Derek Ernest Percy was a young sailor in the Royal Australian Navy when, in 1969, 12-year-old Yvonne Tuohy died at Warneet, on Western Port, southeast of Melbourne. Percy admitted the killing. A Victorian court found him not guilty on the grounds of insanity in 1970, and he was detained at the Governor's pleasure. That verdict is not a conviction, and he was never convicted of any offense. He remained in detention for the rest of his life and died in a Melbourne hospital on July 24, 2013, at the age of 64.
His name stayed in the news because of what police suspected rather than what a court had decided. For more than four decades detectives in four states asked whether he had a part in the deaths of other children in the 1960s. In October 2014, after his death, a Victorian Deputy State Coroner found that he had caused the death of seven-year-old Linda Stilwell in 1968. That is a coronial finding made after an inquest, not a verdict in a criminal trial. In the other cases he was a suspect in the eyes of police and some retired officers, and he was never charged.
Percy's childhood, his family, and his date and place of birth are not on record. The record starts with his naval service. The Dandenong Star Journal reported in 2008 that he trained in electrical work at HMAS Cerberus and that between 1967 and 1969 he went to sea as an ordinary seaman. A former shipmate told the paper he shared a dormitory with Percy for eleven weeks. He described a quiet, intelligent young man who kept to himself and read a great deal, and he said senior officers had been considering whether Percy might be made an officer.
The navy posted its sailors to many places, and that later mattered to detectives. Cold-case inquiries placed him in Sydney in 1968, when he was stationed there with the navy, and said he later acknowledged to police that he had been in Adelaide in 1966. In a 1969 police interview about the Beaumont children, SBS News reported in 2013, he said: "I could have killed them, I don't remember a thing." The statement is an answer in an interview. It was not a confession, and South Australia Police told reporters in 2013 that they had never treated him as a significant person of interest in that case.
Yvonne Tuohy was 12. She died at Warneet, on Western Port.
Reports differ on the timing. ABC News described the case as one that began in July 1969. The Dandenong Star Journal gave the date of Percy's arrest as June 20, 1969. The two accounts cannot both be right about the sequence. What every report agrees on is the year, the place, Yvonne's age, and that Percy was a serving sailor when he was arrested.
ABC News reported in 2013 that Percy was charged with the murder of Yvonne Tuohy, with other charges. SBS News reported in 2014 that he admitted killing her and that she was the only death he ever admitted. When the Stilwell inquest ended in 2014, the coroner described his condition as rare and dangerous, ABC News reported.
The exact wording of the verdict matters, because the press has not always used it. A law journal article by Julie Debeljak, published in the UNSW Law Journal in 2015, states that in 1970 Percy was found not guilty of murdering a 12-year-old girl on the grounds of insanity and was detained at the Governor's pleasure. SBS News used the same phrase, "not guilty on the grounds of insanity", in its reports of 2013 and 2014. ABC News reported the outcome in different words on different occasions: "found criminally insane and jailed indefinitely" in April 2013, "not guilty of the Tuohy murder on grounds of insanity" in July 2013, and, in a 2009 report, that a court had ruled he was "unfit to plea on the grounds of insanity". The phrase "unfit to plead" describes a different legal finding from an insanity acquittal, and the 2009 wording stands alone against the others.
An insanity acquittal is not a conviction. Under the law then in force in Victoria, a person found not guilty on the ground of insanity was held in strict custody until the Governor's pleasure was known, as the Victorian Law Reform Commission describes the old system. The Governor decided when, if ever, the person could be released, and there was no fixed term. Some press reports called Percy a convicted killer or said he was "jailed", and they misdescribe the outcome.
The date of the hearing, the judge, the lawyers and the name of the court beyond its being a Victorian court are not on record.
Percy spent about 43 years in custody, which made him Victoria's longest-serving prisoner, a description used in ABC and SBS reports from 2005 to 2014. He was held at the Governor's pleasure until 1998. According to Debeljak, that arrangement ended when the Crimes (Mental Impairment and Unfitness to be Tried) Act 1997 took full effect, and from then on he was deemed to be subject to a custodial supervision order. The Victorian Law Reform Commission records that the Act began full operation on April 18, 1998.
