Defenses and Exceptions



Insanity has a long of history of being pleaded by the accused as a defense to criminal actions. Since a crime generally requires intent, guilt (and a subsequent conviction) requires a mind free from severe mental defect or disability. Under this theory, if you do not know what you are doing, you cannot be guilty of the criminal behavior. The law regards an "insane" defendant as a person needing help, not punishment. Furthermore, punishment does not act as a deterrent to a person suffering from a mental disability.

Most states no longer use the term "insanity" as a legal definition. Laws now address the person as "severely mentally deficient or disabled," rather than "insane," at the time of the criminal act. Persons falling under these definitions may be "excused" from their crime. The case of John Hinckley's attempted assassination of President Reagan in 1981 is one of the most famous examples. Because of his severe mental deficiency, Hinckley was found not guilty by reason of insanity and committed to a psychiatric hospital, rather than being punished by being incarcerated in a prison.

Insanity, which is a defense, should be distinguished from situations where mental incapacity stems from a neurological condition. Incompetency is different than insanity. The mentally disabled individual may have only a child's understanding of her acts, making her incompetent to stand trial. In these situations, the court often relies on IQ tests in making a competency determination at a separate hearing. (See Incompetency below for a discussion of these issues.) On the other hand, the defendant who claims she was insane when she committed the criminal act is not necessarily incompetent to stand trial.

M'Naghten Test

This rule of law from an 1843 English case continues to be the basis in the United States today for allowing insanity defenses in homicide cases. Also known as the "right or wrong" test, the M'Naghten rule requires a defendant alleging insanity to prove that she was suffering from such a derangement of her mental process that she was incapable of knowing the nature of her criminal act. A defendant who does not understand that her crime is "wrong" cannot be convicted since guilt requires responsibility.

Irresistible Impulse Test

Obviously, psychiatric tests are more sophisticated today, and the M'Naghten rule has been broadened from a simple "right or wrong" inquiry to a determination of "irresistible impulse." Under this test, if the defendant, by reason of a mental disease or an abnormal mental state of passion, is unable to control her actions or impulses to commit a criminal act, she is not responsible for her crime.

American Law Institute (ALI) Substantial Capacity Test

The ALI, composed of medical and legal professionals, proposed a new test in 1962 in order to determine "insanity." The M'Naghten test and the concept of irresistible impulse were combined to form a broader standard based on modern psychiatry and medicine. Rather than requiring an absolute lack of knowing right from wrong, the ALI test requires a finding of substantial incapacity to distinguish between right and wrong. The test also incorporates findings relating to the defendant's impulses or ability to control her behavior.

Federal laws and most state laws currently require the defendant that is pleading not guilty by reason of insanity to prove, by a preponderance of the evidence, her mental incapacity at the time of the crime. In some states, proof of mental incapacity can still result in a criminal conviction if the state permits "guilty, but mentally ill" verdicts.

Do I have a right to plead insanity?

No. You have no constitutional right to allege that you were insane at the time you committed a crime, although it is a legal defense in most states and the federal courts. Some states prohibit any kind of mental incapacity defense.

Many states do not use the term "insanity" as a defense. Instead, you must show that you lack the mental capacity to stand trial, to have committed the crime and/or understand the possible sentence given to avoid a guilty verdict. The net result is that your mental state is an evidentiary question that goes to a specific element of the crime, rather than an automatic defense of all elements. For example, a defendant may have not had the capacity to plan a murder but did know right from wrong. In that situation, the defendant cannot be convicted of first degree or premeditated murder, but he can be convicted of a lesser degree of murder because he knew the act of killing was wrong.

If I plead insanity as a defense, does the prosecution have to prove I was sane and knew right from wrong?

No. In federal court and most states, insanity is an affirmative defense, which means that you have the burden of proving your mental state at the time of the criminal act. Although the prosecution must prove that you committed the crime, you must convince a jury that you could not distinguish right from wrong when you acted or were unable to control your behavior.

Since there is a presumption that a defendant is sane at the time the crime was committed, the prosecution has no obligation to present evidence of a sane mental condition in its efforts to obtain a conviction. However, once the defendant has shown evidence of insanity or raised a doubt as to his mental capacity, the burden shifts to the prosecution to prove sanity beyond a reasonable doubt.

Does the court or jury have to accept a medical diagnosis of insanity in deciding whether the defendant is responsible for his criminal behavior?

No. A medical diagnosis does not establish a legal finding of insanity. In criminal cases, "insanity" is a legal term, not a medical one. A medically insane person can still be cognizant of the criminal act for which he is being tried. The jury must decide that the mental condition excuses the criminal behavior.

In states where laws allow insanity as a defense, evidence of any past actions in your life that help the prosecution show you were not insane are admissible. For example, you attended college and received a degree. Behavior before and after the crime, such as planning it and then bragging to friends, may tend to show you were not incapacitated at the time of the crime.

I am under psychiatric care, taking medication for my condition and have been hospitalized recently. Can I be convicted of a crime?

