If you put Mary should not get away with the crime, for the first reason, you could write that Mary didn't really have a good reason to kill her husband. Next, you could say that her husband did say she would be looked after, and taken care of. Last, Mary didn't show any mercy, I guess.
But if you put Mary should get away with the crime, then you could write she was kind to her husband ( before the murder) because she was devoted to being a housewife, next, she was having a child, and last because her husband was so snotty. I hope this helps.
