As the law stands, a person who accidentally kills someone can be charged with "criminal negligence". Looking up criminal negligence, it is defined "as any type of conduct that 'grossly deviates' from normal, reasonable standards of an ordinary person." So I think your example of a pure mistake does not apply. But I believe it could apply say if someone was eating while driving and killed someone. So they get not only a distracted driver fine but also a charge of criminal negligence, a felony.
As it stands now, if the victim's life is significantly impacted from injury in my example, the motorist is not charged with criminal negligence. Prozanski wants to change that.
As far as how it affects the motorist, I think they are focusing more on the victim, who now has a legal recourse beyond a civil suit (that takes lawyer money) for compensatory damages.