What a defendant intended to do can affect whether a crime has occurred.
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. 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.
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.
