That depends. Are we talking about a thief who was accidentally killed in a brawl with the property owner (or the troublesome death-by-glitter scenario that some in this thread are so concerned about)? Or a property owner who subdues, binds, and executes the thief? I'm open to arguments that it should be illegal to use lethal force against thieves when it's 100% clear that the thief poses no physical danger to the victim. I also believe that the property owner generally bears responsibility if their traps or other defenses are mistakenly employed against an innocent party. But in general, any injuries a thief incurs during a theft should be his own responsibility, and I'm okay with a world in which thieves live in fear of committing thefts.