Cassius Turvey murder trial and sentencing court case

The Supreme Court of Western Australia has handed down murder sentences to the killers of 15-year-old Aboriginal boy Cassius Turvey to life imprisonment, bringing a measure of justice to a murder case that shocked the nation.

Cassius died after being brutally assaulted on 13 October 2022 while walking home from school in Middle Swan, Perth. The attack followed several days of escalating violence involving a group of adults who had been roaming local streets looking for teenagers they believed were responsible for earlier disputes.

Twenty-one-year-old Jack Brearley and his then partner, Aleesha Gilmore, 20, were living together at Gilmore's father's home on Mockeridge Circuit in Middle Swan. Brearley worked only intermittently as a bricklayer and supplemented his income by selling cannabis. Gilmore worked at a local early learning centre.

The pair's relationship was described in court as volatile. They socialised with several others who later became involved in the offending: 27-year-old Brodie Palmer, who supplied cannabis grown at his parents' property in Wundowie; 24-year-old Mitchell Forth, a long-time friend of Brearley; and 18-year-old Ethan Mackenzie, the youngest member of the group. The court described both Forth and Mackenzie as followers of Brearley.

Violence Begins

The events that culminated in Cassius Turvey's death began on 9 October 2022.

That afternoon, Gilmore received a call from her younger brother Cody, who said he had arranged a fight with another boy at Talbot Road in Jane Brook. When Cody arrived, more teenagers appeared than he expected. Believing he might be "mobbed", he and his friends fled the area and called Gilmore for help.

Gilmore, Brearley, Forth and Mackenzie drove to Jane Brook and picked Cody up. They then began driving around the area looking for the group of boys they believed had threatened him.

Instead, they encountered a 14-year-old boy identified in court as "SM", who was walking along the road. Gilmore stopped the car, got out, and ordered him to get inside. Mackenzie also exited the vehicle holding a knife about 30 centimetres long. Fearing what might happen if he refused, SM got into the car.

First Assault and Abduction

The group continued searching for the teenagers they believed had threatened Cody. They eventually encountered another group of boys, including a child identified as "BT", who had come to the area for an unrelated fight that had already been called off.

Brearley, Forth and Mackenzie jumped out of the car and chased the group. BT tried to hide in nearby Dagmar Way, but the three men caught him. CCTV footage later captured much of the attack.

Brearley struck BT first, punching him in the head and knocking him to the ground. The three men then kicked and punched him repeatedly. Mackenzie also stabbed toward the lower part of BT's ribcage with the knife, leaving a wound that later became infected.

BT was dragged down the street and forced into the car, which was now being driven by Gilmore. Witnesses later described him as having "blood all over him".

Both BT and SM were taken back to the Mockeridge Circuit house. BT later told the court he was given a Nintendo Switch — which the judge found was intended as a bribe to discourage him from reporting the assault. When the group eventually dropped him home, they warned him not to tell anyone what had happened.

Escalating Tensions

Three days later, on 12 October, several school-aged children went to the house and smashed windows of Brearley's Kia Rio parked outside. The court accepted the damage may have been retaliation for the earlier assaults, though there was no evidence that SM or BT were involved.

Enraged, Brearley and Forth began searching for the person responsible. Brearley came to suspect a boy known as "NB", largely because the child had been seen riding his bike in the nearby suburb of Stratton.

NB's mother worked with Gilmore at the same early learning centre. Brearley and Forth confronted her at her workplace and demanded she pay for the damage, triggering an argument between the two women. Gilmore was subsequently dismissed from her job.

The Day of the Killing

On the afternoon of 13 October 2022, Brearley, Palmer, Forth and Gilmore drove to Palmer's home in Parkerville, where they spent about 40 minutes drinking.

Gilmore then received another call from her brother Cody, claiming he was again being threatened with violence.

The court later found that a fight had indeed been arranged between the Gilmore brothers and two other boys, but that the others had already left the meeting point after the Gilmores failed to appear. The judge noted it was possible Cody exaggerated the threat in order to draw the adults into the situation.

Brearley, Palmer, Forth and Gilmore returned to Mockeridge Circuit. Palmer brought knuckledusters with him. Witnesses later heard the group discussing the weapons and preparing for a confrontation. Brearley and Forth broke metal poles off shopping trolleys to use as makeshift weapons before driving around the area looking for the boys they believed were responsible.

Why Did Cassius Turvey Get Attacked?

Around the same time, students from Swan View Senior High School and Governor Stirling Senior High School had caught a bus from Midland train station and got off along Lloyd Street in Middle Swan. Among them was 15-year-old Cassius Turvey.

The court found none of the students had any involvement in the earlier vandalism.

Brearley's group drove past the teenagers. After a brief argument inside the car, Gilmore got out and left the others. Palmer then drove back toward the group of students and parked.

Brearley and Forth got out of the car, yelling accusations about the smashed windows. Brearley was carrying one of the metal trolley poles.

He swung the pole at one teenager, narrowly missing his head. Some of the children ran away. One student handed a knife to another boy so he could protect himself and the group.

Brearley instead turned toward a smaller child on crutches, identified as "TB", striking him in the face with the pole. TB fell to the ground, losing his crutches and hat. Forth took both items and placed them in his vehicle.

Who Killed Cassius Turvey? Cassius Turvey Murderers

Many of the students fled. Brearley, Forth and Palmer first chased them on foot and then pursued them in their car.

Brearley leaned out of the vehicle window, still holding the metal pole, shouting racial abuse as the group drove after the fleeing children.

Eventually Brearley and Palmer caught up with Cassius Turvey near a creek as he ran toward the local TAFE campus.

