(a) A person is guilty of an attempt to commit a crime if, acting with the kind of mental state required for commission of the crime, he: (1) Intentionally engages in conduct which would constitute the crime if attendant circumstances were as he believes them to be; or (2) intentionally does or omits to do anything which, under the circumstances as he believes them to be, is an act or omission constituting a substantial step in a course of conduct planned to culminate in his commission of the crime.
(b) Conduct shall not be held to constitute a substantial step under subdivision (2) of subsection (a) of this section unless it is strongly corroborative of the actor's criminal purpose. Without negating the sufficiency of other conduct, the following, if strongly corroborative of the actor's criminal purpose, shall not be held insufficient as a matter of law: (1) Lying in wait, searching for or following the contemplated victim of the crime; (2) enticing or seeking to entice the contemplated victim of the crime to go to the place contemplated for its commission; (3) reconnoitering the place contemplated for the commission of the crime; (4) unlawful entry of a structure, vehicle or enclosure in which it is contemplated that the crime will be committed; (5) possession of materials to be employed in the commission of the crime, which are specially designed for such unlawful use or which can serve no lawful purpose of the actor under the circumstances; (6) possession, collection or fabrication of materials to be employed in the commission of the crime, at or near the place contemplated for its commission, where such possession, collection or fabrication serves no lawful purpose of the actor under the circumstances; (7) soliciting an innocent agent to engage in conduct constituting an element of the crime.
(c) When the actor's conduct would otherwise constitute an attempt under subsection (a) of this section, it shall be a 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.