An Aboriginal woman has admitted murdering 22-year-old Newcastle man James Callahan, marking the first guilty plea in a case that shocked the Hunter region after police alleged the young environmental enthusiast was fatally attacked for telling a group of people not to litter.

The case returned to Newcastle Local Court this week, where 35-year-old Alivia Muriel Briggs appeared via video link from custody and pleaded guilty to one count of murder. Her sentencing will now be dealt with in the NSW Supreme Court, where a date is expected to be set in September.

While Briggs admitted responsibility for the killing, the remaining accused have continued to deny the allegations against them, setting the stage for what is expected to be a lengthy Supreme Court trial involving multiple defendants and extensive CCTV and mobile phone evidence.

James Callahan died after what police describe as a violent and coordinated attack on Beaumont Street in Hamilton during the early hours of November 17, 2024.

According to investigators, the confrontation began shortly after 2am when Mr Callahan and a friend were eating outside a kebab shop. Court documents allege he commented after seeing rubbish thrown from a vehicle, telling members of the group not to litter.

Police allege the seemingly minor disagreement quickly escalated into a violent confrontation.

Investigators claim Briggs exited the vehicle with several others before one member of the group allegedly kicked Mr Callahan in the face while he remained seated on the footpath.

Although Mr Callahan and his friend then walked away from the scene, police allege the confrontation did not end there.

Instead, investigators claim two vehicles followed the pair before they were ambushed moments later in what prosecutors allege was a deliberate and coordinated attack.

Police allege members of the group shouted threats including “smash him” and “kill him” while Mr Callahan was repeatedly assaulted.

Authorities further allege Briggs stabbed the 22-year-old in the chest while another accused, Frank Allen, struck him with a metal pole.

Police also allege Briggs’ brother, Ryan Sampson, later arrived at the scene, jumped from another vehicle and stabbed Mr Callahan several times in the back and neck after first attempting to attack his friend.

Emergency services rushed Mr Callahan to hospital, but despite medical efforts he died from his injuries.

The prosecution alleges the group then fled the scene in three separate vehicles.

The alleged attack was captured on CCTV cameras as well as graphic mobile phone footage that later formed a significant part of the police investigation.

Strike Force detectives subsequently arrested multiple people in connection with the killing as investigators pieced together the movements of those allegedly involved.

During Wednesday’s court proceedings, Briggs became the only accused person to admit guilt.

Her brother, Ryan Sampson, pleaded not guilty to murder and to a charge of using an offensive weapon in company to commit an indictable offence.

Police continue to allege that both Briggs and Sampson inflicted fatal stab wounds during the attack.

Frank Allen, Jason Talbot and George Fernando each pleaded not guilty to murder.

Diane Fernando pleaded not guilty to murder as a principal in the second degree, reflecting allegations that prosecutors say relate to assisting or encouraging the commission of the offence rather than directly carrying out the fatal attack.

A sixth accused, Teelah Cooper, also remains before the courts.

Cooper has been charged with being an accessory after the fact to murder after police alleged she assisted Sampson in avoiding arrest following the killing.

Her matter has not yet proceeded to a plea because aspects of the prosecution facts remain disputed.

She is scheduled to return to court next month.

Cooper’s bail history has attracted separate attention during the proceedings.

She was initially granted bail before authorities alleged she breached strict conditions by communicating hundreds of times with Sampson despite being prohibited from contacting any co-accused.

Following those alleged breaches, her bail was revoked after she surrendered to police.

Several months later, however, the NSW Supreme Court granted her bail again after considering factors including her lack of criminal history, strong family support within the Indigenous community and documented mental health conditions, including PTSD, anxiety, depression and adjustment disorder.

The prosecution case is expected to rely heavily on witness accounts, surveillance footage and forensic evidence gathered after the attack.

According to court documents, investigators allege the confrontation escalated from a verbal exchange into a sustained pursuit that continued even after Mr Callahan attempted to leave.

Police argue the evidence demonstrates the alleged assault was not confined to a spontaneous street fight but developed into a deliberate ambush involving several individuals travelling in multiple vehicles.

Defence lawyers representing the remaining accused are expected to challenge various aspects of those allegations when the matter eventually proceeds to trial.

As the criminal proceedings continue, many details surrounding the incident remain before the courts and have yet to be tested before a jury.

The guilty plea entered by Briggs resolves only her own criminal liability and does not determine the guilt or innocence of any of the remaining defendants, each of whom continues to be presumed innocent unless proven guilty.

The death of James Callahan prompted an outpouring of grief throughout Newcastle.

More than 100 family members and friends gathered at Stockton breakwall to farewell the young man, who was remembered as an avid fisherman and passionate environmentalist with a deep appreciation for nature.

His parents described him as kind, caring and compassionate, while his mother, Sally Callahan, spoke publicly of her struggle to understand why her son had become the target of such violence.

“I just can’t make sense of it,” she said following his death.

The case has remained one of the Hunter region’s most closely watched homicide prosecutions because of the large number of accused, the alleged sequence of events captured on video and the circumstances surrounding what investigators say began as a dispute over littering.

The Supreme Court is expected to revisit the matter in September, when Briggs’ sentencing timetable will be addressed and trial dates for the remaining accused are expected to be confirmed.

Until those proceedings conclude, significant aspects of the prosecution case remain subject to determination by the courts.