It depends on who he works for. Second, most companies would do a drug test. I'm not sure if he smokes weed or does any other drugs, but one has to keep in mind, that it probably was his mistake in the first place. Plus, in my opinion it is stupid to sue your employer because somehow you got injured and cut yourself.
Also, it is a waste of time. And trust me, if you think he won't lose his job after that, then you are naive.