I think they should be punished as murderers. I don't think drunk driving should be illegal, though.
So, if the cops had caught him, for instance for swerving into the other lane, and pulled him over, gaining the chance to save the passenger's life, they should have had no authority beyond perhaps giving him a ticket for the swerving and then telling him to drive carefully? We shouldn't have laws to protect against the introduction of clearly, demonstrably dangerous conditions?