If you kill somebody by purposefully driving into them, even if the prosecutors can't prove whether you intended them to die or just be severely injured: Murder.
If you _try_ to kill somebody with your car but you fail: Attempted Murder.
If you were just trying to "scare" them, or if you weren't on a road at all and they died "by mistake": Manslaughter
If you inadvertently kill somebody while driving drunk: Causing Death by Careless Driving while Under the Influence of drink or drugs
If you were so very bad at driving that it should have been obvious that you might kill someone: Causing Death by Dangerous Driving or Gross Negligence Manslaughter.
If you were just bad at driving: Causing Death by Careless Driving.
Of course if your husband is an American spook you can just lie and then hurry aboard a flight home before anybody realises where you went...