The world’s most prolific killer, Shipman is estimated to have killed 275 people, but the actual figure will never be known. The 57-year-old GP was given 15 life sentences to run concurrently for the murders, and four years for forging a will, but hung himself in his cell after he was sentenced. He always denied his crimes. When the police began investigating Dr Harold Shipman in September 1998 they struggled to understand him. How could a GP who was trusted and respected by more than 3,000 patients also be a killer who struck time after time with no obvious motive? The coroner speculated that ‘the only valid possible explanation for it is that he simply enjoyed viewing the process of dying and enjoyed the feeling of control over life and death, literally over life and death …’

Jeffrey Dahmer was a homosexual sexual deviant who raped, murdered and ate parts of 17 victims. Like other killers such as John Wayne Gacy, he managed to elude capture while continuing to carry out his crimes. Like every other sociopath serial killer in history he believed himself to be completely justified in his actions. Why does a Jeffrey Dahmer happen? How does a man become a serial killer, necrophiliac, cannibal and psychopath? Many of the theories would have you believe that the answers can always be found in childhood abuse, bad parenting, head trauma, foetal alcoholism and drug addiction. Perhaps in some cases these are contributing factors, but not for Jeffrey Dahmer…

For many years, Myra Hindley was depicted by the tabloid press as "the most hated woman in Britain". The crimes committed by Hindley and her lover, Ian Brady, shocked the nation and became the benchmark by which other acts of evil came to be measured. Until she met Brady, Hindley had been, by all accounts, a perfectly normal girl, with strong religious feelings. She loved children and animals, and was much in demand as a babysitter. When they became lovers, Hindley was prepared to do anything Brady asked… Can people be persuaded to kill for love? Were they crimes of passion? Brady claimed that Hindley was a manipulative liar who was as committed to murder as he had been…

Two black Americans, John Allen Muhammad, 42, a veteran of the Gulf War in 1991, and his stepson John Lee Malvo, 17, were convicted in 2004 of being the ‘Washington sniper’, who had been terrorizing America over a period of three weeks. Police found a gun in the suspects car - the criminals had supposedly shot it 13 times. Ten innocent people were killed, and three were wounded. Police also found a scope and a tripod. The criminals probably shot the victims without even leaving the car, as it has an opening in the trunk that allows people to lie hidden and shoot the victims. Experts unanimously agreed that it was John Allen Muhammad who was the force of the criminal tandem. What were the motives of these men, and was one ‘guiltier’ than the other? Psychologists suppose that John Allen Muhammad is non compos mentis, but find it difficult to explain why the stepson acted in the same way…

The Back Pack Killer. Australia's worst solo serial killer, Ivan Milat, is now serving life for the murders of seven hitchhiking backpackers between 1989 and 1992. Many questions remain unanswered and there is uncertainty about the full extent of Ivan Milat’s crimes. Did he murder for entertainment? Some say his motivation lay in his family background and upbringing. Ivan Milat grew up as one of 14 siblings, a close-knit family who didn’t mix with others. They were surrounded by guns amidst an ethos of lawlessness and unbreakable family loyalty. Did he kill alone? One of his siblings, Boris, broke the bonds of rigid family loyalty to speak out against the convicted killer. He said it was likely there were more of his victims that haven’t yet been found…