Defenses are available to defendants charged with crimes to justify their actions or otherwise dispute criminal liability for their conduct. Insanity is one such defense. Insanity under the law is not defined in the same way as the medical profession would define mental illness. It is a purely legal concept and who qualifies for this defense depends on where you are being prosecuted. There four accepted tests for Insanity used among the states.
The M’Naughten test is fairly common and is defined as a defense to crime when a disease or defect of the mind causes the defendant to lack the ability to understand the wrongfulness of his actions or to understand the nature and quality of his actions. This seems straightforward, but it can be difficult to overcome. Claiming insanity because voices in your head told you to kill your boss may not be successful in court if you knew killing was wrong and that the actions taken were violent and harmful. In contrast, suffering a delusion where you think you are at home doing dishes when you are really hacking someone to pieces with an axe will likely satisfy this test.
Irresistible Impulse Test
Under this test, the defendant must prove that he suffered a disease of the mind that made him unable to control his actions or conform his conduct to the law. Unlike the M’Naughten test, the defendant need not be unaware that his conduct is wrong. Essentially, this defense means that the circumstances are such that the defendant could not control himself. This is a common defense in cases involving vengeance.
The Durham test was an attempt to simplify the insanity defense while acknowledging the broad spectrum of debilitating mental illness that could explain otherwise deplorable conduct. This defense requires a causal connection between the conduct and a mental disease or defect. The conduct must be a product of the disease or defect in order to qualify for this defense.
Model Penal Code Test
Developed by the American Law Institute, the Model Penal Code test is what Illinois uses to define the insanity defense. Under this test, a defendant may be excused from criminal conduct is he suffered a mental disease or defect and lacked substantial capacity to either appreciate the criminality of his conduct or conform his conduct to the law.
The Illinois Legislature uses the following language to define the insanity defense under 720 ILCS 5/6-2:
“A person is not criminally responsible for conduct if at the time of such conduct, as a result of mental disease or defect, he lacks substantial capacity to appreciate the criminality of his conduct.”
This means that Illinois does not allow for the second option under this test that provides an excuse for not being able to conform one’s conduct to the law. Under this statute, the burden of proving this defense rests on the defendant by clear and convincing evidence. Further, suffering a mental illness but not being insane under this definition is not enough to qualify for this defense.
If you have questions about the insanity defense or need representation, contact a qualified Illinois Criminal Defense Attorney today.