Feb. 4, 2009 -- In 1977 an Illinois court found Michael Evans guilty of unspeakable crimes, including murder, kidnapping, rape, deviant sexual assault and indecent liberties with a child. He was sentenced to 400 years in prison.

The conviction was based largely on a lone eyewitness identification of Evans as the perpetrator. But DNA testing subsequently proved that Evans wasn't the culprit. He was released in 2003 after serving 26 years in prison for a crime he didn't commit.

The witness later told investigators she wasn't all that certain of her identification, but was reassured when she was told there was a confession. That's according to a remarkable organization called the Innocence Project, which has used DNA evidence to help clear 232 people who were erroneously convicted of crimes they never committed.

Are these troubling cases rare? They may be only the tip of the iceberg, because DNA evidence that has proved so conclusive in cases pursued by the Innocence Project is rarely available. And false confessions, it turns out, aren't all that rare, either. They figure in at least 25 percent of the cases that have been cleared by evidence collected by the project.

Now, new research shows that a confession, even if false, can have an "astonishing" effect on witnesses who were quite sure they had picked the right criminal in a lineup. The research is part of two experiments conducted at several universities showing that false confessions can contaminate an entire court proceeding, and witnesses who are interrogated immediately after seeing a crime become more -- not less -- susceptible to later misinformation.

The research adds to a growing body of scientific literature revealing that we often don't see what we think we've seen, and even credible witnesses are vulnerabile to false testimony and harsh interrogations. It is particularly timely with the approaching trials of suspected terrorists now housed in Guantanamo Bay, Cuba, because there will likely be many confessions in connection with those cases, and some of them will almost certainly be false.

Why Confess If You're Not Guilty?

The Innocence Project cites many reasons why people sometimes confess to crimes they haven't committed, like coercion, diminished capacity, fear of violence, harmful or harsh treatment, and we must now add torture to that list. That's why any confession from someone who has been grilled behind closed doors should be treated with a great deal of suspicion.

In the first of the new studies, authored by psychologists Lisa E. Hasel of Iowa State University and Saul M. Kassin of John Jay College of Criminal Justice and published in the current issue of Psychological Science, 206 witnesses, divided into groups of two to five persons, revealed just how convincing a confession can be, even if it is untrue.

It should be noted that this was a "make believe" situation involving college students, not a real courtroom drama with lives at stake, but the researchers insist the results are consistent with other studies of actual cases.

As the participants sat in a room, a man came in, picked up a laptop computer, and walked out. He was seen by the participants for about 30 seconds. The instructor returned a few minutes later, told the students they had just witnessed a mock crime as part of an inquiry into perception. Each participant returned two days later and was asked to pick the person from a six-person photographic lineup who had "stolen" the laptop.

Of the 206 participants, 173 fingered the "thief" with varying degrees of certainty. But the person who had picked up the laptop -- the "real thief" -- wasn't even in the lineup.

That 173 people thought they had picked the real culprit is pretty startling, but the researchers called the following result "astonishing."

When the participants were told that someone had confessed to committing the "crime," a whopping 61 percent changed their identification, "in each and every case identifying the confessor" as the perpetrator.

The researchers contend that the false confession left the entire process "contaminated," because it "corrupted the evidence itself," namely the testimony of witnesses.

Memories Can Be Altered

In the second study, by psychologists Jason Chan of Iowa State University, Ayanna Thomas of Tufts University and John Bulevich of Rhode Island College, participants both young and old produced a counterintuitive finding. It would seem that sitting down with someone else and recalling an incident immediately after it happened would cement that memory, making it less likely to be altered by subsequent information.

That turned out not to be the case in this study. In separate experiments 84 undergraduate students and 60 older adults (average age 72.5) revealed a "surprising pattern," as the researchers put it. They showed "dramatically heightened susceptibility to misinformation" later if they had been interrogated immediately after the event.

"Our results provide a first look into how immediate recall affects later eyewitness suggestibility," the researchers conclude. "Contrary to the expectation that immediate recall would enhance retention of details of a witnessed event and thus reduce an eyewitness's susceptibility to misinformation, we found that immediate recall actually intensifies the misinformation effect (for both younger and older adults)."

It's not certain why that should be the case, but the researchers suggest several possibilities. It may be, for example, that subsequent information -- even if false -- causes the witness to re-examine that first interrogation and tweak the details.

"These results confirm the notion that recall not only indicates what one knows, but also changes what one knows, and sometimes these changes can have far-reaching, and perhaps negative, consequences," the researchers conclude.

As a high level federal official noted in a press conference a couple of years ago, there are things we know, and things we don't know, and things we know we don't know, and things we don't know we don't know.

And on too many days, what we don't know sends the wrong person to prison.