The process of injecting the venom does require the wasp to be alive, so once it's dead there's no risk of accidentally poisoning yourself on the stinger. There may be some residue left but that wouldn't be enough for any noticable effects.
However, unless the wasp stung someone many many times prior to death there should still be some venom left that would hold the same effects should it be extracted and digested/injected by other means.