yes,im wondering if it would be legal in a situation like this to solder razor blades to your possesions on a persons vehicle in such a way that only bad guys get cut
The short answer is no, it is not legal.
pioneer, from I remember of my law studies, you cannot 'booby trap' things. We had this discussion come up during property law discussions. If it happened that there was a sharp edge on some hard to reach place, through no fault of yours, only reachable by someone trying to remove your stereo or what have you improperly, the odds are in your favor if they are injured while trying to steal it. If you stick sharp bits in there designed to injure, you're stacking the deck against yourself in court when they sue. It might be a crime regardless.