I'd have to turn them in, right is right and I couldn't in good conscience let an innocent person be in prison for something that I knew they didn't do....family or no family.
You witness a terrible crime, committed by your mother or best friend or any relative. You know its a 25+ prison term. You also know the police arrested an innocent person, but you don't like the person, what would you really do?
In the words of Yul Brynner, that's a puzzlement.
I doubt if it's possible (for me) to answer without a specific crime in mind. Obviously it has to be a doozy to be worth 25 years free accommodation but, as Cookie pointed out, sometimes that's the only course of action to take.
Of course, if the innocent-presumed-guilty party was one of a couple of politicians I can think of I might be tempted to keep my mouth shut.
I couldn't live with myself, if I didn't turn my relative in. I could not see an innocent person being prosecuted and going to jail over something they didn't do.
A crime that bad ... Probably a reward for information ... So definitely turn them in. Also, they were stupid enough to either tell me they did it, or leave me as a witness ... Another reason to turn them in.
I would turn them in. I would assume if someone did something that bad once they will do it a second time.