A defence expert medical witness says there is “no doubt” a man accused of murder was suffering from an acute distress disorder resulting from past trauma.

That was the evidence of psychiatrist Dr Craig Immelman, who examined the Bay of Plenty man accused of murdering Jamin Roemaata Harrison at a McLaren Falls Rd, Ōmanawa property on January 25, 2021.

The defendant, whose name is suppressed, is on trial in the High Court at Rotorua defending a charge of murder, having shot Harrison dead in the driveway of the property.

Harrison, 30, died from a shotgun injury with significant injuries to his liver, spleen, aorta and left common iliac artery, resulting in significant internal bleeding, the jury was told.

The defendant does not deny shooting Harrison with a 12-gauge break-open double-barrelled shotgun, but told police and ambulance staff he thought Harrison and his associate had come to “shoot him”.

The defendant also told police he thought Harrison had a gun and was aiming at the car, and was defending himself and his partner after previously being assaulted and seriously injured during a home invasion.

The Crown says Harrison was unarmed when he turned up at the property to buy drugs, accompanied by his cousin Janelle Nicholas, who was driving her mother’s car about 10pm.

A CCTV camera captured Harrison standing at the front gate of the property, before he was then shot after less than a minute.

During his opening statement to the jury yesterday, defence lawyer Phil Hamlin said the defendant elected not to give evidence but would call three witnesses - a local farmer, a GP and the psychiatrist.

Psychiatrist Dr Craig Immelman would give evidence of the impacts of having an acute distress disorder from a past trauma, which “heightened a victim’s sensitivity and reaction to a real or a perceived threat”.

Hamlin said despite calling these witnesses, the responsibility for proving the defendant guilty still rested with the Crown and the defendant did not have to prove his innocence.

The defence’s case is that the defendant acted in self-defence to protect himself, his partner and another person at the address, fearing for their safety after unknown visitors turned up at the property.

Immelman said he interviewed the defendant, listened to 111 calls made by him and his partner, reviewed medical records, witness statements and a video-taped reconstruction of the events leading to the shooting.

He also reviewed a psychologist’s report about the results of “psycho-metric” testing of the defendant undertaken in August last year, he said.

Immelman said the psychologist concluded that the results of this testing were “entirely consistent” with a diagnosis of post-traumatic stress disorder which had begun with acute distress disorder symptoms.

He said he agreed with that conclusion.

Some of the characteristics of acute distress disorder would lead to a person becoming “hyper-aroused and anxious and in some cases detached from reality and not having the usual reactions to similar stressful situations”.

“My examination and the material available to me clearly points to the defendant not thinking as he would if the injuries had not occurred. "

Immelman said while he was not able to say with certainty that the defendant had suffered a concussion from the earlier assault, he “suspected” it was part of the impacts of that trauma.

“In terms of a diagnosis of an acute distress disorder, in my view, there would be no doubt that is correct because at present, the defendant clearly has a post-traumatic stress disorder.”

Immelman said a striking characteristic of the acute distress disorder people experience after a traumatic event is a “sense of detachment and kind of glazed-over feeling”.

“And a feeling of unreality and difficulty remembering details of events ... and it’s a protection mechanism and helps us [in] managing overwhelming anxiety and stress.”

Immelman said the disorder could easily lead the person to misinterpret events and perceive an imagined threat as real.

“I have no doubt that the defendant was suffering from an acute distress disorder at the time of [the] shooting.”

Under cross-examination by Crown prosecutor Richard Marchant, Immelman conceded his interview with the defendant was more than two years after the shooting.

Dr Jack Drummond, who has a Master’s degree in forensic medicine, confirmed he reviewed formal statements of the defendant and his partner, medical records and photos of the defendant’s injuries relating to the previous home invasion.

Drummond said it had taken considerable force to cause most of the defendant’s injuries, which included a head injury, but noted the emergency department doctor stated the defendant had a stable neurological condition (meaning he wasn’t neurologically impaired).

He said there is no doubt the assault would have been a “fairly traumatic situation” for the defendant.

A local farmer gave evidence about seeing two cars parked down the road about 60 metres apart from where the shooting took place about 10pm on January 25, 2021.

“Then I saw another car heading back towards State Highway 29 which suddenly dipped its lights, which made think they knew each other, and then the two cars slowly turned around and followed the third car.

“... I’m not a suspicious person but what they were doing didn’t look right.”

The trial presided over by Justice Grant Powell continues.