Two men have planned a trip across the desert and back. The day before, they tie a barrel with all the water they'll need to their donkey. They go to sleep. At 11:30 p.m. the first wife gets up and puts a small hole in the bottom of the barrel, calculating that at its rate of coming out, the men will have no water left on the way back. At 1:30 a.m. the second of the men's wife gets up. She sneaks out and poisons the water in the barrel to kill the men and goes back to sleep. Sure enough, along the trip they die. Who is guilty of murder?