Vigilante justice is the only answer.
I've spent a lifetime seeing crims get away with pretty much everything due to recalcitrant plod or worse, lawyers. Very few people get arrested by real plod for anything more than a 'suspected' crime, so the whole,"He wasn't guilty yet" argument is moot. That's why people go to court dont-cha-know. The police don't try them although that does seem to be changing... So quit it with your "They didn't know for sure he was guilty and blah..." - that describes pretty much every arrest in Britain.
As a few people above have pointed out: What will these guys do next time? They'll just beat the snot out of a caught crim. I've seen enough in my time to do the same now. I'm tempted to put a sign up on my house that says: "This house doesn't call the police." - because I know if I do call the police they won't come, not for anything, not for any crime, they can't be arsed. And even if they did come out, they'd find a way of punishing me more than the crim, or they'd let the crim off with some meaningless fine or community service, yet the next time an 80 year-old woman refuses to pay her Poll/Council Tax, they'll be 'round there in force, throwing her in jail. Or God forbid you watch some pr0n or don't pay your TV licence or horror of horrors...SPEED!
If I encounter any kind of criminal in my life I will deck first, ask questions later. There's really no reason not to. What's the alternative? Go through normal channels and hope the police and the justice systems works!? If you believe that, then you must have been asleep for the last 20 years.
It's also interesting in that this draws a parallel with that old biddy on the train platform a few months ago who had a go at a couple of blokes for smoking, a couple of times too. They ended up throwing her off the platfom onto the train tracks and she broke her wrist or something like that. It's odd how there was wide-spread condemnation of the 'thugs' and wide-spread support for the biddy. But really, that too is taking the law into your own hands. There are railway staff and police trained to deal with those situations, trained and authorised to enforce the 'vital' (cough) 'no smoking law' in our public places - then surely if the woman acted out on her own cognisance and confronted the men, she took the law into her own hands and thus must bear at least some of the responsibility for what happened next, i.e. getting hoiked off the paltform. They were only smoking ffs. Interesting to see what kind of porridge they're doing now though...for their crime: Smoking.
You can't have it both ways.
Just to clarify, I think Tony Martin should've been given a fucking medal for shooting that burglar and I think that as the police are generally absent nowadays in most crimes, there's very little choice but for the public to take the law into their own hands, and mistakes will happen but hey, least we won't shoot anyone dead in our zeal...hmm?
You can't advocate the police and the justice system as "The Right Thing To Do" or "The Answer", when they can't be bothered to participate or, when they do, they capitulate on the side of the criminals, i.e. the thief who fell through a warehouse roof in Liverpool and got compensation for the roof being weak, bless him. You're naive in the extreme if you think that solves these kind of issues.