However, Tse said Mulholland was alive for at least 35 minutes after the attack but any movements seen during the video were he described as "terminal movements, [he was] about to die".

Gabriel Yad-Elohim pictured on CCTV the day of the killing. Photo / Supplied

Yad-Elohim was arrested in central Auckland the day after the attack.

Detective Ruth Niu told the court today she first identified Yad-Elohim as police searched for the killer.

She was off-duty at the time and saw Yad-Elohim wearing a white builder's mask.

"There's absolutely no doubt it was him, I have to take action now," she remembered thinking.

But after earlier in the morning seeing the footage of the attack she had concerns about her safety and the public's.

She followed Yad-Elohim.

"I had no radio, no taser, I had nothing to protect myself," she said.

She phoned Detective Ray Fa'ofo and as he arrived, Niu tapped Yad-Elohim on the shoulder.

"Excuse me, can I have a word?

"He looked at me and said 'no'."

Fa'ofo then made the arrest with Niu helping to restrain Yad-Elohim as he struggled a little bit.

"It wasn't my fault, it's all covered, it wasn't like that you'll see," Niu recalled Yad-Elohim telling the detectives.

"He just seemed quite defensive," she said.

Later in the police car as the detectives transported the murder-accused to the station, Yad-Elohim said, "I'm trained in self-defence".

Niu, who was driving, recalled thinking it was an odd thing to say.

Yesterday, Lummis described the killing as a "drug deal gone wrong".

She said it was Yad-Elohim's desire to obtain drugs which led to "the fatal events of that evening".

Yad-Elohim, who has been remanded to the care of the Mason Clinic since he was charged, suffers from "treatment resistant" schizophrenia, the court has heard.

He has suffered from mental health issues during the past 10 years.

However, Lummis said, Yad-Elohim's drug use led to the killing and he was well enough to be released from medical care.

The trial continues.