Police arrested John Mark Karr on Wednesday in connection with the murder of JonBenet Ramsey. Karr told both the police and the Associated Press that he's responsible for the child's death in Boulder, Colo., 10 years ago, but members of his family have their doubts. His ex-wife says he was with her in Alabama at the time, and Karr's brother says he never spent any time in Boulder. If he turns out to be innocent, why might he have confessed?
For notoriety, or because he'd become obsessed with the case. Psychologists who study false confessions divide them into "voluntary" and "coerced" admissions of guilt. Someone might make a voluntary false confession if he wanted to be famous. Several hundred people claimed to have abducted the Lindbergh baby, for example, and more than 30 confessed to the Hollywood "Black Dahlia" murder in the 1940s. Just a few weeks ago, a prison inmate named Robert Charles Browne confessed to murdering 48 people. Police were instantly suspicious, as this number just happens to put him in the company of the notorious Green River Killer.
If Karr did lie to the police, it may be because he became so immersed in the high-profile case that he started to think he'd committed the crime. Reports say Karr had been working for several years on a book about JonBenet's murder, and child murders in general. A similar obsession seems to have led crime-novel buff Laverne Pavlinac to implicate herself and her boyfriend in an Oregon murder in 1990. Both were convicted of the crime but were released five years later when the so-called Happy Face Killer admitted to being the true culprit. Pavlinac later said she'd made the confession to escape an abusive relationship. Her boyfriend said he'd confessed to avoid getting the death penalty.
Experts say that false confessions are much more often coerced than voluntary. Police interrogations can lead innocent people—like Pavlinac's boyfriend—to admit guilt so as to avoid harsher punishment. They can also push a suspect to question his own recollection of events or to create false memories. In general, young people with low IQs are considered the most vulnerable to this kind of false confession. (In scientific terms, they score the highest on the Gudjonsson Suggestibility Scale.) A classic example is the Central Park jogger case, in which five boys with low IQs confessed to rape but later turned out to be innocent. (The actual rapist stepped forward 13 years later.)
Bonus Explainer: How do police know when a confession is real? They try to connect it with physical evidence. When the Happy Face Killer confessed in 1995, he revealed the location of his victim's purse and ID card. (Pavlinac hadn't been able to provide those details when she confessed five years earlier.) In the Central Park jogger case, cops were able to match a DNA sample to the man who eventually confessed.
Bonus Bonus Explainer: Is it illegal to make a false confession? Technically, yes. In many jurisdictions, you're committing a crime when you make false statements to the police. You're more likely to get charged with that offense, though, if you're a third party who gives the cops a false tip.
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Explainer thanks Eric Ferrero of the Innocence Project.