Mert Ney: Killer filmed horror videos in aftermath of Michaela Dunn's brutal murder

Mert Ney pleaded guilty to murder last year. Photo / Supplied

A harrowing video taken by a crazed knifeman as he posed in front of the lifeless body of a young woman he had just slaughtered in Sydney's CBD has been played in court.

It came as Michaela Dunn's mother, Joanne, told a sentence hearing at the Supreme Court on Monday that justice would never be done for her "beautiful" daughter.

She sat just metres from Mert Ney, who murdered the 24-year-old in a merciless attack on August 13, 2019.

Ney's horrific killing of Dunn in a unit on Clarence Street was followed by the cowardly stabbing of survivor Lin Bo during a terrifying rampage that struck fear through the heart of the city.

Michaela Dunn, 24, who was fatally stabbed by Mert Ney in 2019. Photo / Instagram

On Monday the court was played disturbing footage taken by Ney on social media app Snapchat, which showed him posing in front of Dunn's body and revelling in her death.

In the video he raised a blood-soaked hand to point a finger toward the ceiling before leaning down to show the distressing scene.

Blood could be seen pouring from her body. Her arms were folded across her chest. "F*** infidels," Ney says.

Many of those in the packed gallery chose to leave the court before the video was played after being warned of its distressing contents by Justice Peter Johnson.

Michaela's mother was among those who remained.

In another Snapchat video taken as Ney fled through a fire escape, he scanned down his body to show the blood on his hands, pants and shoes before saying: "I actually f***ing did it."

CCTV footage played to the court showed the sheer panic he created that day as he ran through the streets with a knife outstretched, a balaclava covering his face and blood on his T-shirt yelling "Allah Akbar".

It captured the moment he stabbed Lin Bo in the back with a butcher's knife, with the court hearing she still lives in "constant fear and anxiety".

"I dropped like a hunted animal. Blood pouring from my side," Bo said in a statement read to the court on her behalf.

"I am still hugely afraid of the possibility of going back in the city where the attack happened."

Many people scattered out of the way as he bore towards them on the footpaths, but some brave souls were running toward him in dogged pursuit.

A milk crate was used to subdue Mert Ney. Photo / Seven News

Armed with chairs and items including a crowbar, office workers and firefighters were among the men who chased him for three minutes to bring the reign of terror to an end.

"You're going to Silverwater, c***," one man yelled after Ney was knocked to the ground, the court heard.

In documents before the NSW Supreme Court, prosecutors have described his reign of terror as "premeditated murder and mayhem".

In October last year he pleaded guilty to Dunn's murder and wounding with intent to cause grievous bodily harm for the attack on Bo. He faces life in prison.

Ney, now 22, was almost unrecognisable when he appeared in person on Monday before the King Street court where Joanne Dunn paid an emotional tribute to her "amazing" daughter.

The grieving mum recalled the moment she realised Michaela was not going to arrive for a pre-planned dinner at the family home the night she was murdered.

She first thought bad traffic was to blame for the out-of-character tardiness.

Michaela Dunn's mother has remembered her as a loving daughter. Photo / Instagram

With elder daughter Emily by her side in the witness box, who the court heard was Michaela's "best friend", Joanne Dunn fought through tears while listing all of the moments the family would now never share together.

Emily's wedding, where Michaela would have been the maid of honour, was one. The birth of her niece last year was another.

"Who would want to take the life of a gorgeous woman with the world at her feet?" she said.

"We have not just lost our daughter. But we have lost our future as it should have been. It seems so wrong that her perpetrator will continue on with his life at the end of his sentence."

Instagram photo of Michaela Dunn, 24, who was fatally stabbed by Mert Ney in Sydney's CBD on August 13, 2019. Photo / Instagram

Dunn said the media had been "extremely cruel" in their initial portrayal of her daughter – who was a sex worker – saying they stripped her of an identity.

"They had no idea of the amazing young woman she was," she said. "I want people to understand that Mikky could have been their daughter. Their sister, their friend. She was just the girl next door."

She thanked the "sidewalk heroes" who pursued and stopped Ney, saying they might have saved more families from her unimaginable grief.

In court Ney bore little resemblance to the man whose face had been etched into infamy. His cheeks were much fuller than on the day of Dunn's murder.

He was detained by members of the public about 2pm on August 13, 2019. Photo / News Corp

The 22-year-old wore a black suit jacket with no tie, his shirt was untucked and his thick, curly hair was shaved at the sides into a mullet.

He watched the videos, showing little emotion and at times rested his head on the palm of his hand as he slumped in the dock.

His sister Direnc Ney began to cry when she was called to the stand to give evidence in support of her brother.

Ney said her sibling called from prison regularly, sometimes every day of the week, and had expressed his remorse in a letter he wrote to her.

"He said he doesn't understand what happened that day. He's sorry he hurt people," she said.

The sentence hearing will continue today.