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When a criminal suspect is able to prove they lacked the mental capacity to commit a given crime, they may be found not guilty by reason of insanity. In these cases, the defendant may receive treatment in an institution and will be prevented from leaving if they're considered a danger to society. Four states, including Kansas, Montana, Idaho, Utah, don't explicitly allow for the insanity defense. In other states, the criteria 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 a 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.
| Alabama | The state uses the M'Naghten Rule. The burden of proof is on the defendant. |
| Alaska | 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. |
| Arizona | The state uses a modified version of the M'Naghten Rule. The burden of proof is on the defendant. A guilty but insane verdict is allowed. |
| Arkansas | The state uses a modified version of the 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 version of the 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 Rule. 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 insanity defense has been a hot topic of discussion among lawyers and the general public for decades. Whether your state's insanity definition focuses on "capacity to form a criminal intent," or "ability to differentiate between right and wrong," or "ability to appreciate the criminal nature of one's actions," the issue becomes gravely important if you or a loved one has been charged with a crime. If any of these issues apply to you, your best move is to get in touch with a local criminal defense lawyer as soon as possible.
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