In criminal law, concurrence refers to the simultaneous occurrence of two essential elements: the mens rea (mental state) and the actus reus (criminal act). The mens rea is the intent or knowledge that the defendant had when committing the act, while the actus reus is the physical act itself. For a criminal act to be considered a crime, both elements must be present at the same time.
For example, let's say that John is angry at his neighbor, Mike, for making too much noise. John decides to confront Mike, but during their argument, John becomes so angry that he hits Mike with a baseball bat, causing serious injuries. In this scenario, the actus reus is the physical act of hitting Mike with the baseball bat, while the mens rea is John's intent to harm Mike.
If John had only intended to scare Mike by swinging the bat near him, but accidentally hit him, then the concurrence between the mens rea and the actus reus would not be present. In this case, John would not have committed a crime because he did not have the required mental state when committing the act.
In summary, concurrence refers to the simultaneous occurrence of the mental state (mens rea) and the physical act (actus reus) in a criminal offense. Both elements must be present at the same time for a criminal act to be considered a crime.