Kenneth Wayne Grant, now 72, a retired police officer, claims he was sleepwalking and was not driving voluntarily when he hit and killed scientist Tony Greenfield at Bolwarra in November 2019.

Grant has pleaded not guilty to dangerous driving occasioning death, failing to stop and assist after impact causing death and police pursuit and is facing a judge-alone trial in Newcastle District Court.

During his closing address on Monday, Crown prosecutor Lee Carr, SC, pointed Judge John Hatzistergos to the evidence of an expert who said it would have been an "extremely unusual occurrence" for Mr Grant to be sleepwalking at his age.

"There is just no evidence of sleep apart from this observation of "nodding off"," Mr Carr said, referring to a statement from someone at the Christmas party.

"Which is then elevated to the status of sleep and remains continuous for a period of time, long enough for [deep sleep] to commence and then go into this somnambulistic state. "And that is against a background of nothing of any such nature being reported for more than a decade and it being an extremely rare event to occur in somebody of that particular age."

Defence barrister Phillip Boulten, SC, said Mr Grant had a history of sleepwalking and it was a reasonable possibility that he was in a somnambulistic state at the time his vehicle struck Mr Greenfield as he walked home from the party.

Judge Hatzistergos will deliver verdicts at a later date.