Lawyers for Illawarra man Colin Maxwell Farrow successfully applied to the court earlier this month to have a judge alone determine the fate of their client, who is alleged to have brutally murdered mother Linda Jane Stevens in a drug deal gone bad.

In most serious criminal cases, a jury determines the guilt or innocence of an accused person.

However, Justice Stephen Rotham agreed to the alternative course, which was opposed by the Crown, saying he feared the exceptionally limited availability of one of the key witnesses may inadvertently sway the jury.

He said in the situation where the determination of the case would come down to which expert psychologist was more believable, he worried jurors might be swayed by the absence of one of the them.

"There is a real danger that the jury will determine the matter not on the basis of the expert evidence, but on the basis of the ability of one or other of the experts to give evidence that is more compelling or convincing in an irrelevant sense," Justice Rotham said. "My preference, in criminal trials, is for guilt to be determined by a jury and not by a judge sitting alone.

"Nevertheless, in the circumstances of these proceedings ... I am satisfied that it is in the interests of justice that the matter be heard by judge alone."

The court heard Farrow would not contest the fact that Ms Stevens' death was his doing but will argue he had a significant mental illness at the time, and therefore cannot be held criminally responsible for his actions.

Police found Linda Stevens' body, with multiple puncture wounds, in the boot of a car at Corrimal in April 2013 after receiving reports from motorists about erratic driving.

Ms Steven was found naked with a pair of boxer shorts over her head and her body wrapped in bed linen. Her hands had been tied behind her back and her mouth gagged with gaffer tape.

"The victim had multiple stab wounds, predominantly around the chest and neck area," Justice Rotham said in recounting the basic facts of the case.

"Police identified the victim by use of fingerprints and, on examination of the interior of the vehicle located a mobile phone that was later identified as belonging to [Farrow].

"Police also discovered a pick and shovel on the back seat of the vehicle and a number of bags containing various items. [Farrow] purchased the pick and shovel from Bunnings Warehouse in Wollongong earlier that day."

Justice Rotham said Farrow had apparently gone to Ms Stevens' house that day to buy drugs.

Police who searched Farrow's house a few days after the arrest discovered a handwritten note containing details of what police suggested were three different people, one of which was Ms Stevens, with notations suggesting the advantages and disadvantages of harming each or all of them.

There was also a handwritten list of items, including mask, gaffer tape, gloves, pliers, garbage bags, hacksaw and blades, spades/entrenching tool and ammonia.

The list finished off with the words "Be THOROUGH, Be METHODICAL and most of all, BE CAREFUL".

The trial is set to begin in early February in Sydney.