This story was originally broadcast on March 9, 2008. It was updated on May 23, 2008.

This is a story about an innocent man who languished in prison for 26 years while two attorneys who knew he was innocent stayed silent. As correspondent Bob Simon reported earlier this year, they did so because they felt they had no choice.

Alton Logan was convicted of killing a security guard at a McDonald's in Chicago in 1982. Police arrested him after a tip and got three eyewitnesses to identify him. Logan, his mother and brother all testified he was at home asleep when the murder occurred. But a jury found him guilty of first degree murder.

Now new evidence reveals that Logan did not commit that murder, something that was not new to those two attorneys, who knew it all along but say they couldn't speak out until now.

Alton Logan's story cuts to the core of America's justice system.

Simon met Alton Logan in prison, where he's spent almost half of his life.

Asked if he still counts the months and days, Logan told Simon, "There's no need to count the months and the days. Just count the years."

Logan said that during the first five or six years he was "consumed" by anger. "Then I come to the realization that 'Why be angry over something you can't control?'"

Logan, who maintains he didn't commit the murder, thought they were "crazy" when he was arrested for the crime.

Attorneys Dale Coventry and Jamie Kunz knew Logan had good reason to think that, because they knew he was innocent. And they knew that because their client, Andrew Wilson, who they were defending for killing two policemen, confessed to them that he had also killed the security guard at McDonald's - the crime Logan was charged with.

"We got information that Wilson was the guy and not Alton Logan. So we went over to the jail immediately almost and said, 'Is that true? Was that you?' And he said, 'Yep it was me,'" Kunz recalled.

"He just about hugged himself and smiled. I mean he was kind of gleeful about it. It was a very strange response," Kunz said, recalling how Wilson had reacted.

"How did you interpret that response?" Simon asked.

"That it was true and that he was tickled pink," Kunz said.

"He was pleased that the wrong guy had been charged. It was like a game and he'd gotten away with something. But there was just no doubt whatsoever that it was true. I mean I said, 'It was you with the shotgun-you killed the guy?' And he said, 'Yes,' and then he giggled," Coventry added.

The problem was the killer was their client. So, legally, they had to keep his secret even though an innocent man was about to be tried for murder.

"I know a lot of people who would say, 'Hey if the guy's innocent you've got to say so. You can't let him rot because of that,'" Simon remarked.

"Well, the vast majority of the public apparently believes that, but if you check with attorneys or ethics committees or you know anybody who knows the rules of conduct for attorneys, it's very, very clear-it's not morally clear-but we're in a position to where we have to maintain client confidentiality, just as a priest would or a doctor would. It's just a requirement of the law. The system wouldn't work without it," Coventry explained.

So that was the dilemma. They couldn't speak out, they felt, but how could they remain silent?