Drunk driving and muder are very serious crimes. If someone has killed someone else because of intoxication, it's important to make sure they can never do it again. A life sentence will not only keep offenders from repeating, but it will send a strong message to communities that the government is tough on crime.
If the pedestrian was jay walking, then it's the pedestrians fault. Many pedestrians who are killed by motor vehicles are under the influence themselves. Usually, speeding or another moving violation in addition to the alcohol causes accidents. We should pay more attention to these other "minor" traffic violations and punish more harshly.
I never understood why pedestrians have right of way anyways. Not only do they waste drivers time but they also put themselves in danger 90% of the time by abusing that right. They should have to wait until traffic has passed or until the road is fully clear to go. Cars are made to be driven not to wait for pedestrians.