retroguy:
I've had this situation before, and I can tell you - if you can possibly manage it, the best solution is to move.
You can complain all you like, you can collect as much proof of misbehaviour as you want, you can follow the process to the bitter end.
When you are through, you will not believe how many "rights" miscreants have, and how few you seem to have as a law-abiding complainant. People who engage in annoying or troubling behaviour seem to have radar for how far they can go and stay within the law. You'll call the police time after time after time and the answer will usually be that the situation isn't "serious enough" to warrant their doing anything. On those rare occasions the misbehaviour is serious enough to have broken a law, the perp will apologise in court, or pay a small fine, or make some minimal amends like a fast cleanup of neglected property, and will go right back to annoying the crap out of you. Only now they'll do it with a smirk on their face, because you called the law on them and nothing much happened.
Again, move if you can. What you spend on relocation, you'll save on bills for therapy, Paxil, dentistry to restore the enamel ground off your teeth, and legal services. Trust me.
If you cannot manage that, the best proof of a problem is videotape, and the next best is pictures on actual film (not digital). Courts respond best when they can see evidence that comes in a form that is not easily edited. Digital photos and tape recordings are both pretty easy to tamper with, and judges know that.