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Criminal Law • Excuse
CRIMLAW#021
Legal Definition
Under the irresistible impulse test, a defendant is insane where, due to a mental illness, he was unable to control his actions or conform his conduct to the law.
Plain English Explanation
"Criminal Laws" are rules that society has agreed are so important to follow that society allows the government to punish those who break them. However, in general, society wants to be fair when it comes to applying punishment.
It arguably isn't fair to punish someone for doing something when they didn't "intend" to do it because they suffer from insanity. In other words, if you imagine your body as being a vehicle driven and operated by the brain, what happens when the brain glitches and the body responds by doing something that wasn't actually consciously intended? This is where we get into the land of sanity, and there are a few important tests to know which will be useful in trying to argue that someone who isn't mentally healthy shouldn't be held liable for crimes they technically committed:
(1) The M'Naghten Test states that a defendant is insane if they have some "mental disease" that prevents them from either (a) not realizing their actions were wrong (e.g., the defendant shot someone dead because God told them they needed to in order to save the planet from being exploded), or (b) not understand what it is they were doing as they did it. (e.g., the defendant believed they were hitting a baseball with a baseball bat, but in reality they were hitting a person's head with a bat."
(2) The Irresistible Impulse Test states that a defendant is insane if they have a mental disorder that prevents them from controlling their actions or conforming to the law. In other words, a defendant can be deemed insane under the Irresistible Impulse Test even if they were well aware of their actions and that their actions were wrong so long as they were unable to control their actions. In contrast, such an awareness of action and wrongdoing would fail the M'Naghten Test.
(3) The Durham Test is one of the more broad tests available, and is less commonly used. It is simply a "but for" test, which means so long as the Jury decides that the defendant's actions are a direct result of mental illness, then the defendant is not sane.
(4) Finally, the Model Penal Code ("MPC") tests essentially combine M'Naghten and Irresistible Impulse. Under this test, a defendant is insane if either (a) they lack the capacity to appreciate the criminality of their conduct (like M'Naghten), or (b) they cannot conform their conduct to the requirements of the law.
It arguably isn't fair to punish someone for doing something when they didn't "intend" to do it because they suffer from insanity. In other words, if you imagine your body as being a vehicle driven and operated by the brain, what happens when the brain glitches and the body responds by doing something that wasn't actually consciously intended? This is where we get into the land of sanity, and there are a few important tests to know which will be useful in trying to argue that someone who isn't mentally healthy shouldn't be held liable for crimes they technically committed:
(1) The M'Naghten Test states that a defendant is insane if they have some "mental disease" that prevents them from either (a) not realizing their actions were wrong (e.g., the defendant shot someone dead because God told them they needed to in order to save the planet from being exploded), or (b) not understand what it is they were doing as they did it. (e.g., the defendant believed they were hitting a baseball with a baseball bat, but in reality they were hitting a person's head with a bat."
(2) The Irresistible Impulse Test states that a defendant is insane if they have a mental disorder that prevents them from controlling their actions or conforming to the law. In other words, a defendant can be deemed insane under the Irresistible Impulse Test even if they were well aware of their actions and that their actions were wrong so long as they were unable to control their actions. In contrast, such an awareness of action and wrongdoing would fail the M'Naghten Test.
(3) The Durham Test is one of the more broad tests available, and is less commonly used. It is simply a "but for" test, which means so long as the Jury decides that the defendant's actions are a direct result of mental illness, then the defendant is not sane.
(4) Finally, the Model Penal Code ("MPC") tests essentially combine M'Naghten and Irresistible Impulse. Under this test, a defendant is insane if either (a) they lack the capacity to appreciate the criminality of their conduct (like M'Naghten), or (b) they cannot conform their conduct to the requirements of the law.
Hypothetical
Hypo 1: Bob is laying in bed one night. He gets hungry and decides to make a sandwich. He walks down his hallway, into the kitchen, takes out a knife, and begins slicing into a turkey. In reality, Bob had walked out of his house and into Sam's house and is slicing off pieces of Sam. Result: Under the M'Naghten test, Bob is insane because he was not aware of the nature of his actions. He believed he was making a sandwich, not slicing Sam into pieces. The Irresistible Impulse test is not applicable. The Durham Test is likely applicable, but would require a jury to find that Bob's actions were a result of some mental disease. The Model Penal Code test would also be applicable for the same reason that the M'Naghten applies.
