Roger Phillip McGrath, 55, faced Wagga District Court for sentencing on Thursday after he pleaded guilty to taking and detaining the 76-year-old to commit a serious indictable offence, occasioning actual bodily harm.

On February 2, McGrath's mother told him that she and her husband would be going on a holiday, and he would have to find somewhere to live while they were away.

According to court documents, this enraged McGrath, who broke a window and damaged some items.

The woman sought refuge and called police, but McGrath later returned, shouting aggressively at her.

He took her phone off her and threw it away before pushing her into his vehicle, knocking over her walker. When she tried to escape, she was hit on the head.

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McGrath drove away from the house, saying he would kill her before driving up Talbingo mountain on the Snowy Mountains Highway.

After his car stalled and stopped, the mother was dragged across the highway and pushed over the guard rail down the embankment.

However, some shrubbery stopped her fall, and McGrath fled on foot as a witness returned to help.

Emergency services performed a vertical rescue, and she sustained bruising to her body and "deep skin tears" to her arms and legs.

On February 4, police found McGrath lying under a bed. He told police he couldn't remember most of what happened.

In court, defence barrister Robert Hussey provided written submissions and a forensic psychological report.

He told the court McGrath re-entered the community in 2016 after nine years in jail and had since demonstrated an aptitude for rehabilitation, most notably by gaining employment.

Mr Hussey said there was also a "steady build-up of grievances" between McGrath and his mother, and he was dealing with the loss of a friend.

Mr Hussey said while this was no excuse, it provided context to what happened.

He said McGrath knew he had "effectively destroyed his relationship with his mother, and that is something that brings him great sadness".

Mr Hussey said the offence was "unplanned" and fell below the mid-range of seriousness.

McGrath had also suffered "deprivation and disadvantage" in his upbringing, Mr Hussey said, and he had poor emotional self-regulation capacity.

"He is someone who is capable of rehabilitation because he has already done it," he said.

"He needs to do a lot of work on himself, he acknowledges it ... he is someone who can comply with a law-abiding lifestyle ... he was in the community for three-plus years offending free."

Crown prosecutor Lisa Hanshaw argued a finding could not be made that the offender was remorseful and he had suffered circumstances of childhood deprivation and disadvantage.

She said these were untested claims made in the psychological report, and his mother had made a reasonable request for him to live elsewhere why she was away.

"That is not a grievance that could in any way, shape or form justify how the offender acted towards his mother," Ms Hanshaw said.

Mr Hussey said McGrath had expressed remorse and the prosecution did not oppose the report's submission.

Judge Jon Williams said McGrath had a criminal record dating back to 1983, which included a charge of common assault against his mother in 1987.

Judge Williams noted the psychologist deemed him a "moderate risk" of future violence, and his case needed special management strategies to help him address past trauma and rehabilitate.

He referenced the victim impact statement in which the mother described having "flashbacks".

"Her biggest fear is feeling unsafe once he is released from custody ... what occurred to her albeit over a short period of time must have been extraordinarily frightening," he said.

McGrath was jailed for three-and-a-half years after a finding of special circumstances was made.

He is due for parole in February 2023.

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