The insanity defense is an idea many Americans love to hate. Television shows and talk radio often bring us vague but angry stories about hardened criminals who “plead insanity” and then “walk.” As a result, many Americans, including some jurors and some people accused of crimes, have false views about the insanity defense.

Each state has its own way of defining insanity. While mental health experts sometimes testify in trials, state standards for insanity are not medical but legal. To argue someone is not guilty by reason of insanity, you need to understand state laws and criminal procedures.

Guilt is different from fitness to stand trial

First, remember that the issue is not whether the defendant is now insane. Thus, it is irrelevant whether a defendant “seems sane.” That issue might matter in deciding whether they are currently “competent to stand trial,” which is typically an entirely separate problem.

Instead, the defendant’s sanity when they committed the crime is the question before the court.

What are you trying to prove?

In some states, the question is whether mental illness led the person to commit the crime. Pleading insanity suggests they would not have done it “but for” the mental illness. This is not the question in Texas.

Other states judge whether the person was unable to understand the idea of crime or criminality. Pleading insanity suggests they could not grasp the notion of breaking laws. This is also not the question in Texas.

Texas uses a variation of probably the oldest and most strict of the insanity standards, known as M’Naghten’s Rule. Here, the question is whether the defendant’s “severe mental disease or defect” kept them from knowing that their “conduct was wrong.” Pleading insanity means the defendant’s mental illness caused them to be unable to choose right from wrong.

If you meet your burden of proof, what happens then?

In other criminal trials, the defendant is innocent until the prosecution proves the defendant is guilty beyond a reasonable doubt. In an insanity defense, the burden of proving the defendant is not guilty by reason of insanity is on the defendant.

If the case results in the defendant proving that they are insane, the next step is generally that a Texas state hospital takes the defendant for confinement and treatment. The length of time they spend in the hospital is not meant to be longer than the amount of time they would have spent in prison had a jury found them sane and guilty.