Offender Record · OFF-2026-197
Derek Percy (photo from the Radford University biography)
Derek Ernest Percy
Sex
Male
Race
White
Born
1948
Custody
Deceased
States
AU, CA
This record documents arrests, charges and convictions reported by courts, law enforcement agencies and news organizations. Every statement is tied to a cited source with an archived copy. A charge is an accusation, not proof of guilt; a person charged is presumed innocent unless convicted. Where a record says named by police, no charge was ever filed: the record rests on a law enforcement agency's public identification of the deceased person, cited below. Not guilty by reason of insanity means the court found the act proven but the person not criminally responsible. Solve the Case does not allege that this person committed any offense beyond what the cited records state, and this record is not a suggestion that the person is connected to any unsolved case. How records are built, corrected and removed.
Summary of the record
Derek Ernest Percy was found not guilty by reason of insanity in April 1970 for the abduction, torture and murder of 12-year-old Yvonne Elizabeth Tuohy at Warneet, Victoria, on 20 July 1969. Percy was arrested on 21 July 1969 at the HMAS Cerberus naval base. He was detained indefinitely at the Governor's pleasure and died in custody from lung cancer on 23 July 2013, having served approximately 44 years in detention.
Documented Arrests, Charges and Convictions
Dispositions are shown exactly as the cited records report them. Pending charges are updated when a court acts; a record with no remaining conviction or pending charge is removed from the site.
Offense date Jul 20, 1969, Warneet, Victoria
Murder
Victoria Police · Supreme Court of Victoria · Section 3, Victoria's Crimes Act 1958 · Arrested Jul 21, 1969 · Not guilty by reason of insanity Not guilty by reason of insanity · Sentence: Indefinite detention at Governor's pleasure
12-year-old Yvonne Elizabeth Tuohy was abducted at knifepoint from Ski Beach near Warneet on 20 July 1969 while walking with 11-year-old friend Shane Spiller. Witness Shane Spiller escaped by threatening Percy with a tomahawk and reported the vehicle description and naval insignia. Percy's body was found 8km away at Fisheries Road, Devon Meadows, with wrists bound behind back, mouth gagged with cloth, throat cut, and evidence of strangulation and mutilation. Percy initially confessed to police but later claimed memory loss. Found not guilty by reason of insanity on 10 April 1970 and remanded indefinitely to Governor's pleasure.
SourcesDerek Percy; Child killer Derek Percy dies in hospital; Derek Percy; In the matter of a Major Review of Derek Ernest Percy 2010 VSC 179; Radford University serial killer biography: Percy, Derek
Pattern and Background
Victim counts and the pattern of the offenses as stated by courts, agencies and the cited reporting. Suspected counts are what officials have said publicly, not a finding of this site.
0
Victims convicted
1
Victims confessed
9
Victims suspected
Active years
1965–1969
Victim profile
Children
Stated motive
Sexual, Thrill
Range from home
regional
Education
some high school
Marital history
Never married
Children
0
Died
2013-07-23 · natural
Agencies
Law enforcement, prosecutors and corrections agencies the records show dealing with this person. An investigator working a case with a possible connection can start here.
Department of Human Services (Victoria) · VI
Administered Aradale Mental Hospital where Percy was initially committed in April 1970
Supreme Court of Victoria · VI
Trial held 2-10 April 1970 before Justice A.F. Starke; jury found Percy not guilty by reason of insanity; sentenced to indefinite detention at Governor's pleasure
Victoria Police · VI
Agency case Yvonne Tuohy murder investigation
Arrested Derek Percy on 21 July 1969 at HMAS Cerberus after witness Shane Spiller identified vehicle; discovered Tuohy's swimsuit and notebooks with graphic descriptions in his vehicle
Royal Australian Navy · VI
Percy's service record shows postings to HMAS Melbourne (March 1968-July 1968), HMAS Sydney (July 1968-April 1969), and HMAS Cerberus (April 1969-July 1969); Naval police would have assisted in initial investigation
Director of Public Prosecutions Victoria · VI
Prosecuted the case against Derek Percy in Supreme Court of Victoria; Crown Prosecutor G.L. Kneale led prosecution presenting forensic and circumstantial evidence
Corrections Victoria · VI
Managed Percy's custody across multiple facilities from 1970 to death in 2013; last facility Port Phillip Prison before transfer to hospital
Places Lived, Worked and Frequented
Each place and date range comes from a cited record. Dates marked approximate are as reported. Know a place that is missing? Use Edit record under the photo; a moderator reviews it before it appears.
