'Alcoholic blackout' suspected for ex-cop

A neurologist suspects the father of former NSW police minister Troy Grant had an "alcoholic blackout" being involved in a fatal hit-and-run crash after a Christmas party.

Dr David Rosen told the Newcastle District Court on Friday that Ken Grant's actions on the night could not be explained by transient global amnesia (TGA), a sudden temporary episode of memory loss, and there was strong evidence "this is somebody who was affected by alcohol".

Grant, 72, a retired police inspector, claims he was suffering from either TGA or sleepwalking or had sleep apnoea and was not driving voluntarily when he crashed into the victim.

Grant has pleaded not guilty in a judge-alone trial to several charges including dangerous driving causing death after running into scientist Tony Greenfield when allegedly drink driving at about 11.25pm on November 30, 2019, in the Maitland suburb of Bolwarra.

The 62-year-old scientist died of his injuries at Newcastle's John Hunter Hospital.

Grant, who had a blood alcohol level of 0.108, claimed to have no memory of the crash which threw Mr Greenfield 20m forward past his wife when they were walking to their accommodation after having been to the party.

Defence barrister Phillip Boulten SC suggested Grant could have been on auto-pilot with no conscious understanding of what he was doing or the consequences.

Mr Boulten said there had been previous sleepwalking incidents where Grant had moved irrigation pipes on a farm and gone swimming in the ocean.

Dr Rosen told the court he had viewed video footage taken by police before and after Grant's arrest and had read statements from party guests who believed Grant was intoxicated, and he did not believe TGA caused Grant's erratic driving and how unsteady he was on his feet.

"There was more going on than lack of memory," the neurologist said.

"This was not a pure memory problem."

Dr Rosen said a CT scan taken in December 2019 showed Grant had no brain abnormalities.

He said Grant's actions and loss of memory did not fit with TGA or dementia.

Questioned by prosecutor Lee Carr SC, Dr Rosen agreed Grant's lack of memory could have been caused by an alcoholic blackout.

He said an alcoholic blackout would cause the same brain disturbance as seen in TGA and usually occurred in people who were habitual drinkers.

Dr Rosen said that in the absence of any other neurological explanation for Grant's behaviour on the night, he believed an alcoholic blackout was "well within the realms of possibility".

Dr Anup Desai, a specialist sleep and respiratory physician, earlier told the court that, in his professional opinion, sleepwalkers could not drive a car or certainly not drive a significant distance without crashing.

He was sceptical Grant had been sleepwalking when he drove 850m before hitting Mr Greenfield and another four kilometres before being pulled over by police.

The first defence witness, consultant geriatrician Tuly Rosenfeld, said he was convinced Grant had been suffering from an underlying brain disease and early dementia at the time.

"I certainly wouldn't want to have his brain," Dr Rosenfeld said.

He said it was not unreasonable to suggest Grant had been sleepwalking or was in a dazed, somnolent state because of his underlying health problems, including post traumatic stress disorder, depression, chronic sleep apnoea and somnambulism.

Grant's condition would have been exacerbated by the significant amount of alcohol he had consumed and the medication he was on before the crash, the doctor claimed.

The trial will resume on Monday when Troy Grant is expected to give evidence.