This is what Anonymous could do after hacking a police department. Message to Minneapolis hacker.

With police records you could easily save your city from crime of many kinds. All it takes is some hidden cameras and knowledge of where and what happened. Now obviously this is illegal and you shouldn't do it but with these records you could easily find out where every domestic dispute case has happened and when it did. You could pick the most recent ones. If you were to set up listening devices/cameras you could catch it in action and potentially save a womens life. This is the kind of detective work that the NSA and FBI can only do if they have a warrant which is super complicated to obtain in most cases in the US! A small hidden motion sensored camera in their window next to the broken curtains could catch just what you were looking for or even one pointing at the door they exit/leave. Now again, I will say this is illegal and you should only do it if society collapses and the police say you can. Otherwise you cant hack PD's but if you did know of domestic disputes in your area some other way the only thing you could do is walk around their block forever and wait by the sidewalk, if you hear screams of help you could technically (legally) try to peep through the curtain cracks from the outside of the window or even press your ear up against the glass. This can only be done durring the exact moment of a possible emergency. For example if you hear a scream for help and a ton of crying you can do that and even call 911 if you want while recording evidence for them but afterwards if nothing happens and the man still controlls the women then you can't just walk up to his door and try peeping through the glass because that would be trespassing on private property for no good reason at all. You need without a doubt reasonable suspicion. Even if you hear screams it is trespassing but if a trespasser is injured on the land then the owner can be liable so there is kind of a loophole there that everything all depends on how the judge feels about you. If the judge likes you, you might get no sentencing/jailtime at all. It all depends.