Three men agreed to rob a restaurant in a nearby town. Two of the men bought pistols, ski masks, and gloves for that purpose while the third man agreed to be the lookout. Prior to entering the restaurant, the man who was to be the lookout had a change of heart and wanted to call off the robbery. The other two men refused so the lookout threw down his gun and went to the nearby bus station to catch a bus back to his home. The remaining two men went into the restaurant and robbed it and its patrons. A patrol car happened by as they were leaving, and one of the men seized one of the customers as a hostage. In the exchange of gunfire with the police, a police officer and the hostage were killed. Both men escaped initially, but one of them was later captured and charged with robbery and murder. However, because of illegal police conduct in connection with his arrest and subsequent confession, all evidence connecting him with the charged crimes was suppressed and the charges dismissed. If the lookout is also arrested and charged with murder, which of the following is his stron­ gest defense?