Prisoner advocacy group The Innocence Project has used D.N.A. to overturn the wrongful convictions of 266 people since 1989. In twenty-five percent of those cases, the D.N.A. exoneration was an extreme surprise—not because the people had been convicted, but because they had confessed. Why would anyone do that if they were innocent? ... Because it doesn't make rational sense of them to lie about their guilt, their behavior lends weight to their confessions and makes it harder for them to prove their innocence later. Now Iowa State University researchers are trying to understand what causes these false admissions of guilt.