Here's a suggestion of a particularly violent case:
A Cry for Help: The Tracey Thurman Story (1989 TV movie) starring Nancy McKeon, Dale Midkiff and Graham Jarvis
IMDb synopsis: Tracy Thurman was married to a man who abused her, but he continues to harass her even after she gets a restraining order. The police do little to help. When he brutally beats her, stomps on her head and slashes her throat in front of police officer who does nothing to stop the savage attack, she sues the city and the police department for failing to protect her.
I've been answering many questions at the site the other person suggests, very likely several hundred movie mysteries.