The squad was called to the Hastings home the man shared with his mother after she had called with concerns about her son's behaviour and mentioned there was a gun in the house.
The man came out of his house and was yelling aggressively and wearing boxing gloves, but complied with police and was restrained and handcuffed with temporary plastic cable ties.
The squad member had been tasked with reading the man his rights which he did while applying pressure to his back with his left hand to keep him there.
The constable had slung his rifle to his right side, after checking the safety catch was on, enabling him to kneel.
On standing, he returned the rifle back to his front. He did not recheck the safety catch as he had already ensured it was in the safety position. Usually a click could be heard when the safety catch was moved. During his evidence, the officer said he had not heard anything.
"I've gone forward a little basically, tilted a little bit, that's when I heard the bang," he said.
He said he did not realise it was his rifle that had discharged at first, usually smoke or a flash could be seen, "I don't remember seeing anything".
The court heard from fellow squad members, police and forensic scientists who described events leading up to the unintentional discharge. A national forensic scientist took a rifle from a fully suited AOS mannequin which had been rolled into the court room for evidence and demonstrated how the weight of the gun was such that if the switch rubbed on something it could be flicked from the safety setting to fire setting.
Erin FitzHerbert and Ben Vanderkolk led the crown's case, saying the constable failed to consciously ensure the rifle was safe and that he should have rechecked the safety catch, ultimately preventing the unintentional discharge.
When opening their case on day one, Mrs FitzHerbert told the court this was a police shooting a member of the public, "it's controversial, it's emotional, it's even frightening".
"He did not deliberately shoot the man, but he was careless. He was unexpectedly shot while he was lying on the ground."
The crown argued the constable was well equipped for his role, the callout was controlled and the environment was safe, "nothing was left to chance", and he had failed to maintain safety.
In defence, the constable's lawyer Jonathan Krebs said his client had not received the training he needed to adequately equip him for the front line.
"In a way he was unintentionally set up.
"The armed offenders' squad was short staffed, it seems corners were cut."
While on the stand the officer told the jury he had been to only about six AOS callouts and had attended only as many training days before the shooting. He was unclear about the types of ammunition used and had never had one-on-one tutoring.
Mr Krebs said the man who was shot should be compensated in some way by the police.
On day one of the trial the officer was seen approaching the man he had accidentally shot, they shook hands and briefly exchanged words.
There was blanket suppression in place during the trial. Suppression will be lifted for the constable's name at 4pm today unless an appeal for permanent name suppression is lodged.
