By Linda Sanabria, J.D. | Legally reviewed by Melissa Bender, Esq. | Last reviewed November 28, 2023
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When a criminal defendant can prove they lacked the mental capacity to commit a given crime, they may be found not guilty because of insanity. In these cases, the defendant may receive mental health treatment in an institution and be prevented from leaving if they're considered a danger to society.
Four states (Kansas, Montana, Idaho, and Utah) explicitly don't allow for the insanity defense. In other states, the requirements of the law for proving this defense vary widely. States that allow for the insanity defense use one (or a combination) of the following legal standards:
States generally follow one of the four legal standards for determining insanity as an affirmative defense against criminal standards, but they often combine these standards or follow their own modified interpretation. The following provides the status of the insanity defense in each jurisdiction.
| State | Insanity Defense Rules |
|---|---|
| Alabama | The state uses the M'Naghten Rule. The burden of proof is on the defendant. |
| Alaska | The state uses a modified M'Naghten Rule. The burden of proof is on the defendant. A guilty but mentally ill verdict is allowed. |
| Arizona | The state uses a modified M'Naghten Rule. The burden of proof is on the defendant. A guilty but insane verdict is allowed. |
| Arkansas | The state uses a modified Model Penal Code rule. The burden of proof is on the defendant. |
| California | The state uses the M'Naghten Rule. The burden of proof is on the defendant. |
| Colorado | The state uses a modified M'Naghten Rule with the Irresistible Impulse Test. The burden of proof is on the state. |
| Connecticut | The state uses a modified version of the Model Penal Code rule. The burden of proof is on the defendant. |
| Delaware | The state uses a modified version of the Model Penal Code rule. The burden of proof is on the defendant. |
| District of Columbia | The state uses the Model Penal Code rule. The burden of proof is on the defendant. |
| Florida | The state uses the M'Naghten Test. The burden of proof is on the state. |
| Georgia | The state uses a modified version of the M'Naghten Rule. The burden of proof is on the defendant. A guilty but mentally ill verdict is allowed. |
| Hawaii | The state uses the Model Penal Code rule. The burden of proof is on the defendant. |
| Idaho | The state has abolished the insanity defense. The state allows a guilty but insane verdict. |
| Illinois | The state uses a modified version of the Model Penal Code rule. The burden of proof is on the defendant. |
| Indiana | The state uses a modified version of the Model Penal Code rule. The burden of proof is on the defendant. |
| Iowa | The state uses the M'Naghten Rule. The burden of proof is on the defendant. |
| Kansas | The state has abolished the insanity defense. |
| Kentucky | The state uses the Model Penal Code rule. The burden of proof is on the defendant. |
| Louisiana | The state uses the M'Naghten Rule. The burden of proof is on the defendant. |
| Maine | The state uses a modified version of the Model Penal Code rule. The burden of proof is on the defendant. |
| Maryland | The state uses the Model Penal Code rule. The burden of proof is on the defendant. |
| Massachusetts | The state uses the Model Penal Code rule. The burden of proof is on the state. |
| Michigan | The state uses the Model Penal Code rule. The burden of proof is on the state. |
| Minnesota | The state uses the M'Naghten Rule. The burden of proof is on the defendant. |
| Mississippi | The state uses the M'Naghten Rule. The burden of proof is on the state. An acquitted by reason of insanity verdict is allowed. |
| Missouri | The state uses a modified version of the M'Naghten Rule. The burden of proof is on the defendant. |
| Montana | The state has abolished the insanity defense, although a guilty but insane verdict is allowed. |
| Nebraska | The state uses the M'Naghten Rule. The burden of proof is on the defendant. |
| Nevada | The state uses the M'Naghten Rule. The burden of proof is on the defendant. |
| New Hampshire | The state uses the Durham standard. The burden of proof is on the defendant. |
| New Jersey | The state uses the M'Naghten Rule. The burden of proof is on the state. |
| New Mexico | The state uses the M'Naghten Rule with the Irresistible Impulse Test. The burden of proof is on the state. |
| New York | The state uses the Model Penal Code rule. The burden of proof is on the defendant. |
| North Carolina | The state uses the M'Naghten Rule. The burden of proof is on the defendant. |
| North Dakota | The state uses the Model Penal Code rule. The burden of proof is on the state. |
| Ohio | The state uses the M'Naghten Rule. The burden of proof is on the defendant. |
| Oklahoma | The state uses the M'Naghten Rule. The burden of proof is on the state. |
| Oregon | The state uses the Model Penal Code rule. The burden of proof is on the defendant. |
| Pennsylvania | The state uses the M'Naghten Rule. The burden of proof is on the defendant. |
| Rhode Island | The state uses the Model Penal Code rule. The burden of proof is on the defendant. |
| South Carolina | The state uses the M'Naghten Rule. The burden of proof is on the defendant. |
| South Dakota | The state uses the M'Naghten Rule. The burden of proof is on the defendant. |
| Tennessee | The state uses the Model Penal Code rule. The burden of proof is on the state. |
| Texas | The state uses the M'Naghten Rule with the Irresistible Impulse Test. The burden of proof is on the defendant. |
| Utah | The state has abolished the insanity defense, but guilty but mentally ill verdicts are allowed. |
| Vermont | The state uses the Model Penal Code rule. The burden of proof is on the defendant. |
| Virginia | The state uses the M'Naghten Rule with the Irresistible Impulse Test. The burden of proof is on the defendant. |
| Washington | The state uses the M'Naghten Rule. The burden of proof is on the defendant. |
| West Virginia | The state uses the Model Penal Code rule. The burden of proof is on the state. |
| Wisconsin | The state uses the Model Penal Code rule. The burden of proof is on the defendant. |
| Wyoming | The state uses the Model Penal Code rule. The burden of proof is on the defendant. |
The defense of insanity has been a hot topic of discussion among lawyers and the public for decades, questioning the competency of some defendants and raising reasonable doubt. If you have any questions about someone's mental condition in relation to the insanity defense, get in touch with a local criminal defense attorney as soon as possible. If you're facing a criminal case, it's important to have a strong advocate on your side.
Contact a qualified criminal lawyer to make sure your rights are protected.
Get tailored advice and ask your legal questions. Many attorneys offer free consultations.