What is actus reus and mens rea?

Every crime (with a few exceptions) has the elements of actus reus (“guilty act”) which means the act of committing the crime (for example the act of stabbing someone in the case of murder) and mens rea (“guilty mind”) which means the “relevant intention” of the offender. “Relevant intention”  taps into the conscience of the offender. For example, in the case of ‘murder’, the offender must “intend to kill or seriously harm the victim”, and in the case of theft, the offender must “intend to permanently deprive the victim of their property”. To put it simply, the offender must have ‘really meant’ to commit whatever crime he is accused of. If the prosecution does not prove that the offender ‘really meant it’ but that he did commit the act, a defence may be considered. For example, if person A kills person B but he did not legally intend to kill person B, he will not be guilty of murder, but may be guilty of manslaughter (‘homicide with a reduced intention’) or another offence which carries a smaller penalty (for example a limited term of years and not life imprisonment).