When exactly did the word "mistake" become synonymous with the word "crime"?
A mistake is something that happens when you are not attentive or careful enough. When you discover it, you correct it or apologize for it. How does someone imprison a mortally wounded man, enlist others to dump his corpse, clean up the evidence and burn the seat, then sit on the dirty little affair for four years by mistake?!
As far as her character is concerned, how do you judge the content of a woman's soul if not by her actions? Anybody can blubber in front of a camera when their fate hangs by the judgment of strangers, but how remorseful was she the day before she got caught. Character happens when you think no one's looking.