Stephanie Scott's mum says she has nightmares about her daughter's final moments.

“Pathetic”. “Inept”. “Despicable.” These are the words used by the mother of murdered NSW school teacher Stephanie Scott to describe Vincent Stanford – the opportunistic cleaner who brutally slayed the 26-year-old just days before her wedding.

Merrilyn Scott delivered a powerful victim impact statement as part of Stanford’s sentencing hearing at Griffith Supreme Court this morning, during which she admitted to suffering nightmares about her daughter’s final moments.

“Nights are haunted by visions so terrible it is difficult to find rest,” she said.

“Did she see the knife? Did she see the fist before he pounded her precious life into oblivion?”, Merrilyn Scott said, according to The Sydney Morning Herald.

She went on describe Stanford as “pathetic”, a man who lead an “inept life” and had no right to take Stephanie’s life.

“He should not have been there, but such is his arrogance he did as he pleased,” she said, according to news.com.au.

Scott’s family arrived at court wearing yellow – the slain teacher’s favourite colour, and one that became a staple of the floral tributes laid throughout her hometown of Leeton.

Stephanie Scott and her mother, Merrilyn, at her bachelorette party. Image: Facebook.

The 25-year-old school cleaner pleaded guilty to the aggravated sexual assault and murder of Scott, whom he killed on Easter Sunday, 2015.

The teacher was working overtime preparing lessons for a substitute, when Stanford set upon her in the Leeton High School staffroom, raped her, punched her and later stabbed her in the neck.

After an intensive police search, Scott's badly burnt body was eventually found 70km away at Cocoparra National Park on April 10, 2015 - just days before she was due to be married to partner Aaron Leeson-Woolley.

Police later discovered that Stanford had taken depraved photographs of her charred remains.

The court this morning heard a recording of Stanford's police interview, during  told police he "went a little nuts" when he killed Scott, reports The Sydney Morning Herald.

"I don't know, I just felt like I should do it," he told investigators. "Just that I had to kill her."

"I think I needed to see a psychiatrist but I didn't."

The court was also told Stanford confessed to attempting to strangle a teacher when he was 13-years-old and living in The Netherlands - an attack that saw him committed to a mental institution for two months, reports The Sydney Morning Herald.

Stanford's identical twin, Marcus, walked free from prison in September, having served a 15-month sentence for being an accessory to Scott's murder.

The 25-year-old had admitted to selling two of Scott's rings, which his brother had posted to him along with Scott's drivers license.

Merrilyn Scott also spoke ahead of Marcus' sentencing, and said there would "be no end to the sorrow" she and her husband, Robert, felt over the loss of their little girl.

"Even as we searched, Stephanie's fate was known by a second person. Both were part of something so monstrous, so cruel and heartless, devoid of any of the qualities that make us moral human beings," Mrs Scott told the court, according to The Sydney Morning Herald.

"These treasured little rings that had meant so much had become trophies. The vision of them being removed from Stephanie's gentle, loving hands sickens us and fills us with despair."