I don't know how the law would come down (I'll let you practicing lawyers and students discuss that), but I know what I would do from a moral standpoint.
I'm interested in hearing this. I'm really not sure what I would do. I see it both ways.
I see it both ways too, but I would disclose the information. Confidentiality is a very important aspect of attorney/client relations, but when the life of an innocent human being hangs in the balance, I think there is an even more important ethical obligation. It is an age-old philosophical question of "letting die" vs. killing; perhaps you aren't the one who told the lie to put this guy on death row, and perhaps you aren't the one delivering the lethal injection, but you have the power to save an innocent life and I think you have an obligation (not legal, but moral) to do something about it. Disbar me if you want, and maybe this other guy never gets charged for the crime, but I'd never want to live with the knowledge that I allowed an innocent man to die. I could personally never look at myself the same, and my confidence in the American legal justice system would be shattered.
This situation is different than one where a defense attorney knows his client did the crime, but gets him off. In such a scenario, we as a society have decided that the burden should be on the state, and the state failed to meet their obligation or failed to follow procedure. Or perhaps the jury just flaked out (see: O.J Simpson). In that situation, I think the defense did their duty to justice and fought for their client, and the prosecution should be held accountable for letting a guilty man off the hook.
And thanks for that link, I'm reading it now. Very interesting. This is definitely a very major weakness of our system, and it is kind of scary to think about.