How to pick up proofs (legally)?

I've got problems with trolls for my childhood because I've problems with my family (where's a lot of police officers) and their friends including neo-nazis and whoever else (all protected by the police from my family). I moved to a different country (the UK), don't speak to them for long years and it still continues because they're trolling wherever they can (even in front of me) since the email can be sent around the world and here's a lot of Slovaks from my city. I can know because I accidentally met two of them walking from 2 shops where I worked at the same time when they visited it (they saw me, played to be confused, and left). All their arguments are ad hominem. It usually starts with a game on a good and bad policeman where the bad play a savor of the society and the good is supposed to be my savor, so the actors of good (my family) get talking people those should normally stay behind me. They use brutally emotional speech, then later, they troll in a form of questions like 'Is it true that *** because all people said (in reality, none except my family and their friends says)', we just wanna know what's the truth now, it's good for him if he changed and you say, you help him, right? We just want to ask something.

I'm a programmer and, with Wikipedia, etc even non-programming kids are able to hack someone or pick up the proofs in a different illegal way, but it doesn't help in a court. I don't have people willing to show up their face in a court and risk their own lives because of me. Any advice?