AU
Strathfield, New South Wales, Australia
1948 – 1956 · Birthplace; lived with parents Ernest and Elaine Percy
Chelsea, Victoria, Australia
1956 – 1959 · Family moved from NSW
Warrnambool, Victoria, Australia
1959 – 1961 · On Victoria's south-east coast
Mount Beauty, Victoria, Australia
1961 – 1965 · Family moved; attended school; Prefect in 1964; worked part-time in tobacco fields
Wallsend, New South Wales, Australia
1966 – Nov 1967 · Family moved from Victoria after Percy's school problems
Sydney, New South Wales, Australia
Nov 1967 – Mar 1968 · Accepted into Royal Australian Navy with service number R66951; trained as Electrical Mechanic; nicknamed 'The Ghost' · navy
Sydney, New South Wales, Australia
Mar 1968 – Jul 01, 1968 · Stationed on aircraft carrier HMAS Melbourne; docked at Cockatoo Dry Dock for year-long refit; lived at Garden Island naval base · navy
Melbourne, Victoria, Australia
Jul 01, 1968 – Apr 1969 · Transferred to troop ship HMAS Sydney based in Melbourne; took 18-day leave from 5 August 1968 · navy
Crib Point, Victoria, Australia
Apr 1969 – Jul 21, 1969 · Stationed at HMAS Cerberus naval base on Mornington Peninsula, Westernport Bay, 90km southeast of Melbourne; attempted abduction of 12-year-old girl on bicycle near base on 1 April 1969; arrested here on 21 July 1969 · navy
Ararat, Victoria, Australia
Apr 1970 – Aug 1986 · Aradale Mental Hospital (formerly Ararat Mental Hospital); committed under Governor's pleasure; prison search September 1971 found pornographic writings and abduction blueprints; worked in printing industry for 11 years
Beechworth, Victoria, Australia
Aug 01, 1986 – Sep 09, 1987 · Transferred to medium-security facility
Castlemaine, Victoria, Australia
Sep 09, 1987 – Jun 1993 · Prison facility
Ararat, Victoria, Australia
Jun 1993 – Nov 24, 2003 · Hopkins Correctional Centre (formerly Ararat Prison); transferred after Castlemaine closure
Truganina, Victoria, Australia
Nov 24, 2003 – Jul 23, 2013 · Port Phillip Prison; maximum security; questioned about other cold cases 2005; transferred to St Vincent's Hospital Melbourne secure ward July 2013 for terminal lung cancer care
CA
Victoria, British Columbia, Canada
1965 – 1966 · Khancoban · Remained after family moved to finish exams, lived with family of friend Ken Hosking; sexually assaulted two 6-year-old girls in 1965, no charges laid
Known Vehicles
Vehicles and approximate dates of ownership or use, as reported in the cited records. A photo next to a vehicle is the vehicle itself as published.
1967 grey station wagon – grey station wagon, plate EUU 786
approx. 1967 – 1969
Used in abduction and murder of Yvonne Tuohy 1969; witness Shane Spiller saw this vehicle and reported Navy insignia on it to police
Timeline
Sep 15, 1948
Derek Ernest Percy born in Strathfield, New South Wales to Ernest and Elaine Percy.
1964
At age 16, Percy begins stealing women's clothing from clotheslines ('snowdropping') and stabbing with knife; newspaper nicknames culprit 'snowdropper'; school begins to falter.
Dec 1964
Percy grabs and assaults Linda Slight at age 16.
1965
Percy sexually assaults two 6-year-old girls at Khancoban; no charges laid but is expelled from school and family moves.
Nov 25, 1967
Percy accepted into Royal Australian Navy with service number R66951, training as Electrical Mechanic.
Mar 09, 1968
Percy stationed to Sydney on aircraft carrier HMAS Melbourne.
Jul 01, 1968
Percy transferred to troop ship HMAS Sydney based in Melbourne.
Apr 01, 1969
Percy stationed on HMAS Cerberus naval base; attempts to abduct a 12-year-old girl riding a bike near the base but she escapes.
Jul 20, 1969
12-year-old Yvonne Elizabeth Tuohy abducted at knifepoint from Ski Beach near Warneet, Victoria; her body found 8km away with evidence of strangulation and mutilation; 11-year-old witness Shane Spiller escapes and reports vehicle description with naval insignia.
Jul 21, 1969
Derek Percy arrested at HMAS Cerberus naval base; found washing blood from clothes; initially confesses to Yvonne Tuohy murder.
Jul 23, 1969
Police take blood sample from Derek Percy.
Aug 01, 1969
Police search Percy's house; find no significant evidence except matching handwriting.
Apr 1970
Derek Percy committed to Aradale Mental Hospital (Ararat Mental Hospital) under Governor's pleasure.
