It is a very big deal, had there been an actual premeditated intention. There has to be a clear mind deciding that.

If you do not criminalize using influential substances themselves, this argument is futile. You say the moment you hit the bottle, you've decided to kill someone. Well, make that a crime. Drinking or using drugs should be a crime. If you can't criminalize that, charging someone under influence sounds like charging a down syndrome person with murder.

And then we all know how the Prohibition turned out. Oh, the perks of enjoying certain freedoms always comes with some costs. These stuff are criminalized here, still a friend of mine got his car totaled by a drunk driver. Drinking itself has 80 lashes here. Not sure how it went for that drunk driver though. Legal system here is 1000 times worse than what you've got over there.