Legal Definitions - Model Penal Code Insanity Defense

The Model Penal Code Insanity Defense is a legal standard used to determine whether an individual should be held criminally responsible for their actions. Under this defense, a person may be found not guilty by reason of insanity if, at the time they committed a crime, they suffered from a severe mental disease or defect that significantly impaired their ability to do one of two things:

• Appreciate the wrongfulness of their actions: This means they lacked the substantial capacity to understand that what they were doing was morally or legally wrong.
• Conform their actions to the requirements of the law: This means they lacked the substantial capacity to control their behavior and follow legal rules, even if they might have understood that their actions were wrong.

In essence, this defense requires more than just having a mental illness; the illness must have been so severe that it fundamentally prevented the person from understanding the nature of their actions as wrong or from being able to stop themselves from committing the crime.

Examples:

• Example 1 (Inability to Appreciate Wrongfulness): Imagine a person named Alex who suffers from severe paranoid schizophrenia. During an acute psychotic episode, Alex genuinely believes that their neighbor, Mr. Henderson, is a dangerous alien entity attempting to abduct them. Acting on this profound delusion, Alex confronts and physically assaults Mr. Henderson, believing they are fighting for their life against a non-human threat. In this scenario, Alex might argue for the Model Penal Code insanity defense. While Alex physically harmed Mr. Henderson, their severe mental disease (paranoid schizophrenia) caused them to genuinely believe they were acting in self-defense against an alien, rather than committing an unlawful assault against a human. This severe delusion prevented Alex from having the substantial capacity to appreciate the wrongfulness of their actions as understood by society.

• Example 2 (Inability to Conform Conduct to Law): Consider Sarah, who has a rare neurological condition that, during periods of extreme stress, triggers sudden, uncontrollable violent outbursts akin to a temporary psychotic state. During one such episode, triggered by a minor workplace dispute, Sarah, despite a fleeting awareness that her actions were wrong, physically attacked a colleague, unable to stop herself once the episode began. Sarah might invoke the Model Penal Code insanity defense. Even if she possessed some understanding that assaulting her colleague was legally and morally wrong, her severe neurological condition, during an acute episode, could be argued to have deprived her of the substantial capacity to conform her actions to the requirements under the law. The defense would focus on her inability to control her behavior due to the mental defect, rather than a complete lack of understanding of wrongfulness.

• Example 3 (Combined Impairment in a Different Context): David suffers from a profound dissociative identity disorder (DID). During a severe dissociative episode, David experiences a "switch" to an alternate personality (an "alter") that is childlike and completely unaware of adult societal norms or legal consequences. While in this alter state, David enters a store and takes several items without paying, genuinely believing it's acceptable, much like a young child might. The primary personality, when aware, understands that theft is wrong. Here, David's defense could argue that at the moment of the theft, due to the severe mental defect of DID and the manifestation of a particular alter, he lacked the substantial capacity to appreciate the wrongfulness of his actions. The alter was genuinely unaware of the legal and moral implications of taking items without payment, effectively preventing David from understanding the wrongfulness at the time of the offense.