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How a Defendant’s Mental States Can Affect Their Responsibility for a Crime

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An act is considered a crime when an individual commits what the state legislature or Congress deems wrong. It is known as criminal intent. According to Weber Law, this mental state is referred to as ‘mens rea’ or ‘guilty mind’.

It is a concept based on the belief that citizens may only be punished when they act in a way that makes them morally blameworthy. The legal system deems anyone who intentionally engages in behaviour prohibited by law as morally blameworthy.

For example, careless drivers aren’t usually criminally prosecuted if they are guilty of causing an accident. However, they must still pay civil damages to the victims due to their negligence. 

Yet, even though carelessness isn’t a crime, recklessness or criminal negligence is considered mens rea. Carelessness is considered a crime when an individual disregards a substantial or unjustifiable risk. Only the judges and juries can evaluate an individual’s conduct and ascertain if their carelessness was serious enough to demonstrate mens rea.

Mistake of fact vs mistake of law and mens rea

Someone may be morally innocent when they unintentionally engage in illegal conduct, which is labelled as a mistake of fact. For example, if John reasonably and mistakenly believes that Anthony is about to smack him, but John hits him first, then he would not have mens rea. 

He misperceived reality and shouldn’t be convicted of a crime. If John sells cocaine believing it is something else, he also lacks mens rea because he has made a mistake of fact. However, suppose John sells cocaine honestly believing it is legal. In that case, he will have mens rea since he intentionally committed the act. A mistake of law cannot negate mens rea, while a mistake of fact can do so.

Intent requirements and knowing engagements

You could be convicted of a crime if you committed it knowingly or intentionally. Specific intent laws dictate that prosecutors must demonstrate that a defendant acted knowingly and had a particular purpose in mind as they engaged in illegal conduct. 

For example, in a theft case, the prosecution must prove that the defendant intended to deprive another of their property permanently. Let’s say an individual steals a car but returns it after a couple of hours. They may be convicted of ‘joyriding’. However, suppose the individual takes the car across the country. In that case, it directly proves their will to permanently deprive the owner of their property, resulting in more serious criminal convictions.

If a person imports an illegal drug into a state, the prosecution has to prove that the defendant knew it was an illegal drug in that state. ‘Malicious’ or ‘willfully’ don’t usually add anything to the general mens rea requirement. However, sometimes, ‘willfully’ has been interpreted to require authorities to prove that the defendant intentionally broke the law. However, this also means that they have to prove that the individual knew about the law’s requirements.

When mens rea isn’t considered

Strict liability laws are laws that don’t require mens rea, and thus morally innocent people can be punished. Some examples include:

  • Statutory rape laws
  • Sale of alcohol to minors

These laws punish honest mistakes, and morally innocent defendants as excuses such as ‘I didn’t know they weren’t old enough to buy liquor’ or the defendant honestly believed that their sexual partner was old enough to consent legally don’t hold up.


Simona LeVey did her degree in psychology at Tel Aviv University. She is interested in mental health, wellness, and lifestyle.

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