A police officer has described the moments before and after he was allegedly shot in the head during an armed siege.

Regan Mauheni was felled by gunfire during the siege at Onepu Springs Rd on March 9 last year - an event he revisited for a jury in Hamilton on Monday, during the High Court trial of Rhys Richard Ngahiwi Warren.

Warren, 28, faces two counts of attempted murder, three counts of using a firearm against a law enforcement officer, and one of wounding with intent to cause grievous bodily harm.

MARK TAYLOR/STUFF Rhys Warren is charged with two counts of attempted murder, three counts of using a firearm against a law enforcement officer, and one of wounding with intent to cause grievous bodily harm.

The Crown alleges the four officers - Constable Mauheni, Constable Damian White, Constable Andrew Flinn, and Sergeant Logan Marsh - were all allegedly shot by Warren on March 9, 2016, at a property about five kilometres from Kawerau.

Warren was arrested following a 22-hour siege of the property.

Mauheni told the jury of seven women and four men how he and White - his armed offenders squad colleague - had been moving up a hallway in the house Warren had been hiding in, after "clearing" the kitchen, lounge, and two bedrooms.

BEVAN READ/FAIRFAX NZ Police at the Kawerau shooting roadblock at Onepu Springs Road last year.

The squad were at the home because shots had allegedly been fired at or near police during a cannabis clearance operation earlier in the day.

Mauheni said it had just occurred to him that using a police dog to investigate the remaining rooms in the house might be a safe option for the six-man clearance team, when Warren allegedly opened fire on White and himself.

"The next thing I remember is lying on my back in the hallway.

BEVAN READ/FAIRFAX NZ The siege at Onepu, near Kawerau, lasted 22 hours.

"I did not know where I was ... I knew I was in the house once I started getting dragged out.

"I could hear gunshots. I could not see."

"Do you know why you could not see?" asked Crown prosecutor Aaron Perkins QC.

"I know now that my eyes were full of blood."

Mauheni also did not know that a bullet had just struck the sighting scope of White's police rifle, shattering it. White was injured by the shrapnel while Mauheni was hit in the head by the same bullet. It split his skull bone and caused haemorrhaging and bruising to his brain.

He was rushed to Waikato Hospital, where he underwent an emergency craniotomy.

Warren is conducting his own defence in the trial and Mauheni found himself being cross-examined by the man who allegedly shot at him.

"Mr Mauheni, I hope you have recovered well from your injuries," Warren began, before grilling the policeman over the steps the squad took before "you were given the order to invade my grandmother's house."

Earlier, the court heard from Constable Martyn Roe, who spoke about the cautious entry into and through the house by a team of six officers, and the moment the first shots were fired.

They had used a "ram" to gain entry through a back door, and had then begun clearing room by room.

It was a tense process. First the kitchen and lounge at the rear were surveyed and declared safe.

Roe spoke of proceeding up a partially darkened hallway, which had doorways leading off it to the left and right.

He was in one of two bedrooms that had just been cleared while Mauheni and White were proceeding slowly up the hallway when he heard "a loud bang".

"In nanoseconds a lot was happening," Roe said.

He saw Mauheni drop to the ground, doing nothing to break his fall.

"He was just like a big kauri tree," Roe said.

Blood was all over Mauheni's face.

Roe's colleagues were shouting: "Shots fired!" "Man down!"

He heard White scream.

"It sounded like he was injured, but with a hint of fear. 'Ahh' - like if you hit your thumb on a frosty morning."

Roe fired "multiple shots" through the wall into the bedroom where the alleged gunshot had come from.

"I reacted [for the injured officers] as well as myself," Roe said.

"The intent was for [the shooter] to seek cover ... so we could gain the upper hand."

Another constable in a different room, John Ure, also opened fire through a wardrobe.

While Ure was laying down covering fire, Roe went back into the hallway and dragged Mauheni back toward the kitchen, to safety.

"I could see Constable Mauheni was exhaling pink blood out of his mouth ...I thought he was dying in front of me. I thought he was dead."

Warren also cross-examined Roe:

"Are you aware a lot of Maori are afraid of the police in the Kawerau and Te Teko area? Would you have done this to a pakeha in a flash house?" he asked.

"It does not matter where we are," Roe replied. "It just matters that the situation is dealt with appropriately."

Warren wanted to know why the police threw rocks on the roof and smashed windows of the house - which belonged to his grandmother - before they entered.

"Don't you think there could have been another approach?"

Roe said tear gas could have been used, however there was the possibility a child or an elderly person in the house as well as the person the police were seeking. It was a decision that had been made by his superiors to not use tear gas, he said.

Under cross-examination from Warren, Roe revealed he had fired 17 rounds from his M4 rifle.

"It's controlled aggression," Roe said. "You are not out of control."

Warren asked: "Is it possible friendly fire occurred? Is it possible the police shot themselves?"

"No," Roe said.

Warren asked: "Your attitude before you entered the house was I was just another low-life Maori boy?"

"That's incorrect," Roe replied.

The trial will continue on Tuesday.