To establish this affirmative defense, a defendant must prove by a preponderance of the evidence that he “voluntarily renounce[d] his criminal purpose by abandoning his effort to commit the crime or otherwise preventing its commission under circumstances manifesting a complete withdrawal of his criminal purpose.” RSA 629:1, III(a); see also State v. Jernigan, 133 N.H. 396, 398-400, 577 A.2d 1214 (1990). Moreover, the renunciation cannot be “substantially motivated by circumstances the defendant was not aware of at the inception of his conduct which increase the probability of his detection or which make more difficult the commission of the crime.