Stacey Lea-Caton, 28, showed no emotion and turned to look at his family in the upper deck of the court room, as he was sentenced in the NSW Supreme Court in Wollongong yesterday.

Justice Terence Buddin said although Lea-Caton's role in the deaths of Kathryn McKay, 44, and Greg Hosa, 56, owners of a horse stud at Nowra Hill, was subsidiary his involvement had been critical.

"Two human beings have lost their lives in quite horrendous circumstances ... revealing a very considerable degree of callousness," he said.

"It is inevitable that they would have suffered a slow and painful death."

Two other people, Kim Leanne Snibson, 37, and Andrew Wayne Flentjar, 31, are yet to stand trial over the deaths.

Lea-Caton pleaded guilty earlier this month to aiding and abetting the murders and to charges of detaining the couple against their will and causing them actual bodily harm.

During sentencing submissions, he said Snibson had initiated the murders and convinced him to take part.

On January 28 last year, Mr Hosa and Ms McKay were separately lured to Lea-Caton's Calymea St home, and bound and gagged for several hours before being suffocated to death.

Mr Hosa arrived at the property about 5pm, was hit over the head with a 60cm piece of wood and wrestled to the ground.

His hands were tied to his ankles behind his back, a sock shoved into his mouth and his face taped over.

According to phone records, Snibson then rang Ms McKay, who arrived at the house soon after and was also attacked and tied up.

Ms McKay's nose and mouth were taped to stop her from breathing, while Mr Hosa was strangled with a piece of electrical wire.

After dark, their bodies were put into 44-gallon drums from a shed on their own property and transported 18km to the Tomerong State Forest, where the drums were dumped and set alight using petrol, some of which was bought by Lea-Caton. Mr Hosa's vehicle was also destroyed.

Lea-Caton gave evidence that he had not been involved in the assaults, but was left to guard the couple while Snibson and Flentjar went out to buy cleaning fluid and find the drums.

During that time, he had re-secured the rope around Mr Hosa, who had tried to break free.

He also helped clean up after the assaults and transport the bodies to the forest in the back of Snibson's station wagon.

A few hours after the murders, Lea-Caton went to Nowra Police Station, where he directly implicated Snibson and Flentjar but denied playing a part.

During sentencing submissions, Lea-Caton told the court he had wanted to tell police because "I can't live with that on my conscious". He had feared that if he did not co-operate with Snibson he too would be killed.

In sentencing, Justice Buddin said there was compelling evidence Lea-Caton had been "significantly affected" by the ordeal and that he regretted being involved.

He said Lea-Caton had had a disrupted childhood and had become depressed after the death of his best friend in a motorbike accident in which he was the driver.

Lea-Caton also suffered frontal lobe syndrome as a result of the accident and was unable to make decisions when under pressure.

He would probably spend most of his sentence in protective custody, with no access to other prisoners.

However, Justice Buddin said Lea-Caton had played a critical role in guarding the couple and was present when they were killed.

He significantly reduced Lea-Caton's sentence because of his guilty plea, although belated, his remorse and the fact he will assist police in the other trials.

Taking into account time already served, Lea-Caton will be eligible for parole on July 1, 2022.