Apr 02, 1970
Trial of Derek Percy begins at Supreme Court of Victoria before Justice A.F. Starke; Crown Prosecutor G.L. Kneale presents forensic and circumstantial evidence including bloodstains matching victim's blood type, fiber evidence, eyewitness identification by Shane Spiller.
Apr 07, 1970
Trial concludes; jury finds Derek Percy not guilty by reason of insanity.
Apr 10, 1970
Verdict entered: Derek Percy found not guilty by reason of insanity; sentenced to indefinite detention at Governor's pleasure pursuant to Section 20 of Victoria's Crimes Act; initially committed to Mont Park Psychiatric Hospital for evaluation.
Sep 28, 1971
Prison search finds pornographic writings, abduction blueprints, obscene notes, and complex charts showing abduction plots in Percy's cell.
Aug 01, 1986
Derek Percy transferred to Beechworth, a medium-security facility.
Sep 09, 1987
Derek Percy transferred to Castlemaine Prison.
Jun 1993
Derek Percy transferred to Ararat Prison (Hopkins Correctional Centre) after closure of Castlemaine.
1998
Governor's Pleasure law abolished; Derek Percy re-evaluated to determine if he should be released; experts agreed he should not be released.
2001
Derek Percy's father Ernest dies from Motor Neuron Disease.
Nov 24, 2003
Derek Percy transferred to Port Phillip Prison, Melbourne.
2005
Victoria Police investigators question Derek Percy about unsolved child murders including Linda Stilwell, Simon Brook, and Beaumont children; Percy claims he cannot remember details.
Jul 20, 2013
Derek Percy, terminally ill with lung cancer, questioned at his hospital bedside about Linda Stilwell's 1968 disappearance; he denies involvement.
Jul 23, 2013
Derek Ernest Percy dies from lung cancer at St Vincent's Hospital, Melbourne, at age 64, after 44 years in continuous custody; does not admit to any further crimes.
Sources
Solve the Case is never the original source. Each item below is the public record a statement on this page rests on, with an archived copy where one exists.
Other · Serial Killer Calendar ·
Serial killer, Derek Ernest PERCY“Percy was found not guilty on insanity grounds of the 1969 murder of Yvonne Tuohy, 12, who was snatched from Warneet Beach, southeast of Melbourne.”
Other · Murderpedia ·
Derek Percy“Declared not guilty by reason of insanity, he remains imprisoned because he is considered too dangerous to be released. He was committed to Ararat Hospital in April 1970.”
Other · Radford University Department of Psychology ·
Radford University serial killer biography: Percy, Derek“Jury finds Derek not guilty by reason of insanity. He is assigned indefinitely to prison as part of the Governor's Pleasure law designed to protect society.”
Other government record · Wikipedia ·
Derek Percy“Derek Ernest Percy (15 September 1948 – 23 July 2013) was an Australian convicted child killer who abducted and murdered 12-year-old Yvonne Elizabeth Tuohy from a beach in Warneet, Victoria, on 20 July 1969, for which he was found not guilty by reason of insanity and detained indefinitely at Aradale Mental Hospital.”
Other · Grokipedia ·
Derek Percy“Derek Ernest Percy (15 September 1948 – 23 July 2013) was an Australian convicted child killer who abducted and murdered 12-year-old Yvonne Elizabeth Tuohy from a beach in Warneet, Victoria, on 20 July 1969, for which he was found not guilty by reason of insanity and detained indefinitely at Aradale Mental Hospital.”
News report · ABC News ·
Child killer Derek Percy dies in hospital“Convicted child killer Derek Percy has died at St Vincent's Hospital in Melbourne, just days after being questioned by detectives investigating the death of a seven-year-old girl more than 40 years ago.”
Offender registry · Find a Grave ·
Derek Ernest Percy (1948-2013) Memorial“Derek Ernest Percy. Born: September 15, 1948. Died: July 23, 2013. Apprehended: July 1969. Found not guilty, by reason of insanity of the murder of Yvonne Tuohy 12, July 20 1969 and remanded Indefinitely.”
News report · NZ Herald ·
Derek Percy believed to be Australia's worst child serial killer“In 1970, Percy was convicted of Yvonne Tuohy's murder but found not guilty by reason of insanity.”
Court record · Human Rights Law Centre ·
In the matter of a Major Review of Derek Ernest Percy 2010 VSC 179“On 17 April 1970, Mr Percy was found not guilty of the murder of a 12 year old girl on the grounds of insanity. He was ordered to be detained until 'the Governor's pleasure became known' and remained in such detention until 1998.”
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