(1) In any prosecution for criminal attempt to commit a crime, it is a defense that, under circumstances manifesting a voluntary and complete renunciation of his criminal purpose, the defendant abandoned his effort to commit the crime and, if mere abandonment was insufficient to avoid the commission of the crime, took the necessary affirmative steps to prevent its commission.
(2) A renunciation is not "voluntary and complete" within the meaning of this section if it is motivated in whole or in part by:
(a) A belief that circumstances exist which pose a particular threat of apprehension or detection of the accused or another participant in the criminal enterprise or which render more difficult the accomplishment of the criminal purpose; or (b) A decision to postpone the criminal conduct until another time or to transfer the criminal effort to another victim or another but similar object.