Mens Rea and Actus Reus

To obtain a criminal conviction, the prosecution must establish the presence of two elements at the time of the crime—namely, actus reus (“guilty act”) and mens rea (“guilty mind”). A failure to show the presence of these elements will lead to an unconditional acquittal of the charged crime. Because both must be proven with evidence beyond a reasonable doubt by the prosecution at trial, the argument that there was no actus reus or mens rea is not a defense per se. They are unlike various affirmative defenses, such as the insanity defense or selfdefense, which are viewed as excuses or justifications for otherwise disfavored conduct.