Double murderer Kim Leanne Snibson broke down in the NSW Supreme Court yesterday as her accomplice Stacey Lea-Caton detailed how she killed her victims on January 28, 2006.

The pair were in court for Snibson's sentencing submissions, expected to take the rest of the week.

Snibson, 38, pleaded guilty in May to killing Nowra Hill couple Kathryn McKay and Greg Hosa at her Calymea St, Nowra Hill, house before forcing their bodies into drums and setting them alight in Tomerong State Forest.

Lea-Caton, 29, spent yesterday recounting evidence he gave during the recent trial of Andrew Wayne Flentjar, 33, of East Nowra, who was convicted of assisting in the kidnap of the couple but found not guilty of murdering them.

The families of Ms McKay and Mr Hosa yesterday heard again how their loved ones met their tragic fate.

Lea-Caton said Snibson lured the couple to the house which he was renting, first telling Mr Hosa that she wanted to talk about her horses with him.

Mr Hosa arrived at the house where he was beaten on the head with a plank of wood, tackled, hog-tied and gagged. He was dragged to the bathroom where he would have soon heard his wife's screams as she arrived only to be tackled, bound and gagged.

Although incapacitated, Mr Hosa and Ms McKay were conscious throughout the ordeal, Lea-Caton said.

Hours after they were captured, Snibson wrapped masking tape around Ms McKay's face to suffocate her before tying a noose of electrical tape around Mr Hosa's neck and putting a foot on his back while she pulled the tape up.

Snibson was crying as Lea-Caton described the killings and at times shook her head.

Lea-Caton is serving a 22-year sentence for his role in the murders and kidnappings.

He again told the court that Snibson had first asked him to help her kidnap and beat an unidentified couple, about 18 months before the murders occurred.

"She asked me to get a gun and she also asked me to tie them up and bash them," he said. It was the first time Lea-Caton mentioned a gun in his evidence.

Flentjar, who is serving a minimum of seven years' jail for kidnapping the couple, is expected to give evidence today.

Snibson's new barrister Alex Radojev cross-examined Lea-Caton, who admitted - as he had previously - that he initially lied to police and the court. However, he said he told the whole truth at Flentjar's trial and was telling the truth yesterday.