His modus operandi was to approach backpackers along the Hume Highway under the guise of providing them transport to areas of southern New South Wales, then take his victims into the Belanglo State Forest where he would incapacitate and murder them.

[4] The impoverished Milat family initially lived on a rural weatherboard cottage farm in Bossley Park, 36 kilometres west of Sydney, before relocating to Liverpool.

Many of the ten Milat boys were well known to local police and were used to handling knives and firearms, spending their afternoons shooting at targets in their parents’ yard.

He was rearrested in 1974 after his mother was taken to hospital suffering from a heart attack, but the robbery and kidnap cases against him failed at trial with the help of the Milats' family lawyer, John Marsden.

One case involved a young Victorian couple from Frankston, Deborah Everist, 19, and James Gibson, 19, who had been missing since leaving Sydney for ConFest, near Albury, on 30 December 1989.

[7] Similarly, a German couple, Gabor Neugebauer, 21, and Anja Habschied, 20, had disappeared after leaving a Kings Cross hostel for Mildura on 26 December 1991.

[7] A large knife had cut through his upper spine causing paralysis, and stab wounds to his back and chest would have punctured his heart and lungs.

[15] The presence of Gibson's body in Belanglo puzzled investigators as his camera had previously been discovered on 31 December 1989, and his backpack later on 13 March 1990, by the side of the road at Galston Gorge, over 120 kilometres (75 mi) to the north.

[21] In response, on 14 October 1993, Task Force Air, containing more than twenty detectives and analysts, was set up by the New South Wales Police.

[24] Speculation arose that the crimes were the work of several killers,[25][26] given that most of the victims had been attacked while as pairs, had been killed in different ways, and buried separately.

A few years earlier, on 25 January 1990, Onions had been backpacking in Australia and, while hitchhiking from Liverpool station towards Mildura, had accepted a ride south out of Casula from a man known only as "Bill".

[29][30] Onions flagged down a passing motorist, Joanne Berry of Canberra, and together they described the assailant and his vehicle and registration number to the Bowral police.

[5] Police soon learned that Milat had recently sold his silver Nissan Patrol shortly after the discovery of the bodies of Clarke and Walters.

[38] On 28 June, Milat sacked James Marsden, his family's lawyer, and sought legal aid to pay for his defence.

Milat's trial opened at the Supreme Court of New South Wales in Sydney on 26 March 1996 and was prosecuted by Mark Tedeschi.

"[41][42] His defence argued that, in spite of the evidence, there was no non-circumstantial proof Milat was guilty and attempted to shift the blame to other members of his family, particularly Richard.

[47] In November 1997, Milat appealed against his convictions due to a breach of his common law right to legal representation, as established in Dietrich v The Queen.

[55] On 26 January 2009, Milat cut off his little finger with a plastic knife with the intention of mailing it to the High Court of Australia to force an appeal.

[56] He was taken to Goulburn Base Hospital under high security; however, on 27 January, Milat was returned to prison after doctors decided surgery was not possible.

[60] On 9 August 2019, a terminally ill Milat was moved to a secure treatment unit located at the Prince of Wales Hospital following the loss of twenty kilograms in previous weeks; he was also exhibiting a high temperature.

[61] On 27 October 2019, Milat died from oesophagus and stomach cancer at 4:07 a.m. within the hospital wing at Long Bay Correctional Centre.

[62] Prior to his death, Milat wrote a letter to his family requesting that his funeral be paid for by the New South Wales government.

"Various strategies were deployed on each occasion, including different combinations of detectives and utilising recorded interviews with victims' families as an investigative technique," the statement said.

"[41] Although Milat died never having officially confessed, he is said to have previously admitted to his mother, with whom he had a close relationship, that he was responsible for the backpacker murders.

[65] State and territory-wide investigations into the unsolved deaths and disappearances of young persons were started in 1993 by Task Force Air by comparing Milat's known criminal and victim profile along with his known modus operandi to cold cases.

[65] Also, Milat was very geographically mobile as he started working as a truck driver in the mid-1970s, transporting tyres via Adelaide, Melbourne and Brisbane to Goulburn, Yass, Canberra and Perth.

Based on almost identical similarities in modus operandi, three unsolved murder victims were identified who task force commander Clive Small listed as having a high possibility of being Milat's victims:[66] Other cases of interest which were investigated included a series of unsolved disappearances of young women in the Hunter Region south of Newcastle that were originally thought to be the responsibility of a separate unidentified serial killer: Milat was only identified as a person of interest in the disappearances of Goodall, Hickie and Robinson in a 2001 inquest.

Milat, who worked as a road worker in the late 1970s, was of significant interest to the inquiry, according to state coroner John Abernethy, and had “definite links to the Hunter Region”.

Similarly, superintendent Clive Small, who led the investigation into the backpacker murders, also believed that Milat was responsible for the shooting of Knight.