I wonder how many years in prison would get you shooting someone like that in self defense.
Good thing guns are illegal, eh? https://notthebee.com/article/145-people-stabbed-with-syringes-with-unknown-substance-during-france-music-festival
Discussion
Should be 0, that would not even be an escalation of force from the perspective of the victim, not knowing what's in the syringe.
Likely none. That could as easily be cynaide or ricin as ebola or aids. US courts would free the fuck out of that defendant. As long as they weren't in a New York court.