He was held in prison throughout, not in a secure hospital. Debeljak writes that he was the only person in Victoria found not guilty by reason of insanity who was kept in a prison. He was transferred to a regional prison so that he could take part in a treatment program, and Debeljak notes that Percy supported the transfer "if it [was] permanent". In August 2009 ABC News reported that he had applied to the Supreme Court to be moved out of jail to another facility for treatment, and that his custody was under review. Debeljak also discusses an undated statutory review of his custody order: Justice Coghlan confirmed the order and declined to change where he was held. The judge was not satisfied that a secure mental health hospital would be less restrictive than prison. Debeljak argues that the judgment gave too little attention to the state's human rights charter.
Percy's name was linked to other cases through police work in several states, and the way each link is described differs from case to case. The record separates into a coroner's finding in one case and suspicion in the rest.
In February 2005 ABC News reported that detectives from a joint cold case taskforce of Victoria, New South Wales and the Australian Capital Territory had obtained a Melbourne magistrate's permission to question him about unsolved child deaths of the 1960s. In August 2007 a magistrate again authorized an interview. Police at that time named him as a suspect in the Wanda Beach case in Sydney and linked him to the Beaumont children in Adelaide. Whatever he said in those interviews, no charge followed.
Simon Brook. Simon Brook was three when he died in Sydney in 1968. Percy was a sailor stationed in Sydney then. In December 2005 ABC News reported that a New South Wales detective sergeant, Adam Barwick, believed Percy was responsible, and that he could find no police record ruling Percy out. A 2005 coronial inquest recommended that Percy be referred to the Director of Public Prosecutions. ABC News reported in 2013 that the Director at the time, Nicholas Cowdery, decided there was not enough evidence to proceed. Percy was not charged.
Wanda Beach. Christine Sharrock and Marianne Schmidt, both 15, died at Wanda Beach in Sydney on January 11, 1965. No one has been charged. SBS News reported in 2013 that Percy was believed to have been holidaying near Wanda at the time, and ABC News reported that police questioned him about the case in 2007. In January 2025 ABC News quoted a former detective inspector, Ian Waterson, who named Percy as another person of interest. No police statement about Percy accompanied the report, and the case remains open with a reward on offer.
The Beaumont children. Jane, Arnna and Grant Beaumont were 9, 7 and 4 years old in January 1966, when their case began in Adelaide. ABC News reported in 2013 that Percy was linked to the case in the press and that South Australia Police said they had never treated him as a significant person of interest.
Alan Redston. Reports in 2013 listed a six-year-old boy in Canberra, in 1966, among the cases in which Percy was suspected. ABC News reported that the Australian Federal Police named a different man as a suspect in 2003 and could not establish a link to Percy. The boy's name is spelled "Allen" in one ABC report and "Alan" in another.
A tally of nine children appears in some coverage. ABC News traced it to a crime writer, Debi Marshall, who said that during the Tuohy investigation Percy's name was linked to eight other child killings and that police had reason to suspect him in each. SBS News repeated the count, describing him as a suspect in the deaths of nine children in four states. The number is a statement of suspicion, and no court has made a finding on any of them beyond the Stilwell inquest.
Linda Stilwell was seven years old when she died in August 1968 in the St Kilda area of Melbourne, a few days before her eighth birthday, according to ABC News. Her death was the subject of a coronial inquest that began in 2009 and ended with findings in 2014. Her mother and her brother, who was nine at the time, pressed the case for years.
A detective senior sergeant, Wayne Newman, took up the cold case in 2004, SBS News reported. Newman told reporters in 2014 that police began by trying to rule Percy out and "were unable to do so", and said he was "absolutely" certain Percy was responsible. In 2009, ABC News reported, the coroner ruled that Percy did not have to give evidence. Linda's mother challenged the ruling. The matter went to the Supreme Court and then to the Court of Appeal, which ruled in her favor in December 2012, SBS News reported, and ABC News said the Court of Appeal's ruling meant the inquest should be reopened and Percy should be offered immunity from prosecution. The coroner remained doubtful about the reliability of any evidence he might give, ABC News reported in April 2013.
In July 2013 Percy was dying of cancer in a secure hospital ward. Linda's family asked for an urgent hearing, and a Deputy State Coroner held it at his bedside on a Saturday night in July 2013, according to the ABC report of his death. He denied any involvement and said he had been in Newcastle at the time, ABC News reported in 2014. Chief Commissioner Ken Lay of Victoria Police said the force was very disappointed and that Percy "either couldn't or wouldn't share information".
