Is it really illegal if you take someone else's drink and...?
Is it really considered drugging someone if you took their drink and they angrily left, then they come back and angrily drink their drink in front of you to piss you off, and you spiked it while they were gone? I feel that if they inflicted it onto themselves, it's not your fault since they acted on impulse.
Also if you poison someone's drink in the same manner and they drink it in the same manner, it's not murder if they die, it's suicide.