(1) A person shall not be punished for an attempt if he voluntarily
abandons the further execution of his criminal scheme or prevents
its completion. If, quite apart from anything done by the abandoning
party, the crime is not completed, no punishment shall be imposed
on him if he voluntarily and earnestly endeavored to prevent its
completion.
(2) Where several persons participate in an offense, no punishment
for an attempt shall be imposed on whomsoever voluntarily prevents
its completion. Nor will punishment be imposed on any person
who, through his voluntary and earnest endeavors, attempts to
prevent the commission of the offense, if it was not completed
for other reasons, or if it was completed quite independently
of his antecedent conduct.