Criminal Liability

At common law, definition of crime consists of two main elements mens rea and actus reus. Together, they describe the crime committed. A guilty behavior manifests itself in some form of "act" (commission), or "failure to act" (omission).

In order to have criminal liability, there must be criminal conduct. A criminal conduct is conduct that is without justification and without excuse. Voluntary act is the "conduct" part of the criminal conduct. It is worth noting that many crimes do not carry a criminal intent or bad result, but only rarely does a crime not require a criminal act.

Crime

According to oxford dictionary, a crime is an action or an omission constituting an offence that is punishable by law.

Offense

According to Oxford dictionary, an offence is a breach of a law or rule. It is also an illegal act.

Mens Rea (Criminal Intent)

Mens Rea refers to criminal intent. The literal translation from Latin is "guilty mind." A mens rea​ refers to the state of mind statutorily required in order to convict a particular defendant of a particular crime. 

Establishing the mens rea of an offender is usually necessary to prove guilt in a criminal trial. The prosecution typically must prove beyond reasonable doubt that the defendant committed the offense with intent.

Actus Reus (Criminal Act)

This could be understood as the criminal act (voluntary body movement) triggered by the criminal intent. Actus reus refers to the act or omission that comprise the physical elements of a crime as required by statute.

To prove beyond any reasonable doubt and secure a conviction, both Actus Reus and Mens Rea need to be shown.

Concurrence

The requirement that the criminal intent triggered the criminal act.

Conduct crimes

Conduct crimes are those which require a criminal act triggered by criminal intent e.g Burglary. The elements of conduct crime are:

1. Corpus delicti - This is the "body of crime". It doesn't necessarily mean a physical body. It refers, instead to the elements of a crime
2. Criminal conduct (actus reus) - criminal act triggered by the criminal intent (mens rea)
3. Criminal act - voluntary bodily movement.
4. Criminal intent (mens rea) - this is the criminal intent

Bad result crimes

The criminal act causing criminal harm e.g Homicide. The elements of bad result criminal liability are:

1. Voluntary act - actus reus
2. Mental element - mens rea
3. Circumstance element
4. Causation element
5. Harm

Sources

1. Legal Information Institute - Actus Reus
2. Legal Information Institute - Mens Rea
3. Criminal Liability