Many states and the federal courts recognize defenses to criminal charges in limited circumstances when the defendant was under duress or committed the criminal offense out of necessity to avoid death or serious bodily injury. The definitions for these affirmative defenses vary from state to state and in the federal courts, with some jurisdictions treating them as the same defense, and others making the distinction that duress applies when a defendant committed the crime because someone forced them to do it, and necessity applies when the defendant was confronted with bad alternatives in an emergency situation and chose the best alternative.

The elements of the defense of duress or necessity are that (1) the defendant was facing an unlawful and imminent threat sufficient to create a reasonable apprehension of death or serious bodily injury; (2) the defendant had not recklessly or negligently placed himself in a situation where he would likely be forced to commit a criminal act; (3) the defendant had no reasonable, legal alternative to violating the law; and (4) the defendant could have reasonably believed that the commission of the criminal act would avoid the threatened harm.

Duress and necessity defenses to criminal charges may be located in a state’s court opinions or cases (common law) or in its statutes—usually in the penal or criminal code. Many states have pattern or form jury charges (questions and instructions) and include a question that may be given to the jury to determine whether the defendant’s conduct is excused by the defense of duress or necessity.

In Pennsylvania, the defenses of duress and necessity are recognized as potential justifications for criminal conduct under limited circumstances. These affirmative defenses are distinct from each other. Duress occurs when a person commits a crime because they were coerced by an imminent threat of death or serious bodily injury, while necessity is invoked when a person is faced with an emergency situation that leaves them with no lawful alternative but to commit a crime to avoid greater harm. The elements required for these defenses typically include an immediate threat of unlawful force, no contribution by the defendant to the situation, no viable alternative, and a reasonable belief that the criminal act would prevent the harm. These defenses can be found in Pennsylvania's case law as well as in its statutes. Pennsylvania law would require the defendant to prove these elements to the satisfaction of the court or jury, and if successful, the defenses can result in the defendant being excused from criminal liability. It is important for anyone considering these defenses to consult with an attorney to understand the specific requirements and likelihood of success in their particular case.