Witnesses said he made several attempts to steal other people's cigarettes and alcohol, and was asked to leave multiple times.
Whanga-Elliott was even escorted from the address several times but each time came back, Dunn said.
At one point he was physically removed by the partner of one of his aunties, Talosage Terry David Moreli.
Whanga-Elliott eventually left the party and went to his uncle's home, then returned to the party with a group of people in a car.
"Upon arrival they were met by a large group of people," Dunn said.
Moreli approached the vehicle and attacked the driver and Whanga-Elliott, kicking him in the shin and arm.
He was later charged with two counts of common assault for the attack, but was convicted and discharged. He was not believed to be responsible for Whanga-Elliott's death.
The group in the car fled the scene after the beating.
Witness statements varied after that point, but police believe Whanga-Elliott jumped out of the car, intending to go back to the party and fight.
Factors such as his injuries, damage to his clothing, witness accounts, and CCTV footage support this, Dunn said.
A 15-year-old witness who was in the car at the time and was intoxicated told police he remembered trying to hold onto Whanga-Elliott to stop him from jumping out.
The boy described being "extremely upset" at the time, telling the driver to stop, but remembers being told to "shut up" as the car continued moving, Dunn said.
The driver admitted to police he was intoxicated at the time of the incident.
He said Whanga-Elliott was talking about wanting to go back and fight, but in a later interview with police he said he may not have stopped the car at all, and that Whanga-Elliott might have gotten out of the car while it was still moving.
Another witness in the car said Whanga-Elliott jumped out of the car and landed on the grass before getting back up and walking back towards the party.
Police have ruled out this account, which is not supported by CCTV footage. The footage does not show Whanga-Elliott walking back towards the party.
Shortly after 3am, another driver and her passenger found Whanga-Elliott lying in the gutter with critical injuries. The passenger told police he was lying with his head and neck at "strange angles".
CCTV footage did show two men running after the car when it first fled the scene, and someone was thought to be carrying a piece of a white picket fence, but the timeframe was not long enough for the men seen chasing the car to reach the scene where the members of the public found Whanga-Elliott lying on the ground.
The piece of fence did not have any of Whanga-Elliott's DNA on it, Dunn said.
When asked at the inquest by Whanga-Elliott's mother if anybody would be charged over him falling from the car, Dunn said it was too late, because charges laid under the Land Transport Act had to be laid within six months of the offending.
Dunn also said there were no evidential breath or blood tests taken, so it could not be proved that the driver was drunk, and they could not prove he knew Whanga-Elliott had fallen out of the car.
Moreli also gave evidence at the inquest, where he described the events of the night.
When answering questions from Whanga-Elliott's mother, Moreli said the death had impacted his life.
"I will be affected by this for the rest of my life, I took a spiral downwards," he said.
"I knew Jardin personally, to the point where at times he has called me uncle.
"He was a bright kid."
Moreli described Whanga-Elliott as a "really humble" person with a "lovely nature".
He said he would "definitely" be friends with him if he was still alive.
The inquest is set to continue for the next two days.
