Firstly, let's be very clear - false confessions are far more common than most people think. In a disturbing number of cases in which DNA evidence later proved the person to be innocent, around 25 %, they had in fact confessed to committing the crime.
According to some reports, some 80 % of crimes are eventually solved by a confession - so it is essential, though actually uncommon, for detectives to be properly trained to obtain accurate, uncoerced, and uncontaminated statements from people being questioned. And such sessions should be videotaped, or at least audiotaped, for later review.
And judges and juries tend to trust confessions rather too readily. And the commonest single cause of a miscarriage of justice and the conviction of an innocent suspect, is the coerced confession.
Psychoanalysts have suggested that some people have a neurotic urge to confess and to seek punishment.
Overcome by guilt
Sometimes, people offer confessions without prompting because they're overcome by guilt over a crime; often, a religious conversion can motivate someone to admit culpability he or she had previously concealed. And sometimes, the prospect that someone else has been wrongly convicted serves as an incentive.
The lure of attention or publicity associated with infamous cases also has inspired people to confess to crimes they never committed, among them the 1930s Lindbergh kidnapping. The risks of a false confession NOT coerced by the detectives, but by social and media pressures, seems much greater in heavily publicised cases.
Early in the last century, after the kidnapping of the baby of the flying hero Charles Lindbergh, over 200 people confessed to having committed the crime.
In the 1940's after the sensationalised mutilation murder of Elizabeth Short in Los Angeles (the so-called Black Dahlia case) over 30 people confessed to having killed her, yet the crime has never been solved. There's a story that the appalling Nazi SS leader, Heinrich Himmler lost his pipe during a visit to a concentration camp. When he returned to his car, he found it on his seat - but by then, six prisoners had already confessed to having stolen it.
There are at least three distinct types of false confession. A Voluntary False Confession is when a person falsely incriminates themselves without pressure from the police, even though they know the likely consequences of doing so.
These may arise from a morbid wish to be notorious, to be a celebrity at any cost. Or to impress others. Gudjonsson studied the case of Henry Lee Lucas who confessed to over 600 murders and is generally recorded as a major serial killer, and emphasised how eager Lucas was to please and impress his audience.
Or this may be done to protect someone else, or out of a desire for self-punishment stemming from severe guilt aroused by other things they may have done, even if not criminal.
Then there are Coerced-Compliant False Confessions, when someone who knows they are not guilty confesses due to the method of interrogation used. Examples of this go back at least to the notorious Salem Witch trials in the 17th century.
More recent are the techniques that came to be known as "brainwashing", first publicised during the Korean War, when American captives were induced to confess to acts the West knew had not occurred. Something similar was seen in the Vietnam War, and even in the 1991 Gulf War where some captured American airmen were persuaded to condemn their own government's actions.
In South Africa, during the Apartheid era, similar methods were used by police interrogators of suspected ANC operatives, along with frank torture, in some cases producing the desired confessions or statements, even if these might be highly inaccurate.
And then there are Coerced-Internalised False Confessions. In these, a vulnerable but innocent suspect who is anxious, exhausted, and placed under highly suggestive interrogation, actually becomes convinced that they really did commit the crimes of which they are suspected. Their own actual memory of events may be shifted in line with the beliefs of their interrogator, and become hard to recover. The most vulnerable for this are young, naive, trusting, suggestible, unintelligent or unsophisticated, stressed, and drunk or drugged people.
Recent research by colleagues of mine in North America, such as the remarkable Elizabeth Loftus, has shown how surprisingly easy it is to plant false memories of specific childhood experiences which actually never occurred. It is much easier than most people think, to induce, deliberately or even accidentally, trance-like states of high suggestibility.
Psychoanalysts have suggested that some false confessions can be motivated by a subconscious psychological need to be punished for something a person wants to do but has not. Karr has been convicted on child pornography charges and has expressed fascination with young girls in general and the murders of both JonBenet Ramsey and Polly Klaas in particular.
Experts are also curious about Karr's insistence that the killing was an accident. The assertion may be an attempt to avoid charges of first-degree murder, said Sharon L. Davies, a professor at Ohio State University law school. But it could also reveal a discrepancy between the forensic evidence, which indicates a brutal attack, and Karr's fantasy of the crime he thinks he committed. – Prof M.A. Simpson, CyberShrink
Karr: The suspicious suspect
What can we make of Karr's confession?