Samenow, who has interviewed multiple serial killers, said the Ted Bundy-style stereotype of a personable - even charismatic - serial killer is often true. 'It's probably not surprising that serial killers would lie,' Aamodt said. While convicted serial killers often report childhood abuse, Aamodt said, he warned that the refusal to take responsibility for their actions means that serial killers' childhood reminiscences should be taken with a grain of salt. They often show early personality traits such as a need to be in control and the refusal to take responsibility for wrongdoing, but the factors that create these traits aren't known.

His take, he said, is that serial killers come from all walks of life. 'You can ask eight experts and get 10 opinions on that,' he said. The development of a serial killer is not well-understood, Samenow said, including the role of childhood abuse. 'They have a view of themselves as being the hub of the wheel around which everything else should revolve.' 'These are people for whom life is not acceptable unless they have the upper hand,' he said. In many ways, serial killers are similar to other chronic criminals, Samenow said. Some kill for money, others for revenge and still others for the thrill of it. Serial killers - the term that generally refers to someone who kills three or more people with a 'cooling off' period in between murders, though some experts argue that the definition should include killers with two victims - have many motivations, Samenow told LiveScience. The problem with profiling the average serial killer is that there is no such thing, said Stanton Samenow, a criminal psychologist and author of the book 'Inside the Criminal Mind' (Crown, 1984).

What makes a serial killer