Criminal intent. The state of mind indicating culpability which is required by statute as an element of a crime. See, e.g. Staples v. United States, 511 US 600 (1994). However, for strict liability crimes, state of mind as to at least one element of the crime is irrelevant.
Mens rea
Believing that murder is an art and in carrying it out successfully they will prove themselves "superior beings", Brandon and Phillip intentionally strangle their former classmate Dennis with a rope. The actus reus is the act of strangulation- that is putting the rope around the neck of Dennis and cutting off the circulation of blood to his brain until he is dead. The mens rea refers to the guilty mental state of the two men. In this case, mens rea is the men's intentional wish to bring about the death of Dennis as they strangle him.