The Crown alleges Fane and his late brother Anthony Fane killed the two men after Anthony believed Lasslett was having an affair with his partner, Jessie Lee Booth.
Booth was found dead at a Brookfield address on February 14, 2020 - the day after Anthony Fane was shot dead by police.
Police believe Anthony Fane killed her on or around February 9.
The defence argues Anthony Fane was solely responsible for the shootings two days later.
Te Poono, who is Tarei's older brother, told the jury in February last year that he was living with his partner and daughter in Lonsdale St New Brighton, Christchurch.
He said on February 12, 2020, he got a Facebook call from Tarei asking if it was okay if she, Fane and their child came to visit for a holiday, and he replied "sweet as".
Te Poono said they arrived after lunch the next day with Tarei driving her silver Toyota and Fane seemed quite "normal".
Later that afternoon they ended up in the spare room playing PlayStation games, including Mafia and Grand Theft Auto.
Crown solicitor Anna Pollett asked Te Poono whether he had any discussions with Samuel Fane about why they were in Christchurch and about the shootings.
Te Poono said not at first but about 5pm that day they ended up in the spare room alone and were chatting as he continued to play Grand Theft Auto.
He said Fane asked him whether he had seen the news and mentioned the shootings then told him that it was "Pants" who was responsible for both men being shot.
Te Poono said Samuel told him that Pants [Anthony Fane's nickname] had found out Paul Lasslett had been stepping out with Booth and he had gone over to the "dude's house" to "shoot him up".
Samuel Fane also told him his brother Anthony did it after he "cracked the code".
Te Poono claimed he did not even know what Anthony Fane looked like.
"Samuel was talking to me, but I was only half-listening as I was still playing on the Play Station and hoping he would get the hint to stop talking," he said.
Te Poono said Fane told him that he had gone for a ride with his late brother and was there when the two men — Lasslett and Littlewood — were shot.
Pollett reminded the witness in a recorded statement to police on February 15 last year he told a detective that the accused told him "they" had carried out the shootings.
The jury heard that Te Poono told the officer that Fane had confirmed to him that he and his brother Pants "stormed over" to "see that [Lasslett] fella" and "they killed them".
"You told the police Samuel told you they stormed over to there to sort him out and they shot them... these were your words," Pollett said.
Te Poono said he could not recall "word for word" what he was told by the accused.
He also suggested that the police had "made him say" what he did in the signed recorded statement because they did not like his first statement.
Te Poono said it was not exactly what he meant in his signed statement.
"I should not have worded it that way," he said.
Pollett asked why would Samuel Fane have insisted on going along with his brother then.
"To help his brother out," Te Poono replied.
"I told Samuel a few times he should hand himself in... He also told me Anthony was going to go out in a blaze of glory and take some pigs [police] with him."
Te Poono said when asked why Fane had brought the shotgun down with him, Fane told him he was thinking about selling it.
The double murder accused later told him his brother "Pants" got shot and died, he said.
"I asked him, what are you going to do now? But he was too busy crying for his brother."
The jury also heard some agreed facts read by Crown prosecutor Justine Sutton.
This included police locating a sawn-off 12 gauge shotgun and a spent shotgun cartridge inside a bag at Te Poono's Lonsdale St home during a search after Fane's arrest.
The shotgun, the spent cartridge and Fane's clothing were forensically examined but there were no bloodstains or trace elements of DNA found on the items, the jury heard.
Also found in the house was a Countdown receipt for some razors and other items, and in the bathroom was a used razor and some black hair that matched Fane's shaven head.
In the boot of the silver Toyota were a black leather logo vest and a white long-sleeved T-shirt with the logo Mangu-Kaha Gangstaz.
A cut down .22 rifle was found in the footwell of Anthony Fane's black Ford Falcon after he was fatally shot by the police.
The trial continues today — May 18.
