Mens rea is a legal term referring to a “guilty mind,” or the intention to commit a crime. This intent to cause harm or break the law can be the distinguishing factor that separates a criminal liability from civil liability cases. Mens rea also helps to determine degrees of culpability and thus the severity of punishment in criminal cases.
In many law systems, there must be both a physical element, the actus reus, and a mental element, mens rea, to constitute a criminal charge. This mental element, however, is not a simple matter of being guilty or innocent. It can apply to intention to commit the crime; intention to commit a separate crime that resulted in further harm, recklessness; or criminal negligence. Consider, for example, a case in which someone died as the result of another person’s actions. The mindset of the accused, or existence of mens rea, will help determine the severity of the crime, allowing a court to rule the death either murder, manslaughter, or an excusable, lawful accident.
In a murder case, the prosecutor would have to prove that the accused had malicious aforethought, the most serious type of mens rea in a homicide case. This could include the intent to kill, the intent to cause serious bodily harm, the desire to commit a felony knowing it might result in homicide, or recklessness toward human life. Manslaughter, a homicide with a lower degree of culpability than murder, might be ruled voluntary or involuntary according to the nature of the mental element. During voluntary manslaughter, there was an intent to kill, but some factor, such as provocation, makes the killer less culpable.
In an involuntary manslaughter case, the accused person unintentionally kills someone while committing an unlawful act. In this situation, the mental element applies to the other unlawful act, but carries over to the homicide, making the accused more blameworthy than in an excusable accident. An excusable accident is not punishable because there was no mens rea and the death occurred while the person responsible was exercising normal caution and not breaking any laws.
Testing for mens rea in court may fall under any of three categories: subjective test, objective test, or a combination of the two, called a hybrid test. A subjective test occurs when evidence is submitted to prove a guilty mindset, such as the defendant’s admission or a diary outlining the defendant’s desire to knowingly commit a crime. An objective test of a guilty mindset determines whether a reasonable person would have connected the accused’s actions with harm or a breach of the law. A hybrid test is useful in amassing sufficient proof of a guilty mind or proving negligence, which may be clear when there is no subjective evidence of aforethought, but the objective test shows that a normal person would have foreseen the offense. If a person does not have normal reasoning capacities, due to age or mental illness, a guilty mind can often be argued to not exist.
While evidence of a mental element is typically needed to prove criminal liability, strict liability cases do not require proof of intent. Strict liability cases apply to certain offenses which can be punished regardless of the accused’s mindset, such as speeding. If proved, however, existence of mens rea can increase the punishment for such an offense.