The term used to refer to the body of the crime and all the elements necessary to prove that a crime has been committed is 'Corpus delicti'. This term encompasses the essential facts proving that a crime has taken place, distinguishing it from other legal concepts like 'Mens rea' (the mental state of the accused) or 'Actus reus' (the physical act of the crime). 'Habeas corpus' refers to a legal procedure that keeps the government from holding someone without showing cause. Therefore, the correct answer is 'Corpus delicti'.