Black-letter propositions
- 01
Insanity tests include M'Naghten cognitive incapacity, irresistible impulse, MPC substantial capacity, and federal cognitive formulations.
- 02
Voluntary intoxication may negate specific intent but generally not malice, recklessness, negligence, or general intent; involuntary intoxication can resemble insanity.
- 03
Duress traditionally requires imminent threat of death or serious injury, reasonable fear, and no safe escape; common law limits its use for homicide.
- 04
Reasonable mistake can negate general intent, while any honest mistake can negate specific intent if it defeats that intent.
- 05
Subjective entrapment requires government inducement and lack of predisposition; objective formulations focus on improper police methods.
Use this attack sequence under time
Frame the issue
Classify offense mental state.
Resolve the next checkpoint
Choose stated insanity or entrapment test.
Resolve the next checkpoint
Connect intoxication or mistake to an exact element.
Finish the conclusion
For duress, find threat, immediacy, alternatives, and offense limits.
Common wrong turns
- Mental illness is not automatically legal insanity.
- Voluntary intoxication is no defense to recklessness.
- Private inducement is not government entrapment.
Worked example
A person honestly but unreasonably believes a suitcase is his and takes it.
Larceny's specific intent to deprive another is absent if the ownership belief is honest, even if unreasonable.
Practice this topic
Mental-state defenses
Cornell describes the insanity defense as an affirmative defense in which the defendant admits the action but asserts lack of culpability due to mental illness, distinct from diminished capacity, which only negates intent and results in a plea to a lesser crime. A defendant who is incompetent, meaning incapable of rationally communicating with counsel or comprehending the proceedings, cannot stand trial.
Intoxication is a defense when a compromised mental state hindered the ability to form the necessary intent. Many states distinguish voluntary from involuntary intoxication, and Montana v. Egelhoff held states may eliminate the voluntary intoxication defense.
Other excuses
Duress is unlawful threats or coercive behavior causing someone to act as they otherwise would not, with imminent threat and no present means of protection in one court's definition. A mistake of fact is usually a defense so long as it is reasonable, and for specific intent crimes even an unreasonable mistake may work. Model Penal Code 2.04 makes ignorance or mistake a defense if it negatives the required mental state.
Entrapment is an affirmative defense where law enforcement induced a criminal act the defendant otherwise would not have committed. Under the subjective test used in many jurisdictions the defendant must show lack of predisposition and government inducement.
Cornell explains that the insanity defense is an affirmative defense and that competency to stand trial is a separate procedural question under due process. A defendant is incompetent if incapable of rationally communicating with counsel or comprehending the proceedings. Keep the two questions apart: competence at trial and mental state at the time of the offense.
Frequently asked questions
What is the controlling rule for insanity, intoxication, duress, mistake, and entrapment?+
Excuse and mistake defenses must be matched to the offense's precise mental state and the jurisdiction's stated capacity, coercion, or inducement test.
What is the most common insanity, intoxication, duress, mistake, and entrapment trap?+
Mental illness is not automatically legal insanity. Voluntary intoxication is no defense to recklessness. Private inducement is not government entrapment.
What is the insanity defense?+
An affirmative defense in which the defendant admits the act but asserts lack of culpability due to mental illness.
How does diminished capacity differ from insanity?+
Diminished capacity negates the element of intent and results in a plea to a lesser crime, while insanity is a full defense, according to Cornell.
Can voluntary intoxication be a defense?+
It varies by state. Montana v. Egelhoff held states may constitutionally eliminate the voluntary intoxication defense, and Cornell says many have.
When is a mistake of fact a defense?+
Usually if reasonable, and for specific intent crimes even an unreasonable mistake may work, per Cornell's summary.
What does the subjective entrapment test require?+
That the defendant lacked a predisposition to commit the crime and that the government induced the defendant to commit it.