Ultimately, the case of William Barnes may come down to causation.

Did the bullet he shot into Philadelphia Police Officer Walter Barclay’s body in 1966 cause Barclay’s death from urinary tract and bed sore infections that went septic in 2007? Or were there several intervening events, including three car accidents and two falls out of wheelchairs, that disrupted the chain connecting Barclay’s trauma in 1966 to his death 41 years later?