Answer:
In general, every crime involves three elements: first, the act or conduct (“actus reus”); second, the individual's mental state at the time of the act (“mens rea”); and third, the causation between the act and the effect (typically either "proximate causation" or "but-for causation").
Mens Rea refers to criminal intent. The literal translation from Latin is "guilty mind." The plural of mens rea is mentes reae. A mens rea refers to the state of mind statutorily required in order to convict a particular defendant of a particular crime. See, e.g. Staples v. United States, 511 US 600 (1994).