Cassie testified today that there was no sexual relationship with either man.

Fanning was stabbed six times to his chest and neck, and Matthews was stabbed 15 times. His throat was cut.

Cassie will testify that she heard calls for help coming from the rear of the shop, Marchant said.

She then, "to her horror", saw Tarapata walking towards her, he said.

"He looked wild, he looked possessed, he had blood on his hands and he was also carrying a knife in his left hand," Marchant said.

Cassie said Tarapata was clutching a 10-15cm silver knife and "didn't look normal".

"I described him looking possessed ... Everything, his actions, his moving, he was breathing heavily, it didn't look like him at all," she told the court.

"His eyes were like really red."

More cries for help could be heard coming from Matthews, the court heard, before Tarapata made his way back towards where the voice was coming from.

Marchant said it was likely to "finish him off".

Tarapata and Cassie then returned to their car and drove around West Auckland, while Tarapata read his Bible.

He washed his bloody hands when the couple stopped near the Avondale Racecourse, the court heard.

One of the knives used in the killings was also buried in a garden and found by police, Marchant said.

Tarapata was arrested later that day in Huntly, where he said his parents lived.

The killings may seem like "it's crazy, it's unhinged, it's madness", Marchant said, "but there is a big difference to what you and I may think is insane and what the law defines as being insane".

"The test for insanity requires much more than someone being delusional, much more than someone hallucinating, much more than someone being paranoid or suffering from schizophrenia. This defendant was suffering from all of these.

"He knew what he was doing, he intended to kill them, and he understood that when he was doing these things it was morally wrong."