a young woman killed by a mentally ill man in Boston, all have claimed insanity as a defense. That they committed the crimes of which they were accused was not the question at trial. Instead, the issue was whether at the time of committing the crimes, they knew what they were doing was wrong.
A murder defendant who is found not guilty by reason of insanity will likely end up being committed to a facility until determined to no longer be a threat to society. A criminal defense attorney might consider this as a strategy, especially in states where a conviction could result in the imposition of the death penalty.