When Charles A. Lindbergh's infant son was kidnapped and murdered in 1932, more than 200 people confessed to the crime. But not the man who was convicted.
In 1947, scores stepped forward to claim responsibility for the grisly Hollywood "Black Dahlia" murder of aspiring actress Elizabeth Short. Her killer was never found.
Now that Colorado prosecutors have dropped charges in the 10-year-old murder case of child beauty queen JonBenet Ramsey, the 41-year-old itinerant teacher they arrested, John Mark Karr, joins the long line of people who confess to notorious crimes they didn't commit.
Which leaves the question: Why confess to something you didn't do?
"There are a number of ways it can happen," said Arnett Gaston, a clinical psychologist and criminologist at the University of Maryland, College Park.
Gaston and other mental health experts said voluntary false confessions often arise from a toxic psychological brew of obsession, delusion, guilt and self-loathing.
The best explanation for behavior like Karr's, Gaston said, might be an out-of-control fantasy life driven by an obsessive-compulsive personality.
Karr, who is obsessed with the killing of JonBenet, was arrested Aug. 16 in Thailand after he sent hundreds of detailed e-mails about the case to a University of Colorado journalism professor.
Officials said Karr's messages displayed an intense infatuation with the girl and included graphic descriptions of alleged sexual acts with the victim.
In addition to the Ramsey case, Karr was reportedly obsessed with the 1993 killing of 12-year-old Polly Klaas, who was killed after she was abducted at knifepoint from her home in Petaluma, Calif.
"Some people get so into a fantasy it begins to take over their lives," Gaston said. "He had fantasies about this girl and what he would like to do with her. He may have started living his fantasy."
Another reason fabricators concoct these tales, experts said, is to fulfill a desire for fame -- by confessing to high-profile crimes, they thrust themselves into the public spotlight.
Dr. Robert T.M. Phillips, a forensic psychiatrist in Annapolis, said many false confessors are characterized by this desperate need for attention -- even if it means their identification with a heinous crime, such as murder, rape or child molestation.
"In some individuals, the negative attention is far more intoxicating and far more pleasing, because that's the kind of attention that generates media frenzy," said Phillips, an adjunct professor with the University of Maryland's law and medical schools.
"The common thread psychologically is that there is a clear void inside," Phillips said. "There is really a need for them to somehow establish and improve upon their own self-worth by being linked to the famous and the infamous."
That desire for fame might explain past cases of people confessing to high-profile crimes.
The kidnapping and murder of Lindbergh's son, Charles Jr., was probably the most famous case of this sort. The 20-month-old boy disappeared from the second-story nursery of the family's New Jersey home in 1932. The boy's badly decomposed body was found more than a month later a few miles from the house.
Nearly 200 people stepped forward to confess to the crime, but none of them turned out to be the culprit. A carpenter named Bruno Richard Hauptmann was convicted of the murder and executed in 1936 -- although there are still devotees of the case who doubt his guilt.
The "Black Dahlia" murder, as the killing of Elizabeth Short is best known, occurred 15 years later and drew its share of false confessions. Friends gave the would-be actress that nickname because of her dark hair and the popularity of a movie of the same period titled The Blue Dahlia.
When Short's body was found, naked and cut in half in a vacant lot in Los Angeles, the story generated extensive media coverage and national headlines. Police heard scores of confessions but none panned out, and the killer was never identified.
Almost 60 years later, that case still mystifies and intrigues the public. Universal Pictures will release its fictional version of the Black Dahlia killing, starring Scarlett Johansson, on Sept. 15.
Dr. Jack Vaeth, a psychiatrist with the Sheppard Pratt Health System, said another common reason people own up to crimes they didn't commit is a sense of guilt about something they did do.
"They feel a compulsive guilt to confess to something," he said.
Although DNA evidence failed to link Karr to the Ramsey case, leading prosecutors to drop charges Monday, he is charged with five unrelated misdemeanor counts of possessing child pornography in a California case from 2001.
"An individual who gets caught possessing child pornography may decide to go ahead and punish himself by confessing to a greater crime," Vaeth said.
Vaeth also warned that it is hard to predict the behavior of those caught up in obsessions with young girls and murder.
"Some sex crimes escalate, and some do not," he said. "You have to be concerned with what the root of the problem is, and if it is going to get worse."
Sun reporter Jonathan Bor contributed to this article.