I'd go as far as I was able to go (as long as it didn't involve breaking any laws or harming my own family), because I have seen, for myself, how easy it for a person to be "railroaded" simply by having a few "non-System" people offer bad information, have a few System people make mistakes as a result of it (and then not be willing to own up for a number of reasons), and then have all those who made the mess in an innocent person's life dig in their heels because the longer it goes on, the more damage and loss they're responsible for.
My own situation has nothing do with breaking any laws or criminal matters, but seeing what has gone on has been horrifying and life-destroying. Worse, since anyone not involved with the situation quite reasonably doesn't know what happened, and doesn't want to get involved, that can leave someone innocent left entirely alone and without having anyone who will stand up for him.
If I were sure the person was innocent I'd do whatever it took (within the limits of what I said above) to clear his name. If I wasn't entirely sure but sure got the feeling that everything he said seemed to make sense, I'd ask him for additional information or back-up to his story in order to see if I could get a better reading (and I think, most of the time, all it takes to get "a better reading" is bothering to pay attention to the person's story and then, if necessary, asking for a little more common sense information or story.
When all is said and done, it's most often the old, "It's not my job," "It's not my business," and "I can't get involved with what isn't my business," kind of thinking that leaves innocent people without justice.
What may be the most sickening thing about the "it's not my job" kind of thinking is that it can so often be the very people who have stood up for any number of other people who find that when they need someone to stand up for them there is nobody. Human nature is a "lovely" thing, isn't.... (and that, in case it didn't come through correctly) was sarcasm). As anyone can see, this is a real sore spot for me. That's what happens when you have been "accused" of being something (even if not a criminal) that you're not and waiting twenty years to have someone get to the truth so you can have your "regular" life back.
It's so easy to whip up a few lies about someone, leaving that person to try to prove a negative.