Elements Of A Crime: Mens Rea And Actus Reus
Most crimes consist of two broad elements: mens rea and actus reus. Mens rea means to have "a guilty mind." The rationale behind the rule is that it is wrong for society to punish those who innocently cause harm. Actus reus literally means "guilty act," and generally refers to an overt act in furtherance of a crime. Requiring an overt act as part of a crime means that society has chosen to punish only bad deeds, not bad thoughts.
To constitute criminal behavior, the actus reus and the mens rea must occur simultaneously. For example, suppose John Doe shoots Bob Roe with the intent to kill, but misses completely. Doe later accidentally runs over Roe, resulting in Roe's death. Doe is not guilty of murder.
Different crimes require different degrees of intent. For example, to prove larceny, the prosecution must establish that the defendant intentionally took property to which he knows he is not entitled, intending to deprive the owner of possession permanently. Negligent homicide, on the other hand, involves thoughtlessness, inadvertence, or inattention in a person's duty to exercise due care toward others. A drunk driver who kills another is often charged with criminal negligent homicide.
Specific intent and general intent are other terms used to describe a person's state of mind. General intent means the intent to do something that the law prohibits; the prosecution does not need to establish that the defendant actually intended the precise result. Specific intent designates a special element above and beyond the actus reus, of the crime, and generally signifies an intentional or knowing state of mind. For example, in the case of larceny, the prosecution must establish the defendant's intent to steal the property. Statutes frequently employ terminology such as purposeful, knowing, reckless, or negligent to describe differing gradations of intent.
Intent is irrelevant in proving a strict liability crime. For a strict liability crime, a prosecutor need only prove that the forbidden act occurred. Statutory rape is a strict liability crime. Only the actus reus, a defendant's non-forcible sexual intercourse with a minor, is needed to establish criminal responsibility. The fact that a defendant might have made an honest and reasonable mistake as to the age of the victim is not a defense. Restrictions on the sale of alcohol are also strict liability offenses.
Intent on the part of the defendant is also often lacking in certain vicarious liability offenses. Vicarious liability offenses occur where a defendant's criminal liability is predicated upon the actions of another, often based upon an employer/employee relationship. For example, a bartender who serves alcohol to minors may, by his actions, make the bar owner criminally responsible. This may be true whether the bartender was acting on orders, or deliberately disobeying orders.
Actus reus requires a voluntary act. An epileptic who strikes another during a seizure has not committed a battery. On the other hand, an epileptic who knows he should not drive but does and causes injury, may be guilty of reckless criminal behavior because he created the dangerous situation. Moreover, a failure to act may also constitute a guilty act. Failure to fill out an income tax return is a violation of law. A lifeguard who allows a child to drown would almost certainly face criminal charges.