(4) Renunciation of Criminal Purpose. When the actor's conduct would otherwise constitute an attempt under Subsection (1)(b) or (1)(c) of this Section, it is an affirmative defense that he abandoned his effort to commit the crime or otherwise prevented its commission, under circumstances manifesting a complete and voluntary renunciation of his criminal purpose. The establishment of such defense does not, however, affect the liability of an accomplice who did not join in such abandonment or prevention.
Within the meaning of this Article, renunciation of criminal purpose is not voluntary if it is motivated, in whole or in part, by circumstances, not present or apparent at the inception of the actor's course of conduct, which increase the probability of detection or apprehension or which make more difficult the accomplishment of the criminal purpose. Renunciation is not complete if it is motivated by a decision to postpone the criminal conduct until a more advantageous time or to transfer the criminal effort to another but similar objective or victim.