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How Do You Prove Not Guilty by Reason of Insanity?

The "insanity defense" is one possible defense strategy you can use if you are facing criminal charges. You and your criminal defense attorney might claim that you are "not guilty by reason of insanity" in court.

Your defense will rely on evidence proving that you — the defendant — were "insane" when the alleged crime happened. A successful insanity defense means you are not criminally liable for breaking the law.

The Reality of Insanity Pleas

TV shows and movies portray defendants found not guilty by "reason of insanity." In real life, criminal defendants are not as successful with the insanity defense or "insanity plea" as popular media shows.

One study found that the insanity defense is only used in about 1% of all court cases. It is only successful in about 26% of those cases.

So, approximately one-quarter of 1% of cases in the U.S. criminal justice system end with a defendant being found not guilty because of insanity.

Insanity in Legal vs. Psychological Terms

In the legal world, the term "insanity" has a different meaning. It is not a medical definition of mental illness. You can be mentally ill and guilty of committing a crime. You can also be not guilty by reason of insanity and still be mentally ill. You can also use the insanity defense even if you have no history of mental illness.

The definition of insanity also varies among different jurisdictions (a court system, such as courts in your state vs. federal courts).

For a legal defense, the term insanity depends on the statutes and laws passed by legislatures and on case law which is developed in the courts.

To prove insanity, most jurisdictions require:

  • A professional assessment
  • Proof the defendant was not capable of distinguishing between right and wrong
  • Proof this mindset happened during the time of the offense (see temporary insanity below)

Some jurisdictions have an additional element. They allow a defendant to be found not guilty because of insanity if they were "unable to control their behavior at the time of the offense."

Other states have re-evaluated the defense and have decided to either eliminate or modify the insanity defense in their state.

What Happens When I Plead Insanity?

Usually, a defendant will need to have a complete mental evaluation as a first step when claiming insanity as a legal defense.

Psychiatrists or psychologists will take the witness stand in your court case. They will testify about your likely state of mind at the time of the offense.

However, even a professional alone can't decide whether a defendant is insane. As discussed above, insanity is a legal term when used as a criminal defense.

In the end, the jury or judge will decide whether the professional's testimony and other evidence support a finding of criminal insanity.

What Happens if the Court Finds Me Criminally Insane?

Defendants can be committed to a psychiatric hospital if they are found to be guilty of the alleged crimes or not guilty by reason of insanity.

While you might not face prison time, you could still spend mandatory time in a psychiatric hospital or "psych ward." In the past, state-run psychiatric facilities were called "insane asylums." This term is no longer used today. In some cases, it can be worse than being found guilty and going to prison.

Typically, the time commitment is not for a set amount of time. Defendants are committed until the individual is believed to no longer be a threat to society. Doctors ultimately have the power to make this subjective decision on when to release a defendant.

Temporary Insanity 101

A defense of "temporary insanity" is equally difficult to prove. If a defendant asserts temporary insanity as a defense, they are claiming that:

  • They were legally insane at the time of the alleged crime
  • They are lawfully sane now

Most states use one of the following four methods to determine temporary insanity:

  1. The M'Naghten Rule (sometimes called the right-wrong test): reviews mental defects that lead someone to believe in the rightness of their crime
  2. The Irresistible Impulse Test: reviews someone's awareness and willpower that led to the crime
  3. The Model Penal Code Test (also called the substantial capacity test): reviews the person's lack of ability to follow the law or see that a crime is wrong
  4. The Durham Rule (only used in New Hampshire): reviews the mental defect (such as paranoia) that caused the criminal conduct

If a court accepts the proof of temporary insanity and finds you not guilty, you are not likely to face time in a psychiatric facility.

The temporary insanity defense is rare. It is typically used for circumstances where events leading up to the criminal act had a direct impact on the commission of the crime itself. Common examples include:

  • Victims of emotional, sexual, or physical abuse
  • Family members seeking revenge for their victimized loved one
  • Victims of cults or other psychological tactics
  • People with unmedicated paranoid schizophrenia

Insanity Pleas in the Legal System

The successful use of the insanity defense may be rare. However, its existence provides a critical moral check on the legal system.

It allows the law to enforce treatment, rather than punishment, on people who can't understand their actions. Some people believe the insanity plea helps innocent victims of horrible circumstances and offers rehabilitation and a second chance to offenders.

Because these cases are complex, using an insanity defense is something that you should only attempt with the help of an experienced criminal defense attorney. An attorney will be able to examine your situation and help you determine whether this is actually the best option for mounting a defense.