This is why I can't understand why anyone would ever use a gun or a knife for murder. If you just use a car, you'll get let off. Think about this - if Martin Bryant had run over 36 people in a car, he probably would never have gone to prison either.
A conviction of murder requires the prosecution to show intent to kill. That's why most motorists can only be done for lesser charges based on proving negligence, and why Fitzpatrick got 45 years (probably subject to appeal): http://www.chicagocriticalmass.org/mcbride_trib2.html What we need is a lot less tolerance for negligent driving, not more murder charges that won't stick. My ideal solution is to apply the same testing and safety regime to driving as we do to aviation... but the economics of the motor industry and the much-cherished freedom of people to drive badly mean that this is a pipe dream. :-(