Timothy Stansbury died in a New York housing project stairwell in 2004 because he startled a police officer. The officer's surprise at encountering Stansbury caused the officer's hand to clench and his weapon to fire. The death was ruled accidental by a grand jury, though the officer was later stripped of his gun for the remainder of his career. Akai Gurley died in another New York housing project stairwell last fall. A rookie officer with his finger on the trigger of his pistol tensed as he pushed open a stuck door; the added pressure on the trigger caused his weapon...