The guard, Leigh Herewini (37), was the former partner of Broughton's aunt and would often take the 15-year-old on security rounds with him.
Yesterday, Broughton pleaded guilty at a pre-trial hearing in the High Court at Auckland to the murder of Ms Aim, a Scottish backpacker. He had been due to stand trial in Rotorua next week.
He also pleaded guilty to wounding a 17-year-old girl with intent to cause grievous bodily harm less than two weeks before he killed Ms Aim.
On January 5 last year, Broughton had turned up at Herewini's house after bashing the 17-year-old in the same street.
The girl had left a party and started walking when she became aware someone [Broughton] was lurking behind her.
Concerned for her safety, she sent a text message at 2.37am to a friend asking for help.
Broughton grabbed her around the waist, but she struggled and grabbed his wrists.
When she turned her back to Broughton, he struck her with a rock, causing her to fall.
After repeatedly hitting her with the rock, he stopped only to pick up her handbag.
The girl, who had 10 separate head wounds that required more than 30 stitches, managed to get up and stagger to a nearby house for help.
Broughton then went to Herewini's house, where Herewini helped stash the pink handbag Broughton had stolen from the girl.
He was also working the night Ms Aim was murdered and helped cordon off the scene.
In the Rotorua District Court on November 14, Herewini was charged with being an accessory after the fact to the wounding of the 17-year-old girl.
He was sentenced to five months' community detention and six months' supervision.
The case was not covered by the media because details of his part in the crime were suppressed for fear they would prejudice Broughton's pending trial. Suppression orders were lifted yesterday following Broughton's guilty plea.
Herewini testified against Broughton during a depositions hearing in September.
A summary of facts, released in the High Court at Auckland yesterday, said that, on the night of the first attack, Broughton and a highly-intoxicated friend left a party and went to Herewini's house nearby.
Herewini left to do his security rounds, but returned after about an hour and discovered Broughton had left his house.
The teenager arrived back a few minutes later with blood on his T-shirt, hands and one armpit.
He told Herewini he had been in a fight at a party and might have broken the "other guy's" nose.
Herewini took Broughton to wash his hands under a tap on the side of his house and washed his T-shirt in the washing machine, giving him another one to wear.
The pair went through the victim's handbag, which Broughton later told Herewini he had found on the footpath.
Herewini took $20 from the girl's wallet and gave the remaining $20 to Broughton, before hiding the handbag in a bush at the rear of his property. He then took the teenager home.
Police were in his driveway when he returned, after using a dog to trace from the scene of the attack.
Three days later, Herewini disposed of the handbag in scrub. He later took police to the location.
Broughton denied hurting the girl when Herewini asked him about it during a telephone conversation after the attack was publicised in the media.
On the night of Ms Aim's murder, Herewini was notified of an alarm going off at Taupo Nui A Tia College.
He called police after finding smashed windows at the school and an officer found Ms Aim lying unconscious nearby. Herewini helped the officer cordon off the area.
He told the Taupo Youth Court last year he spoke to Broughton later that day. He had told him a Mongrel Mob prospect called Bryan committed the crime. Broughton also told Herewini that "Bryan" had borrowed his bicycle.
The following day, Broughton showed Herewini the baseball bat used to kill Ms Aim.
"He went and got it from under the house," Herewini told the court. "It looked like it had blood on it."
Herewini said he felt uncomfortable when he saw it because "it could've been the bat that hurt the girl".
The security guard asked Broughton if he thought Bryan would turn himself in and Broughton said no.
A cousin of Broughton's said the pair were close.
"He gets on almost too good with Leigh. They drink together."
