Comment by AnIrishDuck

I hate to break it to you, but you are currently still responsible for killing somebody while driving a car on cruise control, especially if you act recklessly.

EDIT: to be less snarky, there are obvious exceptions if a manufacturer defect is involved. But I still imagine it turns on things like foreseeability and proximate cause (IANAL). Nevertheless, if you were asleep at the wheel, you're getting held responsible.