The case of the Beaumont children has horrified Australians since Jane, nine, Arnna, seven, and Grant, four, vanished on a summer day in 1966. Their bodies were never found.
Derek Percy was jailed indefinitely in 1969 for murdering Yvonne Tuohy, 12, whom he abducted from a beach in Victoria and sadistically mutilated. On Wednesday, detectives acting on a new lead escorted him to a Melbourne police station where they quizzed him for nine hours about the Beaumont children and other unsolved cases.
A police source told The Melbourne Age newspaper that Percy, 55, was "intelligent, cunning and pure evil". One prison officer said: "He's highly intelligent, but you could never get a handle on his real feelings." Referring to the character in Silence of the Lambs, he added: "He's our Hannibal Lecter."
Detectives from three forces questioned Percy, a former naval rating, about the murder of five other children, aged between six and 15, in Sydney, Canberra and Melbourne in the 1960s. According to The Age, police have established that, in each case, he was near the scene, either on holiday or stationed at a military base.
In the Tuohy case, he was found unfit to plead on grounds of insanity, and is now Victoria's longest serving prisoner. In 1998 a judge rejected his application for a fixed-term sentence, saying he had "demonstrated no significant remorse or anxiety" and had not received treatment for a condition described as sadistic paedophilia.
New information leading police to Percy was uncovered during an inquiry into historic unsolved child murders. It is believed that some DNA evidence was recovered from crime scenes, although a sample was never taken from Percy because he was not convicted.