Withdrawal from conspiracy is a defense when a person to conspiracy changes his/her mind and withdraws from that conspiracy before anyone commits an overt act. The person who withdraws from conspiracy must have taken affirmative action to defeat the purpose of the conspiracy. When a person withdraws from conspiracy before an overt act, s/he cannot be convicted since the crime is not complete at that time. Conspiracy becomes a crime when there is an agreement and performance of some overt act by one of the conspirators.
In United States v. Read, the Seventh Circuit held that the defendant in a criminal conspiracy prosecution cannot constitutionally be required to bear the burden of proving his withdrawal [United States v. Read, 658 F.2d 1225 (7th Cir. Ill. 1981)].