Mens Rea

Mens rea (pronounced “menz ray-ə”) is simply the framework within the law that determines a defendant’s culpability for a crime. Latin for “guilty mind,” mens rea specifically refers to what the accused was thinking at or shortly before a crime was allegedly committed. The mens rea required for conviction varies between crimes; in some cases it requires an intentional act while in others only a negligent act is necessary. To get a better understanding of these concepts, see the mens rea definition below.

Mens Rea Definition


The state of mind that the prosecution, to secure a conviction, must prove that a defendant had when committing a crime

One of the two necessary elements of a crime under common law, along with actus reus.

Mens Rea Origin

The concept of mens rea and actus reus became integrated with British common law thanks to the writings of the English jurist Edward Coke. Coke wrote that to be culpable for a crime, a defendant must not only have committed the act (actus reus) but also had guilty intent in their mind (mens rea). The concept that someone who acts without mental fault cannot be liable of a crime is a foundation of due process.

While issues of intent are present in certain areas of civil law like breach of contract, mens rea is a legal concept that applies directly to criminal law. In modern times, many jurisdictions are replacing the term mens rea with plain English terminology including “fault elements” or “mental elements.”

Modes of Culpability

Under the common law, the concept of mens rea was an either/or issue; either you had the guilty mind of the crime in question or you didn’t. But under modern law, many jurisdictions with due process rights have created different levels, known as modes of culpability. This approach allows for more flexibility, as the mindset for committing an intentional murder is different from that of negligently building an apartment building that lacks proper fire escapes.

Culpability under the United States Model Penal Code

In the United States, the Model Penal Code has formulated multiple levels of culpability that have replaced the traditional mens rea. The varying levels of culpability are complex, and they contain some subtle distinctions. Since 1957, the Code has outlined five different levels of culpability, which include:

  • Negligently
  • Recklessly
  • Knowingly
  • Purposefully
  • Strict Liability


Negligence is the mildest of the modes of criminal culpability. You are found to have acted negligently when you fail to meet a reasonable standard of care that a person in your circumstances would ordinarily adhere to. There is no requirement of intent whatsoever; in fact you can act negligently when the thought of committing a crime hasn’t entered your mind.


Reckless conduct is a step above negligent conduct. A reckless action is one that is taken even when you know the associated risks. In other words, you act recklessly when you unintentionally harm someone so long as you knew your behavior carried the risk of that harm.


Acting with knowledge is a step above acting recklessly. While reckless behavior involves acting despite knowing of associated risks, this level of culpability applies when you know the behavior will result in a certain type of harm.


The highest level of culpability, acting with intent involves the explicit and conscious desire for a certain outcome. Acting purposefully is different from acting knowingly, in that purposeful action involves the resulting harm as your goal. Acting knowingly, on the other hand, is taking an action despite knowing the harm will result.

Strict Liability

Strict liability doesn’t technically fall within the other modes of culpability; in fact, it involves crimes that do not take account mens rea whatsoever.  Under a strict liability standard, it is the act itself that is worthy of the punishment independent of any outcome. Strict liability is more common in civil cases, but it is the standard in some criminal prosecutions.

Mens Rea Examples

It’s true that many of the mens rea present in Model Penal Code bleed into each other. It is easiest, then, to understand these concepts through the use of examples.

Examples of Acting Purposefully

Thelma and her new husband, Ted, have moved into a new home together. This is distressing news to Debra, Ted’s ex-girlfriend who was dumped by Ted for Thelma. Debra vowed to get her revenge, and the newlyweds moving in together has pushed Debra past her breaking point. In the middle of the night while Thelma and Ted are sleeping, Debra breaks into their new home. She barricades the door of their bedroom so that they are unable to escape and sets the house on fire. At the time she sets the fire, Debra intended for her ex and her hated rival to both perish in the flames. If Thelma and Ted die, Debra acted purposefully in their murder.

Examples of Acting Knowingly

Consider the same example as above. Thelma and Ted are still newlyweds with a new home, and Debra is still a jilted lover looking for revenge. However, this time Debra is aware that Thelma’s sister Tess is spending the night in their home. Debra’s purpose for setting the fire is to kill Thelma and Ted, and she is in no way motivated to kill Tess. However, she knows that Tess is in the home and that she will die in the fire if it is set. While Debra is acting purposefully in the killing of Thelma and Ted, she is acting knowingly in the killing of Tess.

Examples of Acting Recklessly

Consider the same example again. Thelma and Ted have recently purchased their new home, and Debra is enraged. Vowing revenge, Debra decides to burn down the newlyweds home on a night when she knows Thelma and Ted will be gone. Debra doesn’t intend to kill anyone, which is unfortunate since she is unaware Tess was housesitting that night. Next, Debra lights the home on fire, killing Tess. Debra didn’t purposefully murder Tess or even act knowing that the fire would result in her death. However, because she acted in a way that carried a substantial and unjustified risk that someone would be injured or killed, Debra has acted recklessly.

Examples of Acting Negligently

This time, Debra is still enraged at Thelma and Ted moving in together. However, she is unprepared to take any serious steps to get revenge. She does, however, drive by the couples’ home repeatedly. Each time she passes, she angrily flicks her stubbed out cigarettes into their yard. Debra didn’t have any intention of starting a fire and wasn’t aware that Tess was at the home housesitting. But because she should have known that flicking smoldering cigarettes into a yard could lead to a fire, any injuries Tess suffers from that fire would be because of the negligence of Debra.