Killer Ex-Wife or Self-Defense?

Killer Ex-Wife or Self-Defense?

Available on A&E Crime Central, Philo, Prime Video, Tubi TV, Disney+, Hulu, Sling TV, A&E
S2 E3: When a man is shot dead in rural Montana, his ex-wife is accused of murder. She says that she shot him in self-defense after an assault--but with forensic evidence revealing a shot to the back of the head, what is the truth?