Deputy State Coroner Iain West delivered his findings on October 30, 2014. ABC News reported that he found Percy "caused the death" of Linda Stilwell. SBS News reported the formal finding as that Linda was killed by Derek Ernest Percy. West described the evidence against Percy as circumstantial. He said it was more probable that Percy was responsible than that another person in the area was, SBS News reported. A non-publication order dating from 2009 limited what the ABC could report from the ruling.
The finding was a coroner's finding of fact about a death. It did not create a conviction, and Percy, who had died, could not be tried.
Percy died at St Vincent's Hospital in Melbourne at about 1:30 a.m. on Wednesday, July 24, 2013, aged 64, ABC News reported. He had lung cancer. The reports said he died after about 43 years in detention, and that police had questioned him in hospital about more than half a dozen unsolved cases without result. Chief Commissioner Lay said Percy was "a very frail man" in his last days. Linda Stilwell's mother said she believed he knew what had happened but would not say.
Four points separate what is established from what is claimed.
First, he is sometimes called a convicted killer. He was not convicted. The one court verdict in his case was an acquittal on the grounds of insanity, and the one finding that he caused a death came from a coroner, not a jury.
Second, the Stilwell finding rests on circumstantial evidence, as the coroner said. It rests on his presence in the area and the absence of any more likely candidate. It was made after Percy could no longer answer.
Third, in the Wanda Beach, Beaumont, Brook and Canberra cases there is no finding and no charge. In the Brook case an inquest recommended a referral to the Director of Public Prosecutions, and the Director decided the evidence was not enough. In the Beaumont case the investigating police force has said Percy was never a significant person of interest. The tally of nine children is a reporter's and a crime writer's count of suspicions.
Fourth, the reports differ on the date of the Tuohy case (June or July 1969).
Percy's detention is discussed in legal writing on how Victoria holds people found not guilty by reason of insanity. He was held at the Governor's pleasure until the 1997 Act took effect, and then under a supervision order. The judge's refusal to move him from prison to a hospital is analyzed by Debeljak in a study of prisoners' rights under the Victorian charter of human rights.
For the families the aftermath was the inquest. Linda Stilwell's mother and brother spent years in the courts to have the coroner hear from Percy. In December 2012 the Court of Appeal ruled in her mother's favor. Chief Commissioner Lay said police were disappointed that Percy shed no light on the case before he died. The Wanda Beach case remains open, with a reward on offer as of January 2025.
1965, January 11: Christine Sharrock and Marianne Schmidt, both 15, die at Wanda Beach, Sydney; Percy is later named as a suspect and person of interest; no one has been charged.
1966, January: the Beaumont case begins in Adelaide; Percy is later linked to the case in the press; South Australia Police say he was never a significant person of interest.
1967 to 1969: Percy goes to sea as an ordinary seaman in the navy.
1968: Simon Brook, 3, dies in Sydney; Linda Stilwell, 7, dies in St Kilda, Melbourne, in August.
1969: Yvonne Tuohy, 12, dies at Warneet; Percy is arrested (June 20, according to the Dandenong Star Journal) and charged.
1970: Percy is found not guilty on the grounds of insanity and detained at the Governor's pleasure.
1998: the 1997 Act takes full effect (April 18); Percy is deemed subject to a custodial supervision order.
2004: Detective Wayne Newman takes up the Stilwell cold case.
2005: Percy is questioned by a joint cold case taskforce; a coronial inquest into the death of Simon Brook recommends a referral to the Director of Public Prosecutions, who finds the evidence insufficient.
2007: Percy is questioned again.
2009: the coroner rules Percy need not give evidence in the Stilwell inquest; Percy applies to the Supreme Court to be moved to another facility for treatment; the Stilwell inquest begins in December.
2012: the Court of Appeal rules for Linda Stilwell's mother in December.
2013, July: a Deputy State Coroner hears Percy at his hospital bedside and he denies involvement. July 24: he dies, aged 64.
2014, October 30: Deputy State Coroner Iain West finds that Percy caused the death of Linda Stilwell.
2025, January: Wanda Beach murders remain unsolved, with a reward on offer.