Katie and Jimmy seem to be a perfect young couple, but after their first child was born, he started being abusive to her and neglecting her.
Then when she gets pregnant again, things get completely out of control.
When Katie finally decides to leave, Jimmy beats her and waves a rifle in her face, basically telling her "it's you or me".
Katie winds up killing him and is arrested and put on trial.
However, during all that time, Katie was hiding the abuse from her family, friends, and authorities, one, in hopes that her still-devoted love to Jimmy would eventually persuade him to stop abusing her, and two, to keep her police officer father (with his own marital issues) from meddling in her life.
Unfortunately, this lack of past evidence throws quite a few speed-bumps in the road towards an acquittal for self-defense reasons.