We're dealing here," said Vimes, "With a twisted mind.""Oh, no! You think so?""Yes.""But... no... you can't be right. Because Nobby was with us all the time.""Not Nobby," said Vimes testily. "Whatever he might do to a dragon, I doubt if he'd make it explode. There's stranger people in this world than Corporal Nobbs, my lad."Carrot's expression slid into a rictus of intrigued horror."Gosh," he said.

Murder was in fact a fairly uncommon event in Ankh-Morpork, but there were a lot of suicides. Walking in the night-time alleyways of The Shades was suicide. Asking for a short in a dwarf bar was suicide. Saying 'Got rocks in your head?' to a troll was suicide. You could commit suicide very easily, if you weren't careful.