There can be no crime of any nature without mens rea or an evil mind. Every crime requires a mental element and that is considered as the fundamental principle of criminal liability. The basic requirement of the principle mens rea is that the accused must have been aware of those elements in his act which make the crime with which he is charged.
Mens Rea in Indian Penal Code is indicated by means of words like dishonestly (section.24), fraudulently (section.25), Voluntarily (section.39),Good faith (section.52).
There is a well known maxim “actus non facit reum nisi mens sit rea” which means that, the guilty intention and guilty act together constitute a crime. It comes from the maxim that no person can be punished in a proceeding of criminal nature unless it can be showed that he had a guilty mind.
Actus Non Facit Reum Nisi Mens Sit Rea explains that for any act to be illegal in nature it must be done with a guilty mind. Thus to convict the defendant, it must be proved that the criminal act was carried out with a criminal intend. Not only is the act of the accused important but the intention of the accused to do the specific act is equally important to prove the guilt of the accused.
Thus it can be concluded that mere commission of a criminal act or breach of law is not sufficient to constitute a crime. It should be combined with the presence of wrongful intent. Further the mens rea is important to understand the severity of the crime committed. The essential ingredient is the blameworthy condition of the mind. Its absence can negate the liability.
However the statement without a guilty mind there is no crime is subjected to certain exceptions such as strict liability. Under strict liability, it is not necessary to show that a defendant possessed the relevant mens rea for the act committed.
This maxim can find its importance under section 14 of the Indian Evidence Act, 1872. It states that facts which indicate state of mind or intention are relevant facts in issue.
The two basic components of criminal law is Actus Reus and Mens Rea. Actus Reus is the wrongful act committed and Mens Rea is the state of mind behind such acts.
The Latin maxim Actus Non Facit Reum Nisi Mens Sit Rea is derived from Mens Rea. Actus Non Facit Reum Nisi Mens Sit Rea further explains as to how Mens Rea is applicable in criminal law. It states that a person is guilty of a criminal act only if such acts are accompanied by a criminal intention. This maxim is used to determine whether an act committed is criminal in nature or not. Several penal actions are required for crimes committed with specific intend and not for unanticipated or unintentional acts. However no breach of law can be left unpunished.
Thus this maxim is established to differentiate between intentional and unintentional criminal act so that the quantum of punishment can be decided accordingly.
When a person is attacked by another person with an intention to cause grievous hurt or injury then it is a crime. But when the person who was attacked causes injury to the other person in private defence then it is an unintentional act.
In the first scenario guilty mind was present but in the second case no intention of causing harm was there. The second act is categorised as self defence and is dealt under section 96 to 106 of the Indian Penal Code. In the first act the person is guilty of criminal act.