What Is Mens Rea in U.S. Common Law?

A mens rea is a way of referring to a defendant’s state of mind and must be established before a defendant can be convicted of a particular crime. The four types of mens rea are ranked hierarchically, meaning that if it was established that a defendant had acted purposely rather than knowingly, the crime would carry a more severe punishment. 

•  Acting purposely: This term applies to a person who explicitly and consciously intends to commit a dangerous or illegal act. An example of acting purposely is when a defendant consciously targets a victim and then proceeds to assault the victim with the intent of inflicting harm. In this example, the defendant would be found to have acted with criminal intent. 
•  Acting knowingly: This term can be applied to a defendant who committed an act with the awareness that their actions will yield a particular result and preceding anyway. An example would be if a person acts in a way in which harm may not be their primary goal but rather a likely outcome, such as a heated argument in which someone is assaulted. 
•  Acting recklessly: This term is applied when a defendant consciously disregards substantial and unjustified risks. Someone who is driving under the influence may not intend or expect to hurt anyone. Nonetheless, taking the substantial risk of getting behind the wheel while intoxicated and proceeding to hurt someone, the defendant would meet the requirements for recklessness.
•  Acting negligently: Apply this term to a defendant who fails to meet a reasonable standard of behavior for their set of circumstances. A common example of criminal negligence is when a caretaker fails to execute their reasonable duties resulting in the injury of their child.

The subtleties of mens rea can only be argued by an experienced attorney with a clear understanding of the relevant statutes and pertinent case law. In a criminal case, it is vital to have the best representation possible in order to achieve a favorable result.