A tip for everybody - secretly film your partner saying things that might incriminate him/her later if it ever comes to a court case.
For example ask loaded questions like "Would you lie about me in court?", then if he/she says "You bet I would!", you can play the footage to the judge and jury later..
Oh, and keep old letters, texts, emails and phone messages from them too because you never know when you're going to need them as evidence.
For example I've got a letter from an old ladyfriend in which she says (among other things) that she likes "being naughty" with me. So that could be used against her in court if I ever have to, it's called "insurance"..
PS- I once secretly recorded the caretaking staff at an apartment block where i used to live because they were treating us tenants bad, and the council sacked the lot of 'em on the strength of my recording..