Accident's happen but in today's legal world, it isn't about justice. Prosecutors are looking to get a conviction at all costs.
I think it is about justice. Yes accidents happen, but you are legally and morally responsible to maintina total control of your vehicle at all times while driving. Looking in your mirror while driving to see if you have strep (like you could actually tell) is dumb. The techincal term for this is negligent homicide, somebody died because he wasn't paying attention, that's a bad thing.