James Hachem had become jealous of 30-year-old Samah Baker's new relationship with another man, the crown prosecutor submitted in successfully opposing his bail application.

The 34-year-old Hurstville Grove man has pleaded not guilty to murdering the NSW TAFE worker who was reported missing on January 5, 2019 and whose body has never been found.

In refusing him bail in the NSW Supreme Court on Wednesday, Justice Geoffrey Bellew said the crown case "was not demonstrably weak".

The defence had offered bail security totalling more than $2 million ahead of his June 2021 trial.

Hachem and Ms Baker had known each other for about 15 years and were said by the Crown to have been in an "intermittent intimate relationship".

The prosecutor alleged he was the last person to see her alive and the only rational explanation was that she was dead and he was responsible for her death.

According to the crown case statement, Hachem waited outside her Parramatta unit "in circumstances where he was uninvited" late on January 3 and in the early hours of January 4.

"The Crown alleged the applicant lied to Ms Baker when he advised her his parents had been involved in a car accident," the judge said.

He allegedly concocted the story in order to lure Ms Baker out of her apartment in the early hours.

He later allegedly bought various items including a double sheet, gloves, cleaning products and a digging trowel, before driving to isolated areas in rural bushland.

Prosecutor Fiona Gray said the same DNA profile as Ms Baker's was found on carpet that was formerly in the boot of Hachem's car but later found by police secreted in his wardrobe.

Justice Bellew said the Crown also alleged there was evidence of a motive, referring to text messages Hachem had sent expressing his dislike for her new relationship with another man.

In contending he may interfere with witnesses if granted bail, Ms Gray said Hachem told a friend that when police spoke to him: "It would be helpful for you to mention I was from a Christian background and it was a 'friends with benefits' situation with Samah".

His barrister Daniel McMahon said there was no direct evidence Ms Baker was dead, noting she had a history of impulsive decision-making, including attending retreats and otherwise disappearing.

She also had a troubled past and mental health issues, he said.

Referring to a purported part-jealousy motive, Mr McMahon said the couple had an on/off relationship and had maintained other relationships simultaneously with the knowledge of each other.

He referred to the long delay before Hachem faced trial and the need for him to take over minding his elderly parents, so his brother could work to fund his legal representation.

But Justice Bellew said no reason had been advanced as to why Hachem needed to be privately funded at his trial, instead of applying for legal aid.

Australian Associated Press