DNA clue in Derek Percy child murders HE'S long been suspected in a number of cold cases but child killer Derek Percy took his secrets to the grave yesterday. Police now hope DNA will answer the questions Percy refused to answer. Even as he lay dying, police questioned him about his involvement in up to six murders - including some of the most high-profile outstanding cases in Australia. Percy - held on insanity grounds after he abducted and murdered 12-year-old Yvonne Tuohy in 1969 - has been linked to the disappearance of the three Beaumont children in 1966 and the Wanda beach murders in Sydney in 1968.DNA was taken from the 64-year-old Percy in the months before his death and has been offered to cold case squads around Australia. "That DNA was made available to us to use in the ongoing Wanda beach case," NSW unsolved homicide unit head Detective Chief Superintendent John Lehman said. It was revealed last year that a DNA sample was taken from a blood smear found at the scene from the murders, 47 years ago, of 15-year-olds Marianne Schmidt and Christine Sharrock. "The sample is very old and degraded and a lot of work needs to be done by the lab," Supt Lehman said. Percy was also a suspect in the 1968 murder of three-year-old Simon Brook in Glebe. Victorian police pushed Percy to confess to the Brook murder and others while he was suffering from cancer before he died in Melbourne Hospital at 2am yesterday. Percy was questioned by the coroner as a suspect in 2005 but refused to answer. He also was linked to the disappearance of the Beaumont children in Adelaide.