When my friend was murdered(his dad attacked him, he fought back, and his dad shot him.) The cops knew his dad was a violent alcoholic, and that his son was trying to move out.

Except the dad was the only witness, and despite many people's statements about abuse and alcoholism in the household it was declared self defense due to "lack of evidence." He's free to walk around continuing to drink himself to death. Piece of shit.

My point is sometimes they don't even solve it correctly when the killer is standing right there.

The legal system is a fucking joke.