Vincent Stanford, 25, then drove home to the house he shared with his mother and collected a "rape kit" before returning to Leeton High School where Ms Scott, 26, was still working.

Unaware of what he was planning, Ms Scott then bumped into her killer and said: "I'm going home now, have a happy Easter."

But as the bubbly bride-to-be tried to open the metal gate at the school's exit, Stanford grabbed her around the waist and put his hands over her mouth to smother her screams.

He pulled her into a storeroom, which was once used as a photography darkroom, threw her on the ground and locked the door.

It was here he sexually assaulted her, then killed her by stabbing her in the neck with a knife.

Stanford told police he had punched Ms Scott unconscious, then stabbed her with a knife "to make sure she was dead".

Distressing details of Ms Scott's murder in April 2015 were revealed for the first time on Tuesday before a sitting of the NSW Supreme Court at Leeton in the state's Riverina.

An agreed statement of facts was tendered during the sentencing hearing for Vincent Stanford's identical twin brother Marcus Stanford, who had pleaded guilty to being an accessory to murder after he pawned Ms Scott's engagement and graduation rings.

Not knowing at the time what had happened to Ms Scott, her family began a desperate and agonising search as soon as she failed to return home that Easter Sunday.

The 26-year-old English and drama teacher was just days away from marrying her partner of five years Aaron Leeson-Woolley and he and her family were adamant it was not a case of cold feet.

Her sister Robyn told Fairfax Media at the time she had no idea where her sister could be.

"I spoke to her on that Saturday night, and she was over the moon, she was so excited," Robyn said.

"She had been to Griffith that day, shopping and getting ready for the honeymoon."

As the family searched and fretted, Vincent Stanford worked furiously to cover up his crime.

He placed Ms Scott's body in the boot of her red Mazda 3 and drove it to his house in Maiden Avenue, Leeton.

The car was parked behind a shed in his backyard and was left overnight until the early hours of Easter Monday.

Court documents outline how he later drove Ms Scott's car, with her naked body still inside, to Cocoparra National Park, about 70 kilometres north-east of Leeton, near Griffith.

It was a place where Stanford went on regular camping trips with his mother Annekke Noort and other brother Luke.

Just off to the side of an orange dirt road, Stanford removed Ms Scott's body from the car.

He then placed branches over her, poured petrol everywhere and set her remains on fire.

In a depraved act, he took pictures of her burnt remains, images that police later found on his camera.

When the officer in charge, Detective Sergeant Timothy Clark, later questioned Stanford about the photos, the offender told him he had downloaded the pictures "from a horror movie".

Stanford drove the Mazda back towards his home before dumping it in a field at Wamoon, eight kilometres from the Leeton township.

Witnesses later told police they saw Stanford disposing of Ms Scott's laptop in a murky canal nearby.

Bill and Gail Scanlan lived next door to Stanford and remember him waving over the fence on Easter Monday.

"We heard him come back on Monday, did all the washing, hung it all on the line, piles of it," Mrs Scanlan said.

It was not until Wednesday, April 8, that police brought Stanford in for questioning.

He initially denied having had anything to do with Ms Scott's disappearance and told investigating officers he had been grocery shopping on Easter Sunday.

But this was where he came unstuck. A sharp-thinking police officer rang the store where Stanford said he had been, and was told the business did not open on Easter Sunday.

Stanford was arrested later that night and police conducted another search during which they found Ms Scott's keys, a red bra and the boot liner of her Mazda.

A few days later, Stanford contacted police from Junee Correctional Centre and made full admissions about her abduction and murder.

The day of his confession was the day Ms Scott was supposed to be married in front of an intimate crowd at the vine-covered archway of Eugowra's Eat Your Greens function centre.

Instead of celebrating at a wedding, Ms Scott's family and Mr Leeson-Woolley gathered in a small Leeton park to pay tribute to the teacher who touched so many hearts.

Her father, Bob, told the crowd of hundreds gathered in Mountford Park that he wanted his daughter to be remembered for the great girl she was, not the tragic way she was taken away.

"Stephanie was a bubbly, bright, witty, intelligent fun-loving girl who has obviously impacted on many people here to today and our wishes for the future are that that will continue in your minds, you remember her as the girl she was … that great little girl she was."

Vincent Stanford will face a sentencing hearing in Griffith in October.