Formostcrimes, you must have a criminal act (Actus Reus) coupled with a criminal state of mind (Mens Rea). I cannot be arrested simply for thinking that I want to kill my wife. Spotting the criminal act on an exam is usually fairly easy. However, sometimes the "act" can be the failure to act. The failure to act can be a crime when a person has a duty to act. List a failure to act that could be a crime and explain why it should or should not be a crime.