The 55-year-old victim was on one of her regular walks along the beach when she was grabbed from behind by Callala Bay resident Joshua Herbert on the afternoon of October 27, 2011.

The 30-year-old dragged her into the sand dunes and forced himself on her, at the same time putting his hands around the woman's neck and trying to choke her. She lost consciousness, later telling police she feared she was going to die.

When she woke, Herbert apologised for his actions, however, he then threatened to hurt her children if she told anyone.

Herbert was jailed for a maximum of 10 years when he fronted court in 2013, with Wollongong District Court judge Paul Conlon setting a non-parole period of seven years.

Herbert's lawyers challenged the decision in the Court of Criminal Appeal (CCA), arguing Judge Conlon had failed to give their client an adequate discount on his sentence as reward for handing himself into police.

The court heard that Herbert went to the police station two days after the incident and said he had seen media reports about the assault and believed he might have been involved.

He told officers he had a history of alcohol and prescription drug abuse and sometimes experienced "blackouts", during which he would fly into a rage and become violent and aggressive, then feel exhausted the following day.

He told the court he remembered filling up on booze, painkillers and crystal methamphetamine on the morning of the 27th but could not recall what had happened in the afternoon, but he felt extremely tired the next day.

He said he was having flashbacks of seeing a woman being grabbed from behind, but wasn't sure if they were dreams or memories.

Judge Conlon said Herbert's decision to hand himself in showed he was deeply sorry but he did not believe the gesture warranted a reduced sentence.

However, the CCA disagreed, saying to not give Herbert a lesser sentence would have been "contrary to the public interest of encouraging offenders to come forward".

In a decision handed down this week, the three-judge panel agreed to reduce Herbert's maximum sentence to nine years, and his non-parole period to six years and three months.