Several years ago an acquaintance in England was assaulted by two thugs trying to rob him (he resisted), one with a knife, one with a razor blade. He ended up having around five hundred stitches. In the struggle he managed to stab one of the thugs in the leg with the knife while it was still in the thugs hand. He ended up being tried (and acquitted) for assaulting the robber. Really a deterrent to crime.