The Defendant Did It, But ...

Sometimes a defendant can avoid punishment even if the prosecutor shows that the defendant did, without a doubt, commit the act in question.

Self-Defense

Self-defense is a defense commonly asserted by someone charged with a crime of violence, such as battery (striking someone), assault with a deadly weapon, or murder. The defendant admits that she did in fact commit the crime, but claims that it was justified by the other person's threatening actions. The core issues in most self-defense cases are:

• Who was the aggressor?
• Was the defendant's belief that self-defense was necessary a reasonable one?
• If so, was the force used by the defendant also reasonable?

The Insanity Defense

The insanity defense is based on the principle that punishment is justified only if the defendant is capable of controlling his or her behavior and understanding that what he or she has done is wrong. Because some people suffering from a mental disorder are not capable of knowing or choosing right from wrong, the insanity defense prevents them from being criminally punished.

The insanity defense is an extremely complex topic; many scholarly works are devoted entirely to explaining its nuances. Here are some major points of interest:

• Despite popular perceptions to the contrary, defendants rarely enter pleas of "not guilty by reason of insanity." When they do, judges and jurors rarely uphold it.

• Various definitions of insanity are in use because neither the legal system nor psychiatrists can agree on a single meaning of insanity in the criminal law context. The most popular definition is the "McNaghten rule," which defines insanity as "the inability to distinguish right from wrong." Another common test is known as "irresistible impulse": a person may know that an act is wrong, but because of mental illness he cannot control his actions (he's described as acting out of an "irresistible impulse").

• Defendants found not guilty by reason of insanity are not automatically set free. They are usually confined to a mental institution until their sanity is established. These defendants can spend more time in a mental institution than they would have spent in prison had they been convicted.

• An insanity defense normally rests on the testimony of a psychiatrist, who testifies for the defendant after examining him and his past history, and the facts of the case. Courts appoint psychiatrists at government expense to assist poor defendants who cannot afford to hire their own psychiatrists.

• Once a defendant raises his or her sanity as a defense, he or she must submit to psychological tests conducted at the behest of the prosecution. This can be a very painful and humiliating experience, one that many defendants choose to forgo rather than rely on the insanity defense.