Derek Percy

Percy died from lung cancer in St Vincents Hospital, Melbourne on 23 July 2013, aged 64, without admitting to any further crimes. At the time, he was the longest serving prison inmate in Australia, some 44 years.

Percy repeatedly stated, however, that he could not remember whether or not he had committed any further crimes. Detectives then started trying to piece together his movements around Australia at the time of the murders. They were aware the Percy family often took caravan holidays during yachting regattas near beaches (where most of the crimes took place), that his transfers within the navy brought him close to many of the crime scenes, and knew that he was harbouring paedophilic and psychopathic fantasies towards children. In 2007, a cache of 35 boxes of Percy's diaries, drawings, maps, and newspaper clippings was found in a storage unit in South Melbourne, casting further suspicion on him.

Percy was arrested at Cerberus, adjacent to Crib Point on the Mornington Peninsula south of Melbourne, for the murder of 12 year-old Yvonne Tuohy at Ski Beach, near Warneet on Westernport Bay, on 27 July 1969. At the time he abducted Tuohy at knife-point, he also tried to abduct her friend, Shane Spiller, age 11, who only escaped by threatening Percy with his tomahawk. Spiller, however, was able to describe to police the abductor and his vehicle, an orange Datsun station wagon with a navy sticker on the back window. Police, accompanied by Spiller, then went to Cerberus and discovered Percy machine-washing blood off his clothes. When questioned, Percy denied involvement, but eventually led police to Tuohy's mutilated body in a paddock on Fisheries Road at Devon Meadows, some 8 kilometres (5 mi) from the abduction scene. Police also found Percy's journals describing and illustrating his bizarre sexual fetishes (including coprophilia, urophilia, and cannibalism). In 1970, he was found not guilty, by reason of insanity, of the murder and remanded indefinitely.

Percy began to attract the attention of authorities in late 1964, when he started stealing and wearing female underwear and dresses and mutilating dolls with knives and razor blades. In 1965, the family relocated to Khancoban in New South Wales (their sixth move in twelve years) where Percy began writing down bizarre and violent sexual fantasies. In 1966, he repeated year 11, then tried year 12 in school, but dropped out and joined the Australian Navy as a naval rating in electrical mechanics in November 1967. He was posted to the aircraft carrier HMAS Melbourne in March 1968, the troop ship HMAS Sydney on 1 July 1968, and HMAS Cerberus naval base in April 1969.

Derek Ernest Percy (15 September 1948 – 23 July 2013) was an Australian suspected serial killer and convicted child killer who was also a person of interest linked to the mysterious deaths and disappearances of multiple children in the 1960s, including the Beaumont disappearances and the Wanda Beach murders.

Derek Percy was born on 15 September 1948 in Strathfield, New South Wales, the eldest of three sons of parents Ernest and Elaine Percy. Percy's father, a sailing enthusiast, had been a New South Wales railway electrician before deciding to take a job with the State Electricity Commission in Victoria, and moving to Chelsea in 1954, then to Warrnambool in 1957, and to Mount Beauty, near Bright, in 1961.