Gladstone, his friend and workmate, is being tried alongside him on a charge of recklessly discharging a .22 rifle during the same incident.
Cooper claims he acted in defence of himself, three other adults and seven children who were under threat from Mr Tauhore when he stormed his rural property at about 7pm on February 16 last year with a cohort of gang members.
Gladstone claims he was trying to warn the gang off and did not aim the .22 at anyone.
The family of Mangu Kaha gang boss Mr Tauhore yesterday marked the first anniversary of his fatal shooting.
On day one of the trial, prosecutor Rebecca Guthrie opened the Crown case by saying the entire incident had its genesis in a dispute between Gladstone and Mr Tauhore's partner, Noleen Brooking, at a horse sports event two days earlier.
Ms Brooking had tried on behalf of Gladstone's partner, her cousin Mary-Jane Waitoa, to get car keys from Gladstone, who was intoxicated.
But as the trial progressed, evidence from various witnesses, including comments Gladstone made in police interviews, showed there were greater, long-standing tensions between him and Mr Tauhore.
Gladstone spoke of once getting into "a big fight with some Mongrel Mob members", which had angered Mr Tauhore, who came over the next day and told him he was trying to make him look stupid.
During another altercation with him, Gladstone claimed Mr Tauhore said to one of his colleagues, "give me that f****n gun, I'm gonna shoot this young fulla myself".
Gladstone said he managed to flee.
Yesterday Steve Manning closed the Crown case against Cooper and Gladstone. Cooper's counsel Russell Fairbrother also made a closing address.
Gladstone's counsel, Tiana Epati, was expected to deliver her address this morning, to be followed by Justice Robert Dobson's summing up.
Mr Manning said the facts of the case were largely incontrovertible.
It was easy to excite prejudice in the case with just the mention of a gang. But this was really inter-whanau -- a family dispute and nothing more than a "silly squabble" over Gladstone's drunken comments at the horse sports event.
Mr Tauhore (who Gladstone described as having dreadlocks and a tattooed mask) had the potential for intimidation by his look and his gang involvement, Mr Manning said. But the jury had to consider him in a wider context.
He was also a father, partner, brother and no doubt a friend.
Prejudice could derail how the jury approached the case and Mr Tauhore was not here to speak for himself.
Equally, jurors had to be mindful of defence efforts to assert Cooper was a good person. He clearly was, but "where does that take you? That a good person shot a bad person so let's not bother with a trial?"
Jurors had to look past the emotion wrapped up in comments about Cooper's character and take a clinical view.
Had Cooper and Gladstone acted reasonably in the circumstances they believed existed at the time?
Was the force Cooper used reasonable? That was for jurors to decide, not Cooper.
"You might think killing another human being with a high-powered rifle from a relatively short distance (about 40 metres away) was probably the most lethal force that a person could use -- especially when the person shot is unarmed and the person doing the shooting is not the subject of the other's threats," Mr Manning said.
"The question is whether that extreme reaction was necessary in that circumstance."
Jurors also needed to consider whether Cooper intended to shoot Mr Tauhore, Mr Manning said.
If he intended to shoot and the shot caused death, then that was killing someone by an unlawful act -- at the very least manslaughter. If self-defence was excluded, then it became murder.
He knew Mr Tauhore was looking for Gladstone and that Gladstone was the target of his anger -- not him.
When Mr Tauhore arrived, Gladstone was already up a hill with the .22. He could look after himself. There was no need for Cooper to have done what he did.
Cooper and Gladstone were clearly expecting Mr Tauhore, so why didn't they take a different course of action?
They could have gone across the road to enlist the help of "a very sensible social worker", Mr Manning said, alluding to Cooper's mother-in-law who gave character evidence for the defence.
Why didn't Cooper fire a warning shot? A witness saw him take aim -- evidence that Mr Fairbrother said in his closing was unreliable.
Jo Davoren, the vice-president of Mangu Kaha, who gave that evidence, wrongly described the appearance of the gun. His evidence and that of fellow gang members Jason Tipene and Frank Kapua, was evasive, Mr Fairbrother said.
Even on the night their boss was shot, the gang had given police false information and they were still giving false information. One of their number, Sidney Rutene, who was to have given evidence, "clearly couldn't make it to court".
"What's that about? What's the point in hiding?"
Mr Fairbrother said, by contrast, the evidence for the Crown from others with Cooper during the incident was truthful.
Cooper was someone with good family and social values. He had integrity and loyalties to good people -- "every value that I hope you have and I hope that I share", Mr Fairbrother said.
"Jurors needed to consider what took a man who could be sitting alongside them, a sober, hard-working man who was careful with money, to being charged with murder?
"Something really serious must have happened. It wasn't a case of Cooper acting out of character -- it had to be something extraordinary. In little over an hour, his situation had gone from having a relaxed cup of tea in a peaceful rural setting after a hard day's work and a 4.30am start, to chaos and acute fear.
"Mr Tauhore was not unarmed. He might not have been packing a gun in each holster but he was armed with his back-up men -- flamboyantly dressed in their "colours" and willing to blindly follow their leader into any situation.
"There was no egress off the property for the group at the house. They couldn't ring anyone. Attempts had already been made to contact police. Cooper's lifestyle was such there was no locks on his windows and doors. It was not satisfactory for police to have suggested they lock all the doors and hide in wardrobes. The family was not supported in that isolated environment.
"Cooper used the only weapon available to him -- a gun brought there by a friend earlier that evening to shoot a horse. He believed he had fired a warning shot. The only person injured was the generator of the fear.
"He was a family man reacting to an urgent situation in the face of a primal fear. Women and children were screaming, gang members were advancing and Gladstone was firing shots, which only encouraged them.
"After the shooting, Cooper came forward without a bone of deceit. He took responsibility and the law was here to protect him because of the marvellous instrument that recognised that people could be put in vulnerable situations and sometimes act in ways that were not the most prudent but can only be considered inappropriate where there was evidence to support it."
Mr Fairbrother told jurors Cooper was a believable, decent man. He felt privileged to represent him and there was no one more deserving of a not guilty verdict.
- Gisborne Herald