Extreme Honesty = innocent man in prison for 26years.

the attorneys' ability to act on their knowledge to a great deal depends on exactly when they received the confession -- but usually there isn't a thing they can do without losing their livelihoods - for the reasons already mentioned here. Anybody involved in criminal defense is going to run into a situation like this probably at least once. The only time they are clear to act is if they're informed that their client is engaging right then in an illegal activity, or planning to execute a crime. Then they are actually required to act.

Sometimes an attorney will try to get the information out "into the street" in some way that can't be connected with them, and just hope that somebody picks up on that information; or they might try to get some other informant to go to the police with the tip, but that is much more dangerous for the attorneys. It's a real quandary. The ethics involved in providing a defense can definitely conflict with ethics at large -- but so can the very idea of providing a defense for every accused in the first place.

You can let the ethics committee know this is the situation but they're there to enforce the bar association rules -- and the rules are, keep your mouth shut.

And people stuck in this situation will rationalize to themselves that a confession is not proof of guilt. And really, it isn't.

This is why defense attorneys don't ask people if they're guilty and will usually cut them off if the client tries to tell them on their own. They need to not know -- because if they do know the person is guilty, it restricts the kinds of things they can do to defend them. Though it doesn't prohibit defending them.