alt Hacker NewsUnfortunately you are responsible for making sure your plates are clearly visible while driving. Mud doesn't easily coat your plate to the point of obscurity, you either were driving in lots of heavy mud (clean off car before going back on public roads) or haven't cleaned accumulated mud off in a while (not adhering to making sure your car is road legal).
Negligence will still get you in trouble.
Yes, but it will usually get you into less trouble than if you did it deliberately. That's why almost every jurisdiction has a distinction between murder and manslaughter (and often first and second degree murder). There isn't just a "caused someone else to die" crime and everyone that does that gets exactly the same punishment.