Acting together

Two partners plan to rob a bank. The first recruits a driver while the second purchases a shotgun from a gun dealer. The driver knows he’s taking part in a robbery, although not a bank robbery. The gun dealer should have checked his customer’s police record before the sale, but failed to do so. The bank is robbed, a guard is killed, and the robbers escape, only to be caught later. “They committed bank robbery,” a prosecutor will say. But does “they” include the gun dealer, whose lax standards made the robbery possible? “They conspired to rob the bank”—but does “they” here include the driver, who didn’t know it was a bank they were robbing? “They killed a bank guard”—but does it matter which robber inside the bank pulled the trigger?