I've read that Google's position on liability is that it should be on the maker of the autonomous car, which makes perfect sense to me. Traffic accidents (including with pedestrians) rarely involve criminal culpability anyway, except when alcohol or drugs are involved, or when there's clear evidence of gross negligence, so it's really a question of civil liability. Putting that liability on the maker of the machine aligns the interests correctly and ensures that the liability is well-funded.

So, I really don't think it's as much of a problem as you think it is.