As Cassius attempted to flee, Brearley struck him in the head from behind with the metal pole. The blow knocked him to the ground.

Brearley then raised the pole above his head and repeatedly brought it down onto the teenager's head. The attack was witnessed by numerous children who had been running with Cassius.

What Happened to Cassius Turvey? Cassius Turvey Injuries

The assault caused catastrophic injuries.

Cassius's right ear was split completely in half. He suffered a deep wound across his forehead and severe internal brain injuries, including a subdural haematoma and bleeding inside the brain.

Although he was initially discharged from hospital, his condition deteriorated rapidly. Despite emergency surgery, Cassius Turvey died on 23 October 2022.

His death triggered widespread public outrage and vigils across Australia, becoming a symbol of the dangers of racial violence and youth intimidation.

Joint Criminal Enterprise

The doctrine of joint criminal enterprise (JCE) deems everyone who has participated in group criminal activity liable for agreed offences as well as any offence that must have been in mind as essential to advancing the agreed offence, irrespective of the part they have played, provided they had the requisite intention. This is done by attributing the acts of all participants to each other.

The doctrine was confirmed in the case of Johns v The Queen (1980) 143 CLR 108. There have been a number of subsequent High Court of Australia cases which have refined and shaped the doctrine and clarified its application. In 1980, Johns confirmed the application of the doctrine in its modern form, and confirmed the test was subjective in nature, reflecting the law's change to favour a subjective inquiry into the mind of the accused. In April 1985, the High Court set out the test for determining the scope of the agreement in Giorgianni. The Crown is required to show: (1) subjective knowledge of the essential facts which constituted the offence agreed to; and (2) intentional participation in a crime by lending assistance or encouragement.

The rationale for this doctrine was explained recently in Mitchell and ors v The King (2023) 97 ALJR 174, 183 [54]. Those who contribute to the commission of a criminal offence will be held liable irrespective of the part they have played. The Crown should not be required to establish which party to the agreement committed which specific component of the offence before a conviction can be sustained against the individual members who acted in agreement. This is because all the acts were all committed with the authority of each of the other group members.

Mr Brearley and Mr Palmer were convicted of murder on this basis, receiving life sentences. Both were found to have the intention to kill or cause grievous bodily harm, and Mr Brearley's actions were attributed to Mr Palmer under the doctrine of JCE.

Mr Brearley was handed a non-parole period of 22 years, and Mr Palmer a non-parole period of 18 years.

Extended Joint Criminal Enterprise

The doctrine of extended joint criminal enterprise (EJCE) attributes liability for additional offences, beyond the scope of a joint criminal enterprise, to all those participants who foresaw the possibility of additional offences being committed and nevertheless continued to participate. The secondary participant to the enterprise does not need to agree to the commission of the incidental offence before being held liable for it. In fact, they will be held liable even if they had expressly rejected the proposition of the incidental offence being committed.

The doctrine was imported into Australian law from the UK in the case of McAuliffe v The Queen (1995) 183 CLR 108. There have been several High Court of Australia cases which have clarified and reaffirmed the application of the doctrine since its importation into Australian law. In November 2003, Gillard provided an opportunity for the application of the existing common purpose principles to a complex scenario. In 2006, the High Court in the case of Clayton rejected an attempt to abolish the doctrine of extended joint criminal enterprise. In February 2016, the Supreme Court of the United Kingdom in Jogee abolished the doctrine of extended joint criminal enterprise first confirmed in Chan Wing-Siu in 1985. In August 2016, the High Court of Australia in Miller v The Queen (2016) 259 CLR 380 entertained arguments asserting that the principle of extended joint criminal enterprise should be abolished in Australia, following the abolition of the doctrine in the United Kingdom. The High Court did not accept the doctrine of extended joint criminal enterprise should be abolished, confirming that it continues to form part of Australian law, despite the divergence of the law in the United Kingdom.

Under the doctrine, if participant A agrees to commit a dangerous offence which may involve violence less than grievous bodily harm, and participant A foresees that another participant may commit an unlawful and dangerous act but not with an intent to kill or cause grievous bodily harm, participant A is guilty of manslaughter, while the participant/s who acted with an intent to kill or cause grievous bodily harm are guilty of murder. This application of the principle was clarified in the High Court case of Gillard v The Queen (2003) 219 CLR 1, 24 [62].

It was on this basis that Mr Forth was convicted of manslaughter. The conviction reflects a finding by the jury that Mr Forth did not have the requisite intent necessary to sustain a murder conviction but did foresee that Mr Brearley or Mr Palmer would commit an unlawful and dangerous act falling short of an intent to kill or cause grievous bodily harm. Mr Forth received a 12 year sentence, with a non-parole period of 10 years.

Under the common purpose doctrines there is a narrow pathway to acquittal of both murder and manslaughter. Participant "A" and participant "B" agree to commit a dangerous offence which may involve violence less than grievous bodily harm. "A" does not foresee that "B" may act with an intent to kill or cause grievous bodily harm. "B" goes completely beyond the scope of the agreement, beyond what a reasonable person in "A's" position could have suspected, resulting in death. "A" is not guilty of murder or manslaughter.

It was on this basis that Ms Gilmore was acquitted of murder and manslaughter. The acquittal reflects a finding by the jury that Ms Gilmore's intent was more likely to be to rough up the victims and formed on the wrongful understanding that she needed to stop a fight between her brother and the other children. Ms Gilmore received a 15-month prison sentence, suspended for two years, with strict community conditions including supervision and a curfew for her participation in the other offences in the lead up to Cassius's murder.

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