Lawyers for four people accused of murdering an 18-year-old man on the outskirts of Darwin two years ago, have used closing arguments to accuse prosecutors of "cherry-picking" from disjointed and contradictory evidence from intoxicated witnesses.

Kingsley Alley was found dead by police on the morning of October 8 in the driveway of a vacant residence in Palmerston, with police investigators later finding he bled to death from a stab wound to an artery in his arm.

For the past four weeks, the Northern Territory Supreme Court has heard evidence from more than 40 witnesses in the trial of four people accused of his murder, with lawyers for the Crown and all co-accused this week making their closing submissions to the jury.

In his final address, Crown prosecutor James Moore said Madison Butler, her mother Melissa Clancy, their "associate" Dechlan Wurramarra and another man, who cannot be named for legal reasons, had formed a "common purpose" to kill Kingsley Alley in the early hours of October 8, 2022.

"Who did the specific act, or acts, which caused the death and at what particular time? We don't need to prove that," Mr Moore said.

"It's all about the common purpose, they were linked in purpose and had the same agenda."

Each of the four accused have rejected that proposition via their defence lawyers, who told jurors that evidence from three key witnesses to the alleged killing was "incomplete and unreliable".

The court has heard Mr Alley threw a drink on Ms Butler outside a party that morning in 2022.

Witnesses at the party testified that Ms Butler was "upset and angry" when she called her mother, Ms Clancy, telling her to come and pick her up, along with the unnamed co-accused.

At about 2am, a car driven by her father Lesley Butler — who is not accused of any wrongdoing — with Ms Clancy and Mr Wurramarra as passengers, arrived to collect the pair.

Mr Moore told the court the group then forged an alleged "payback" plot to pursue Mr Alley and kill him.

"They each wanted to get revenge, they each rushed out of the car to attack him, they each had different weapons at different stages," he said. 

Ms Butler's lawyer, David Hallowes SC, said the prosecution's theory of the thrown drink as the motive for the fatal bashing was “extreme".

He said prosecutors had relied on a witness statement that Ms Butler aggressively threatened to "get" Mr Alley, over that of another witness more sober at the time, quoting from a Simon & Garfunkel song to make his point.

"A man hears what he wants to hear and disregards the rest," he said.

Colin Rogan — who was in the front seat of the car that morning, and is also not accused of wrongdoing — told the court once the group spotted "the young fella", all four co-accused got out, removed metal poles from nearby roadworks and attacked him.

"You could hear a bit of a commotion, swearing and carrying on and fisticuffs and the twanging of those pipes," he said.

"It was late at night, I was drunk as a monkey, I'm trying to remember all of this and I'll probably never forget it."

Despite Mr Rogan's testimony, both the prosecution and Ms Clancy's defence said Ms Clancy had a broken foot and remained inside the car throughout.

Her charges stem from allegations she participated by screaming out from the car for the others to kill Mr Alley.

But her lawyer, David Edwardson KC, told the court Ms Clancy's involvement in the murder was a fiction.

 "We know that Melissa Clancy was seated directly behind Colin Rogan and the Crown says she was screaming 'kill him, f***ing double-bank him all of youse'," he said. 

"If she did scream … she would've been screaming in his earhole and yet [Mr Rogan] says nothing of it."

Prosecutors suggested audio captured on CCTV recorded two different male voices — which they alleged belonged to the two male co-accused — saying "stab him" and "I'm going to stab you again, brother".

But the men's lawyers both told the court the audio was of such poor quality it was impossible to individually identify anyone or even prove what was said.

Meanwhile, Mr Wurramarra's barrister, Jon Tippett KC, said his client was acting in self-defence when he delivered the fatal stab wound to the underside of Mr Alley's arm.

Mr Tippett said Mr Alley had attacked Mr Wurramarra with a broken whiskey bottle and Mr Wurramarra had delivered a single defensive blow in response, without realising it would be fatal.

"Who would ever have thought that an injury under the arm or the armpit, could be so tragic?" Mr Tippett asked the jury.

"It was a shambolic event that was spontaneous [and] pregnant with stupidity and ignorance, and it is just incredibly sad that a young man died," he said.

Justice Peter Barr is expected to deliver his instructions to the jury on Monday before they begin their deliberations.