John, Fred, and you decide to rob a bank. You gather together weapons, draw up a plan, and steal a getaway car. On the way to the bank, you begin to regret your decision. You tell Fred and John, "Listen guys, best of luck on the bank robbery, but I'm out." John, the driver, drops you off a few blocks from the bank. Things don't go well during the bank robbery and John and Fred are caught and implicate you in the crime. At trial, you raise the defense of withdrawal. After all, you didn't even help rob the bank. Is the defense of withdrawal valid? What are the elements of the defense of withdrawal? What would have to happen to make the defense valid, if anything?