Illinois residents may be aware that a defense based on insanity is being mounted by attorneys representing the man accused of killing 12 people in a Colorado movie theater in July 2012. While many people may believe that this kind of behavior demonstrates clear evidence of some form of mental defect, this type of defense is actually quite rare. Attorneys representing defendants may be reluctant to enter a plea of not guilty by reason of insanity for a number of reasons.

One of the chief disadvantages of this kind of criminal defense is the sanctions that are associated with it. When successful, the defendant will be placed in a mental care facility until it can be demonstrated that he or she is no longer a threat to society. This could effectively mean confinement for life, and this is why the insanity defense is often reserved for death penalty cases like the Colorado movie theater shootings.

Unsympathetic juries are another reason why an insanity defense is rarely brought up. This strategy is often associated with heinous crimes, and juries may view a claim of insanity as a legal trick. Statistics from the National Institute of Mental Health reveal that an insanity defense is only raised in about 1 percent of criminal county court cases, and the strategy is only successful about a quarter of the time.

Experienced criminal defense attorneys may be familiar with the challenges involved in mounting a criminal defense based on insanity, and they will likely exhaust other available options before taking this path. An attorney may seek to have charges reduced or dismissed before trial by challenging the validity of the evidence, questioning the behavior of police officers or negotiating a plea agreement with prosecutors.