Mens rea means criminal intent. An act must be blameworthy. An act must be done with criminal intent or be an act of gross negligence or recklessness. Mens rea is one of two components of a crime, the other being actus reus.
Mens Rea, Concurrence,
A criminal offense requires a criminal intent. The requirement of a criminal intent is based on moral blameworthiness, a conscious decision to knowingly engage in criminal conduct or to act in a reckless or negligent fashion. Mens rea consists of four states of mind. The most culpable is purposely, and then knowingly, recklessly, and negligently. Strict liability offenses require an actus reus, but do not incorporate a mens rea requirement. These typically are public welfare offenses or crimes that protect public safety by regulating food, drugs, and transportation.
On Culpability and Crime: The Treatment of Mens Rea in the Model Penal Code - Herbert Wechsler, Columbia Law School, ANNALS of the American Academy of Political and Social Science, Vol. 339, No.1 - When conduct has the external attributes of a crime, should further mental elements be required for conviction, and, if so, what should they be? Decisions have too frequently been imprecise in analysis and inconsistent in results, yielding a multitude of single instances which in the aggregate dilute the moral force that should attach to condemnation of behavior considered criminal.
Criminal liability may justly be based only upon conduct which includes a voluntary act or the omission to perform an act which the actor was physically able to perform. Act or omission are essential prerequisites to liability, but they are not sufficient to establish culpability.
The Model Penal Code proposes four concepts to describe the kinds of culpability which are sufficient to establish liability: purpose, knowledge, recklessness, or negligence. The doctrine of strict liability, ignorance and mistake of fact, intoxication, and ignorance and mistake of law are pertinent to establishing liability. One of the most contentious problems of the penal law concerns the criteria that should determine when individuals whose conduct would otherwise be criminal ought to be exculpated on the ground that they were suffering from mental disease or defect when they acted. The Model Penal Code would exculpate the person who, as a result of mental disease or defect, lacked substantial capacity either to appreciate the criminality of his conduct or to conform his behavior to the requirements of law.