Everybody agrees that attorney-client privilege is a good thing. Suspects would never trust lawyers who occasionally ran down the hall shouting “He did it! He told me himself!”

The privilege – which demands that attorneys keep their clients’ confidences – helps keep the justice in the criminal justice system. But how about when it perpetuates a shocking injustice?

Just that appears to have happened in Chicago over the last 26 years. In 1982, Alton Logan was convicted of murdering a security guard at a McDonald’s restaurant and was sentenced to life in prison. About the same time, another man, Andrew Wilson, was facing a possible death penalty for murdering two police officers.

But one of Logan’s supposed accomplices told his public defender that he’d never seen Logan before – not only that, he said that Wilson had actually killed the guard. That attorney told Wilson’s public defenders, W. Jamie Kunz and Dale Coventry. They pressed Wilson, and he admitted he’d killed the guard.

The dilemma: Kunz and Coventry couldn’t tell anyone of that admission – which could have cleared Logan – without betraying their own client’s confidence. And Wilson, who was already facing the death penalty, wasn’t about to cop to a third murder.

So – honoring attorney-client privilege – Kunz and Coventry stayed mum until Wilson died in prison. In the meantime, the apparently innocent Logan did 26 long years behind bars.

Just about any public defender would probably have a hard time sitting on a secret that could exonerate a wrongly convicted man – especially for the sake of protecting a murderer’s privileged admission. Kunz and Coventry appear to have hunted high and low – conferring with scholars, ethicists and the bar association – for some way to pass on what they knew about their client.

This is a case in which attorney-client privilege, meant to preserve justice, instead produced a travesty of justice.

There’s a saying: Hard cases make bad law. This hard case might suggest that attorney-client privilege ought to be done away with, or at least have large exceptions carved out of it. But how do you do that without leaving defendants unwilling to confide in the attorneys who are supposed to represent them and them alone – not some other defendant down the cell block? Without that confidence, there’s no real defense; without a real defense, there’s no fair trial.

A public defender does have what might be called the kamikaze option. Let personal ethics trump legal ethics: Violate the privilege, betray the secret and take the consequences from the bar association.

It might end your career and create a small tremor in the justice system. It also might make it easier to face yourself in the mirror the rest of your life.