Testimony from informants has played a role in 15% of the convictions overturned nationwide by DNA evidence, according to the Innocence Project. In a 2005 study, Northwestern University Law School's Center on Wrongful Convictions documented 38 cases in which informant testimony sent innocent men to death row.
The issue with informants is partly one of motive. Why are they testifying? Street informants often are seeking financial rewards or trying to avoid arrest. Jailhouse informants usually are motivated by a reduction in sentence or other special favors.
Prosecutors are not permitted to offer inmates favors in exchange for testimony. But in this case, one inmate mentioned his assistance in the McCullough case in court papers seeking a reduction in his sentence. And another did receive what the defense contends was favorable treatment: He was allowed to testify anonymously as "John Doe." His name, his record and other details about his background remain sealed from the public record.
Campbell said he found the jailhouse informants credible because they told three different stories about how Maria died. Police couldn't have planted the stories the inmates told.
"What you get from this is there was no effort by us to go over there and hang out some cheese, and so whoever gives us the story gets the cheese," he said.
Faulty eyewitness identification is also problematic, according to the Innocence Project. In Illinois, it has played a role in 24 wrongful convictions, cases later exonerated by DNA evidence. Among the factors contributing to misidentification, research shows, is the kind of photo lineup used, and the way it is administered by police.
The defense contends that Kathy Chapman chose McCullough's photo from an "impermissibly suggestive" lineup. His was the only photo with a dark background; he was the only one not wearing a suit; the others looked off to the right, but he stared directly into the camera; the others' hair was combed while his was unruly; the other photos were yearbook photos, his was not.
"The picture of Jack was done differently, no tie and the lighting is different, and that's the one she picked," defense attorney McCulloch said. "It shouldn't be a surprise, but 55 years later maybe people react to subliminal suggestion. If you're looking for 'one of these things is not like the other,' then the answer is pretty clear which photo to pick."
The defense also notes that investigator Hanley spoke with Chapman for about 90 minutes before returning more than a week later to show her the photos.
Unlike Illinois, many states do not allow the same investigator who questions witnesses to show them photographs of suspects. The point is to avoid the natural tendency of witnesses to give the answers they think police want to hear.
Campbell is certain that Jack McCullough killed Maria Ridulph. He is confident in Kathy's Chapman's identification of "Johnny." He and Hanley note that she did not learn she'd chosen McCullough's photo until 10 months later, when he was charged. Campbell believes her when she says she could never forget his face.
"I spent a lot of time with her," he said. "I am familiar with the identification problems, and snitches have taken down clients of mine before. At the end of the day, it's the best system we have."
However problematic they might be, the testimony from the jailhouse informants and Kathy Chapman's eyewitness identification convinced Judge Hallock that McCullough was a child murderer and a kidnapper. He expressed confidence that his decision will be upheld on appeal.
Defense attorney McCulloch and his investigator, Harrolle, remain convinced that their client is innocent.
"I think it was an incredibly thin case," said McCulloch. "It seems to me Illinois has a bad history of having existing prosecutors file sensational cases as they prepare for election."
If Campbell pursued the 55-year-old cold case as a means to re-election, it certainly backfired. The prosecutor lost his job by 700 votes just weeks after the conviction. He will be watching the appeal as a private criminal defense attorney.
He is keenly aware of the questions that swirl around many cases after a conviction -- especially a cold case.
"Any type of cold case is going to raise questions, and to be honest with you, I think that's healthy," Campbell says.
He cites a sad truth about the criminal justice system: It is fallible.
"Here in Illinois, we've had a lot of people go on death row who ultimately ended up being innocent," he says. "We're always concerned about people being convicted of crimes they didn't commit."
'Look in the box'
Jack McCullough finally got his say at his sentencing. He stood before the court last December 10 -- 55 years and seven days after Maria Ridulph disappeared.
He used the occasion to tell his version of the truth. He insisted that he didn't kill Maria, and that the FBI had cleared him. He blamed his legal predicament on ambitious cops, corrupt prosecutors, an incompetent judge and spiteful siblings. He challenged Kathy Chapman's ability to remember a face after 55 years.
He accused the judge of ignoring the FBI reports and his alibi. "Look inside the box," he exhorted, pointing to a carton labeled "McCullough case" resting on the defense table. "The truth is in the box."
He was defiant to the end. His remarks to his probation officer were read aloud at his sentencing. Asked what caused him stress, he had said: "Corruption, Democrats, socialism, rude people, noisy people, black people and Muslims."