How Defendants' Mental States Affect Their Responsibility for a Crime

Criminal intent—also called "mens rea"—is an element of some, but not all, crimes.

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What makes a crime a crime? In most cases, an act is a crime because the person committing it intended to do something that the state legislature or Congress has determined is wrong, also known as criminal intent. This mental state is generally referred to as "mens rea," Latin for "guilty mind."

The "mens rea" concept is based on a belief that people should be punished only when they have acted in a way that makes them morally blameworthy. In the legal system's eyes, people who intentionally engage in the behavior prohibited by a law are morally blameworthy.

Careless Behavior

"Ordinary" carelessness is not a crime. For example, careless ("negligent") drivers are not usually criminally prosecuted if they cause an accident, though they may have to pay civil damages to those harmed by their negligence.

However, more-than-ordinary carelessness ("recklessness" or "criminal negligence") can amount to mens rea. In general, carelessness can be a crime when a person "recklessly disregards a substantial and unjustifiable risk." It's up to judges and juries to evaluate a person's conduct according to community standards and decide whether the carelessness is serious enough to demonstrate mens rea. (See What is criminal negligence? and What amounts to recklessness?)

Unintentional vs. Intentional Conduct

People who unintentionally engage in illegal conduct may be morally innocent; this is known as making a "mistake of fact." Someone who breaks the law because he or she honestly misperceives reality lacks mens rea and should not be charged with or convicted of a crime. For example, if Paul Smith hits Jonas Sack because he reasonably but mistakenly thought Sack was about to hit him, Smith would not have mens rea.

While a "mistake of fact" can negate mens rea, a "mistake of law" usually cannot. Even when people don't realize what they are doing is illegal, if they intentionally commit the act, they are almost always guilty. For example, if Jo sells cocaine believing that it is sugar, Jo has made a mistake of fact and lacks mens rea. However, if Jo sells cocaine in the honest but mistaken belief that it is legal to do so, Jo will have mens rea since she intentionally committed the act. Perhaps the best explanation for the difference is that if a "mistake of law" allowed people to escape punishment, the legal system would encourage people to remain ignorant of legal rules.

Crimes Requiring "Knowing" Engagement in Criminal Conduct

Some laws punish only violators who "knowingly" engage in illegal conduct. What a person has to "know" to be guilty of a crime depends on the behavior that a law makes illegal. For example:

  • A drug law makes it illegal for a person to "knowingly" import an illegal drug into the United States. To convict a defendant of this crime, the prosecution would have to prove that a defendant knew that what he brought into the United States was an illegal drug.
  • Another drug law makes it illegal to furnish drug paraphernalia with "knowledge" that it will be used to cultivate or ingest an illegal drug. To convict a defendant of this crime, the prosecution would have to prove that a defendant who sold or supplied drug paraphernalia knew about the improper purposes to which the paraphernalia would be put.

Crimes Requiring "Malicious" or "Willful" Behavior

In everyday usage people often use the term "malicious" to mean "spiteful" or "wicked." In most criminal statutes, however, "malicious" is synonymous with "intentional" and "knowing." As a result, the term "maliciously" usually adds nothing to the general mens rea requirement.

As used in murder statutes, however, the term "malice" is often interpreted as meaning the defendant had a "man-endangering" state of mind when the act was committed, which is enough to justify at least a second degree murder charge.

As with "maliciously," the term "willfully" usually adds nothing to the general mens rea requirement. At times, however, the term "willfully" in a statute has been interpreted to require the government to prove not only that a person acted intentionally, but also that the person intended to break the law. (This is an unusual instance in which "ignorance of the law" actually is an excuse!) For example, in one case a federal law made it illegal to willfully bring in to the country more than $10,000 in cash without declaring it to customs officials. The U.S. Supreme Court decided that to convict a person of violating this law, the government had to prove that the person knew the law's requirements. (Ratzlaf v. U.S., 510 U.S. 135 (1994).)

"Specific Intent" Crimes

"Specific intent" laws require the government to do more than show that a defendant acted "knowingly." Specific intent laws require the government to prove that a defendant had a particular purpose in mind when engaging in illegal conduct. (For more, see General Intent Crimes vs. Specific Intent Crimes.)

For example, many theft laws require the government to prove that a defendant took property "with the intent to permanently deprive a person of the property." To convict a defendant of theft, the government has to prove that a thief's plan was to forever part a victim from his or her property. For example, a culprit who drives off in another's car without permission and returns it a few hours later might be convicted only of "joyriding." However, the same culprit who drives off in another's car without permission and takes it across the country probably demonstrates a specific intent to permanently deprive the owner of the car and would be guilty of the more serious crime of car theft.

The Role of "Motive" in Criminal Law

"Motive" generally refers to the reason behind an illegal act. For example, a person's need to raise money quickly to pay off a bookie may be the motive for a robbery, while revenge for a personal affront may be the motive for a physical attack. Prosecutors often offer motive evidence as circumstantial evidence that a defendant acted intentionally or knowingly. Judges and jurors are more likely to believe that a defendant had mens rea if they know that the defendant had a motive to commit an illegal act. By the same token, defendants may offer evidence showing that they had no motive to commit a crime and then argue that the lack of a motive demonstrates reasonable doubt of guilt.

Crimes That Don't Require Mens Rea

Laws that don't require mens rea -- that is, laws that punish people who may be morally innocent -- are called "strict liability" laws. The usual justification for a strict liability law is that the social benefits of stringent enforcement outweigh the harm of punishing a person who may be morally blameless. Examples of strict liability laws include:

  • "Statutory rape" laws, which in some states make it illegal to have sexual intercourse with a minor, even if the defendant honestly and reasonably believed that the sexual partner was old enough to consent legally to sexual intercourse.
  • "Sale of alcohol to minors" laws, which in many states punish store clerks who sell alcohol to minors even if the clerks reasonably believe that the minors are old enough to buy liquor.

Strict liability laws like these punish defendants who make honest mistakes and therefore may be morally innocent.

For More Information

To learn more about every phase of the criminal justice process, see The Criminal Law Handbook: Know Your Rights, Survive the System, by Paul Bergman and Sara Berman (Nolo).

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