What is the scope of the withdrawal defense in the context of a conspiracy?

In addition to being a crime in itself, conspiracy also determines the scope of a defendant's criminal liability for substantive offenses committed in furtherance of a conspiracy. A defendant is criminally liable for any underlying substantive offenses committed by co-conspirators during the defendant's membership in the conspiracy. On the other hand, a defendant cannot be held liable for substantive offenses committed before joining or after withdrawing from a conspiracy. Levine v. United States, 383 U.S. 265, 266, 86 S.Ct. 925, 925, 15 L.Ed.2d 737 (1966). In this context, therefore, the withdrawal defense also limits liability for underlying substantive offenses.