THE mother of a Scot jailed for life for a triple murder in Australia has said she is standing by her son, calling him an easy-going, caring and happy-go-lucky boy whom she has never even seen angry.

Kilmarnock-born Jason Downie, 20, was sentenced to 35 years in prison with no parole for raping and murdering 16-year-old Chantelle Rowe and murdering her parents, Andrew and Rose, at their home near Adelaide in November 2010.

The South Australian Supreme Court heard he was sexually obsessed with the teenager and jealous of a friend dating her. He broke into her home through a window intending to kill her and her family.

Now, in a letter to the Supreme Court, Downie's mother, Lorna Carter, has said she cannot comprehend what happened or believe what her son has done.

She wrote: "Because of Jason's good nature, it's well out of character.

"At school and outside school, Jason never got into any fights or arguments with anyone and always respected the teachers."

She said he had made friends easily and got along with everyone. She added he "never swore, hit, threatened or raised his voice to myself or anyone."

Downie emigrated to Australia with his mother in 2006. He was 18 when he committed the crime in the town of Kapunda.

He admitted stabbing his three victims over 100 times but claimed he could not remember everything after entering the house. The court dismissed his claim that the killings were not premeditated.