Chilling information on the brother of Stephanie Scott's killer has been released.

Having been sentenced to 15 months in jail for his role as an accessory to his brother’s murder of the Leeton school teacher on Wednesday, a forensic psychology report claiming that the identical twin brother of Stephanie Scott‘s murderer has tried to take his own life and self-harmed on multiple occasions has been released.

According to the Sydney Morning Herald, the report by Dr Katie Seilder also suggests that prior to his arrest, 26-year-old Marcus Stanford also has a long history of drug and alcohol abuse, smoking marijuana as often as eight times a day.

Marcus Stanford. Source: Channel 7 News. 

Having been arrested and held in jail for his involvement since last year, the 15-month sentence means that Marcus Stanford will be released within the next fortnight, news that sent the Leeton community into outrage.

Launching a Change.org petition addressed to the NSW Department of Public Prosecutions following the sentence, Mark Norvall writes, "Steph was my daughter's teacher and friend - the memories of the desperate search for her are etched in my mind," continuing, "It’s a horrendous blow to us all that this man who helped Stephanie’s killer cover up her murder has only been sentenced to 15 months in prison."

Stephanie Scott with her fiancee. Source: Facebook.

Seeking to have the sentence extended, Norvall continues, "The injustice is shocking. I cannot imagine how Stephanie’s family are feeling knowing that someone who played such a key role in their daughter’s death is getting off so lightly."

The petition currently has almost 46,000 of the required 50,000 signatures.

Marcus Standford pleaded guilty to acting as an accessory to Scott's murder after it was discovered he had pawned her engagement and graduation rings for $705.

According to Dr Seidler's report, Marcus "felt sick" when he realised the jewellery his brother had sent him belonged to Ms Scott, but through loyalty did not go to the police.

Vincent Stanford being questioned by police. Source: Channel 7 News. 

"He didn't want to feel like (he'd) backstabbed Vincent," the report said.

"Mr Stanford acknowledged that he knew what he was doing was illegal but he claimed to have felt 'justified' at the time because he was 'helping out' his brother," the report continued.

Marcus' brother Vincent, who was a cleaner at the Leeton school which Scott taught, has pleaded guilty to the murder and is due to be sentenced in October.