Hypo 2: Bob believes Sam is a bad person. A voice in Bob's head encourages Bob to kill Sam. Bob decides to kill Sam even though he knows he will get in trouble for it. Result: M'Naghten doesn't apply here. Bob is aware of his actions (he is aware that he is going to kill Sam), and he is aware that his actions are wrong. The Irresistible Impulse test doesn't apply either. Though Bob was encouraged by the voice in his head, he wasn't compelled to do so because of them. Rather, the voices "won him over." He clearly resisted them for a while, but then decided to change his mind. Durham Test could apply, but it may be a stretch. After all, the facts seem to state that Bob already wanted to kill Sam, so it would be difficult to argue that but for the voice in his head, he would have never followed through. Finally, the MPC Test also fails, since it is just a combination of M'Naghten and Irresistible Impulse.
Hypo 3: Bob believes Sam is a bad person. Bob believes that Sam has been sent by Lucifer to destroy the world and that if Bob doesn't stop Sam immediately, Sam will psychically explode the planet. Bob kills Sam to save the world. Result: Under M'Naghten, Bob is aware of the nature of his actions (he intended to kill Sam and then did), but he genuinely believes that killing Sam is a good thing because, after all, Bob believes Sam was sent by Lucifer to explode the planet, so why wouldn't he think society would support him killing Sam? Thus, he would be insane under M'Naghten. Irresistible Impulse would not apply here. Durham Test would apply, if a jury believes Sam's killing happened as a result of Bob's mental disease. Finally, Bob would also be insane under the MPC Test since it falls under M'Naghten.
Hypo 4: Bob suffers from kleptomania (a recurrent urge to steal). One day, while walking through a store, he steals something and is caught. Result: M'Naghten may apply, but we'd need more facts. It's possible that Bob realizes he suffers from kleptomania and is ashamed at the fact that he steals so much. Under the Irresistible Impulse test, Bob may be acquitted if he is genuinely incapable of controlling himself from stealing due to his mental illness. Durham Test may also apply if the jury believes it is a fit. Finally, because Irresistible Impulse applies, so the MPC Test would apply as well.
Hypo 2: Bob believes Sam is a bad person. A voice in Bob's head encourages Bob to kill Sam. Bob decides to kill Sam even though he knows he will get in trouble for it. Result: M'Naghten doesn't apply here. Bob is aware of his actions (he is aware that he is going to kill Sam), and he is aware that his actions are wrong. The Irresistible Impulse test doesn't apply either. Though Bob was encouraged by the voice in his head, he wasn't compelled to do so because of them. Rather, the voices "won him over." He clearly resisted them for a while, but then decided to change his mind. Durham Test could apply, but it may be a stretch. After all, the facts seem to state that Bob already wanted to kill Sam, so it would be difficult to argue that but for the voice in his head, he would have never followed through. Finally, the MPC Test also fails, since it is just a combination of M'Naghten and Irresistible Impulse.
Hypo 3: Bob believes Sam is a bad person. Bob believes that Sam has been sent by Lucifer to destroy the world and that if Bob doesn't stop Sam immediately, Sam will psychically explode the planet. Bob kills Sam to save the world. Result: Under M'Naghten, Bob is aware of the nature of his actions (he intended to kill Sam and then did), but he genuinely believes that killing Sam is a good thing because, after all, Bob believes Sam was sent by Lucifer to explode the planet, so why wouldn't he think society would support him killing Sam? Thus, he would be insane under M'Naghten. Irresistible Impulse would not apply here. Durham Test would apply, if a jury believes Sam's killing happened as a result of Bob's mental disease. Finally, Bob would also be insane under the MPC Test since it falls under M'Naghten.
Hypo 4: Bob suffers from kleptomania (a recurrent urge to steal). One day, while walking through a store, he steals something and is caught. Result: M'Naghten may apply, but we'd need more facts. It's possible that Bob realizes he suffers from kleptomania and is ashamed at the fact that he steals so much. Under the Irresistible Impulse test, Bob may be acquitted if he is genuinely incapable of controlling himself from stealing due to his mental illness. Durham Test may also apply if the jury believes it is a fit. Finally, because Irresistible Impulse applies, so the MPC Test would apply as well.
Related Concepts
How does the age of a perpetrator affect their criminal liability?
Under the Durham Test ("But For"), when is a defendant insane?
Under the M'Naghten Test (cognitive), when is a defendant insane?
Under the Model Penal Code test (M'Naghten + Irresistible Impulse), when is a defendant insane?
Under what circumstances is assault a specific or general intent crime?
What are the most common excuses to committing crimes?
What is aggravated kidnapping?
What is criminal battery?
What is involuntary intoxication, and when is it a valid defense?
What is kidnapping?
What is voluntary intoxication, and when is it a valid defense?
