WARNING: DISTRESSING CONTENT

A mechanical engineer who visited the Remuera home of eye surgeon Philip Polkinghorne gave a step-by-step description today of how the eye surgeon’s wife might have died by suicide.

Prosecutors, however, remained sceptical, suggesting to jurors at Polkinghorne’s ongoing murder trial that there were so many unknown variables that the expert’s calculation was basically meaningless. His testimony also missed the point, Crown solicitor Alysha McClintock suggested.

“Do you understand ... the theoretical possibility of this is not an issue?” she asked.

Polkinghorne, 71, is accused of having fatally strangled Pauline Hanna, 63, before staging the scene inside the foyer of their home on April 5, 2021, to look like a suicide by hanging. Prosecutors have suggested the surgeon had a significant methamphetamine habit and might have been under the influence of the drug when he attacked his wife during an argument - possibly over his lavish spending on sex workers or a secretly blossoming relationship with Sydney escort Madison Ashton.

Polkinghorne’s lawyers, now in their third day of calling evidence after five weeks of Crown testimony in the High Court at Auckland, have argued that police were too distracted by salacious details of the couple’s personal life to see the obvious: that it was indeed a suicide by someone suffering long-term depression and immense work stress.

Engineer Andrew McGregor, who runs an Auckland company specialising in the investigation of engineering failures and accidents, was called this afternoon to give credence to the defence contention.

Most details of McGregor’s testimony have been suppressed by Justice Graham Lang to reduce the risk of suicide contagion - when details about self-harm prompt vulnerable people to hurt themselves. The Herald has, for similar reasons, voluntarily refrained from publishing non-essential details regarding the possible mode of death during previous witnesses’ evidence.

But McGregor’s broad conclusion can be published: that it was physically possible for Hanna to have died via hanging in the manner described by Polkinghorne to police in the immediate aftermath of his wife’s death.

The engineer conducted his tests at the Remuera home on June 30 and July 9 this year. The defendant was home but not observing the simulation, he said.

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During cross-examination, McClintock said the real matter of contention was whether Hanna could have committed suicide with a rope as loosely tied to the upstairs balustrade as noticed by police. McGregor said he did not take that factor into consideration when conducting his tests because there was not enough information about how the rope had been tied.

McGregor agreed with McClintock that, while understanding angles and weights due to his background as an engineer, he does not have a pathology qualification. He also agreed that he needed to do some medical research on the suicide method ahead of the simulation.

“Were you aware if Pauline Hanna had any engineering qualifications?” McClintock asked, adding: “Were you aware if Pauline Hanna did any research like you did?”

“No, I’m not aware of that history,” he responded.

Jurors had earlier reviewed internet searches recovered from Hanna’s phone and laptop. None appeared directly related to suicide.

But McGregor said he doubted an engineering degree or research was necessary.

The engineer’s testimony followed two earlier witnesses today - Hanna’s hairdresser, who described how she was often distracted by work during her appointments, and an accountant who took jurors on another deep dive into the couple’s finances.

McGregor’s testimony was briefly interrupted just before the afternoon break with a farewell from former Crown solicitor Brian Dickey, who has served as co-counsel up until now alongside current Crown solicitor McClintock. Dickey told the jury he had a longstanding personal commitment, which had been known before the trial began, and wouldn’t be returning to court for the duration of the trial.

“It’s not a surprise to me,” Justice Lang confirmed to the jury.

The defence is set to continue calling witnesses tomorrow morning.

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Craig Kapitan is an Auckland-based journalist covering courts and justice. He joined the Herald in 2021 and has reported on courts since 2002 in three newsrooms in the US and New Zealand.

The Herald will be covering the case in a daily podcast, Accused: The Polkinghorne Trial. You can follow the podcast at iHeartRadio, Apple Podcasts, Spotify, through The Front Page feed, or wherever you get your podcasts