Yes. None of those factors automatically make you unable to distinguish right from wrong. Confusion, paranoia, delusions, etc. are not necessarily incompatible with a finding that you are responsible for your criminal behavior.

My doctor says she can testify that I did not have the mental capacity to commit the crime with which I have been charged. Will this prove I am not guilty by reason of insanity?

No. The jury will not hear that testimony from your doctor. Federal courts have adopted a rule of evidence, which will not allow expert testimony at trial as to whether the defendant did or did not have the mental capacity to commit the crime. Many states have also adopted this rule. Your doctor can only testify to her observations, diagnosis and treatment. She cannot give a final opinion to the jury of your mental capacity at the actual time of the criminal act.

What type of evidence can be introduced to a jury to show insanity at the time of a criminal act?

Although every fact situation varies, some examples include medical testimony of continuing delusions near the time of the act and when taken into custody, along with a long history of psychosis; testimony from arresting officers of bizarre and erratic behavior; testimony from family members concerning a defendant's prior hallucinations, delusions, etc.

Sidebar: In some states, laws permit intoxication to be an affirmative defense for some crimes if you can show you could not have had the mental capacity to know your actions were criminal. Oklahoma, for example, allows the intoxication defense in first-degree murder trials based on the theory that the required intent to commit the crime was never formed. However, voluntary intoxication, which leads to diminished capacity, is not a mental disease or defect that will relieve you of responsibility for all criminal acts.

My brother refused to plead insanity as a defense although he is clearly incapacitated. Can the court or his attorney do anything to force an insanity plea?

Not really. Although the judge can question your brother to make sure he understands that he is waiving his insanity defense, the consequences of his actions and whether he is voluntarily refusing to assert insanity, if it appears his decision is his own, the court must accept his decision to forego an insanity defense.


A person must be competent in order to be tried for a crime. If, before or during trial, a defendant's competency is raised, the court will hold a separate hearing to determine if the defendant has the ability to understand the charges brought against her. Evidence must be brought to the court's attention that tends to show a bona fide doubt as to competency. The assertation, "I am incompetent" does not create a bona fide doubt.

Is incompetency the same as an insanity defense?

No. Incompetency means you do not have the present ability to consult with or assist your lawyer in your defense and understand the nature and consequences of the trial proceedings against you. If you are found incompetent, you must be committed to a mental facility until a time when you become competent to stand trial.

By pleading insanity as a defense, am I also raising the issue of my incompetency to stand trial?

No. A plea of insanity is not evidence of incompetency. Insanity pleas concern the time the offense was committed. Issues of competency go to your present ability to understand the proceedings against you.

How do I get a hearing on competency?

By bringing the issue to the court's attention. You need to show there is a bona fide doubt as to your competency by presenting facts to the court in motions and affidavits from credible sources and through your own attorney's statements concerning your ability to understand the proceedings. Additionally, the court is able to order a hearing based on the judge's own observations of your behavior during trial.

What types of behavior show incompetency?

Any behavior that indicates that you do not have the ability to understand the charges, the proceedings or consult rationally with your attorney such as:

  • loss of memory;
  • inability to recall the charges against you or conversations with your attorney about your case;
  • inability to describe the functions and duties of your attorney, the judge and jury; or
  • violent behavior toward those present in the courtroom.

Courts also consider recent severe mental illness, mental retardation or truly bizarre acts on the part of the defendant. Physical symptoms such as dizziness, nausea, headaches and high blood pressure alone are not evidence of incompetency.

Your attorney's view of your competency may carry the most weight with the court, since she is the best judge of your ability to assist in your defense. You may think you are incompetent, but if your attorney has not reached the same conclusion, the judge is unlikely to hold a hearing on the matter.

Who decides whether I am competent?

The judge. The jury will not hear any evidence regarding your competency. Whether or not you are competent to stand trial is in the sole discretion of the trial judge.

The defendant is sleeping during trial and generally not paying attention. Is he incompetent?

Unseemly behavior during trial is not enough to raise a doubt as to the defendant's competency.

Acting out in court and disrupting the proceedings will not get the defendant a hearing on incompetency. Bizarre behavior, such as praying out loud and singing in the courtroom is generally not enough to raise a bona fide doubt of competency and may, in fact, confirm the judge's suspicions that the defendant is staging the scenario.

My daughter has been in special education classes all her life because of learning disabilities. Is she competent to stand trial?

Yes. These facts do not raise a bona fide doubt regarding competency. Furthermore, if this is the only evidence presented to the court of incompetency, she will probably not get a hearing on the matter.

My husband has been found incompetent to stand trial. What happens now?

In federal court, your husband is required to be hospitalized for up to 4 months. During this time, doctors will determine if he can improve and attain the capacity to stand trial in the foreseeable future. As long as he remains incompetent, your husband will be confined to the mental hospital.

If he gains competency during hospitalization, a certificate is filed with the court clerk to that effect. The court holds another competency hearing to determine that the defendant is indeed competent, orders his discharge and sets a trial date.

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