The insanity defense, though common in popular media, is not that easy to execute in the real world. In fact, different states have their own standards for proving the insanity defense. Here are some of the most common variations of the insanity defense.
The M'Naghten Rule
In the M'Naghten Rule, a criminal defendant is deemed to have been insane at the time of the alleged act if they:
- Didn't know the nature of their crime
- Couldn't differentiate right from wrong
In some states, the defendant must meet both parts of the test while in others the defendant must only meet at least one of the tests. For example, a criminal defendant suffering from a psychiatric problem and attacks their neighbor because they believe the neighbor is the devil may be successful with this defense. Such a person doesn't know the nature of their crime because they believe they are attacking an evil, supernatural being.
The Irresistible Impulse Test
Critics of the M'Naghten Rule claim that this definition of insanity is more legal than medical, which make them consider the test weak. In seeking to make the insanity defense threshold stricter, some authorities came up with the Irresistible Impulse test. The Irresistible Impulse test builds upon the M'Naghten Rule by adding a third requirement of inability to control criminal impulses.
Basically, the test claims that a person who is not in full control of their actions should not be punished for the same actions. For example, a patient suffering from cognitive psychotic disorder may not even tell what is real and what is not – they lose contact with reality. This means a psychotic may do things that they don't even know about, and the Irresistible Impulse test would see them not convicted of their actions.
The Model Penal Code
The Model Penal Code for insanity defense has two elements: a defendant is found to be legally insane if they meet at least one of the tests, and the elements are:
- The defendant was unable to appreciate the criminality of their conduct
- The defendant was unable to conform their conduct to legal requirements
In this case, the defendant either has to be diagnosed with a specific mental condition first. After that, the powers that be determine whether the mental defect prevented the defendant from knowing right from wrong or from controlling their impulses. As you can see, the main difference between the Model Pena Code and the other two tests is that a mental health diagnosis is required here.
For more information, contact your local criminal defense law office.