Dee Annear thought she was going camping with the man she loved. Hours later, she was dead.

A man will spend more than 20 years in prison for killing his partner in a remote forest in an "inexplicable" attack.

Rohen James Hanson was camping with his partner Dee Annear in the Bulga State Forest on the NSW mid-north coast when he murdered her in September 2021.

"This is a tragic case involving the brutal and unexplained killing of an innocent woman," Justice Ian Harrison said on Friday.

Justice Harrison rejected each of Hanson's multiple explanations for why he killed Dee, including that it was in self-defence after she swung a glass bottle at him.

"Brutal and cruel and inexplicable", the judge labelled the killing.

But he stopped short of saying the 42-year-old planned the attack or intended to kill her from the outset.

The attack was a "loss of self-control that may have been fomenting for some time," Justice Harrison said.

Hanson disposed of a bloodied mattress and cleaned up the blood in the remote logger's hut where the murder took place, he found.

The killer also initially lied to police about how Dee died, saying she sustained her injuries when he crashed his ute driving to the hut.

"It's all the truth, that's what happened," Hanson said when questioned about whether the car crash account was true.

Dee's body was found outside a remote logger's cabin in 2021. Image: Facebook/deeannear.

In later police interviews, Hanson claimed he tackled Dee against a wall in self-defence when she hit her head and only disposed of the mattress because "it looked like I f***ing murdered her".

But there was no evidence Hanson was acting in self-defence while attacking Dee over the course of at least 25 minutes, potentially several hours, the judge found.

"I reject that Ms Annear was an aggressor," he said.

Several witnesses testified in the trial about the violent nature of Hanson's relationship with Dee in the roughly four years they were together before the murder.

Hanson had a long history of domestic violence and substance abuse.

He pleaded guilty to manslaughter but not guilty to murder at the start of his Supreme Court jury trial.

The jury found him guilty of murder in July.

In a letter to the court, Hanson expressed remorse for his actions, saying his actions were "shameful, despicable and disgusting".

Justice Harrison ordered him to serve 28 years in prison with a minimum of 21 years.

Hanson will be eligible for parole in September 2042.

Featured image: Facebook/deeannear.