Ken Grant on trial for alleged fatal hit-run near Maitland in 2019, which killed Tony Greenfield

A court has heard Ken Grant, the father of ex-police minister Troy Grant, exhibited “absentmindedness’’ and ‘’deterioration’’ in the years leading up to an alleged hit-and-run.

A court has heard in the five years leading to the arrest of Ken Grant for an alleged fatal hit-and-run in the Hunter Valley in 2019, his health saw significant decline, gaining weight, dressing disorderly and he had exhibited “absentmindedness’’ and “deterioration’’ in his decision making ability.

Troy Grant, the former NSW Police Minister and son of Mr Grant snr, gave evidence in his father’s trial via video link at Newcastle District Court on Monday.

The 72-year-old former police officer is accused of being drunk behind the wheel when he ran down Sydney scientist Tony Greenfield in his Mazda ute as they left a Christmas party at Bolwarra, just outside of Maitland, on November 30.

Kenneth Grant (left) and ex-police minister Troy Grant (right).

Troy Grant said his father would have random incidents of “forgetfulness’’ and would leave the house unlocked and open on regular occasions, where police would call him to check on his father’s welfare.

He told the court his father’s sleep walking was a frequent part of the family discussion.

“It’s been a common subject matter in our family, couple of notable incidents,’’ Mr Grant jnr said.

On one occasion he recalled his father trying to climb out the bedroom window in the middle of the night after he said he was going for a swim, when he was around 14 living with his family in Kootingal.

His mother had to stop him and return him to bed.

“His eyes were open, upright but he didn’t look like he was with it,” Mr Grant jnr said.

Troy and Ken Grant (middle) leaving court. Troy Grant told court his father suffered sleep walking and his health was in decline in five years before alleged hit-and-run. Picture: Dylan Robinson

Again 12 months later he told of how his father had walked out into the garden and moved the sprinklers and tried to get back into bed dirty and wet, while he was also told about an occasion where his father had moved irrigation pipes on the farm while sleep walking.

The court heard sleep walking was a Grant family trait.

“I was caught in embarrassing situations,’’ he said.

The court heard that as a 17-year-old, Mr Grant jnr woke up in a stranger’s house while staying at a holiday home with friends, and on another occasion wore a bedspread like a cape and handed his mother a miniature cricket bat while she was in the middle of a tupperware party with friends.

“I was nicknamed godilocks. Sleep walking wasn’t unusual in the family, we didn’t think too much of it,’’ Troy Grant said.

Mr Grant snr has pleaded not guilty to dangerous driving occasioning death; failing to stop and assist; police pursuit and mid-range drink driving.

Where Mr Greenfield was hit and killed following a hit and run on Flat Rd, Bolwarra on NOvmebr 30, 2019. Google street view

The defence case is based on that he suffered from sleep apnoea, and transient global amnesia (TGA), a temporary memory loss condition, and was sleep walking on the night of the crash.

Defence barrister Phillip Boulten told the court because he was ‘’not acting voluntary’’ behind the wheel, he couldn’t be made responsible.

Through the trial last week some medical experts concluded Mr Grant snr had suffered an ‘’alcohol blackout’’ and that would explain the behaviour and lack of memory on the night of the fatal crash, and that driving impairment with TGA, with a combined low dose of prescription drugs, was ‘’highly improbable’’.

An expert medical witness in the trial of Ken Grant concluded he suffered an ‘alcohol blackout’. (AAP Image/Darren Pateman)

The court heard that a number of witnesses at the party had observed Mr Grant snr “hammered’’ and “well and truly gone’’ after he had consumed beer and red wine that night before leaving at around 11.30pm.

Mr Greenfield and his wife were walking along Flat Rd in a bicycle lane to their accommodation after the party when the court heard he was hit by a vehicle from behind, propelling him 20 metres forward.

Triple-0 was called and he was taken to John Hunter Hospital but early the next day passed away from his injuries.

The court heard Mr Grant Snr failed to stop after the collision and was observed to be swerving all over the road, before he mounted a median strip and eventually stopped following a low-speed pursuit with police.

The 72-year-old announced his son was the ex-police minister before saying “I am pissed”, with a breath test indicating he was more than twice the limit.

The court heard during an interview with police he said he had no memory of the collision, but that DNA swabs of his vehicle found it matched that of Mr Greenfield.

Closing submissions in the trial are expected to be heard on November 22.