A JUDGE in Australia has condemned the "cold-blooded, merciless" killings carried out by a Scots teenager who raped and stabbed a pregnant 16-year-old and her parents, as he sentenced the 19-year-old to 35 years in prison.

Justice John Sulan said that Jason Downie, a car mechanic who moved to Kapunda, near Adelaide, six years ago, had committed a "chilling" string of murders on November 8, 2010.

Downie, originally from Onthank, Kilmarnock, had broken into the home of Andrew and Rose Rowe and their daughter, Chantelle, because he was "sexually obsessed" with the girl and jealous of his friend who was dating her, the Supreme Court in Adelaide heard.

Downie admitted to the murders and was sentenced to life yesterday.

Justice Sulan said Downie had stabbed Mr Rowe 10 to 15 times with a kitchen knife after he became aware of an intruder in the house, before turning on Mrs Rowe. "You killed [her] simply because she witnessed your attack on her husband," said Justice Rowe.

After stabbing Mrs Rowe 50 times, Downie followed their 16-year-old daughter Chantelle into her bedroom where she hid under the bed.

"You stabbed her two or three times, pulled her out from under the bed ... she must have been terrified by what she had seen," said Justice Sulan.

Believing that Chantelle, who was pregnant, was dead, Downie undressed her. When she began to regain consciousness he ran to the kitchen to grab another knife and resumed stabbing her. When she "became weak", Justice Sulan said, Downie raped her.

The horrific account sparked fury in the courtroom, with Chantelle's family members yelling "you will die" and "they are going to have you" at Downie. Two women ran from the court in tears, while a third had to use an asthma puffer.

Justice Sulan called for calm before proceeding to sentencing. He rejected Downie's claims he had gone to the Rowe house to confront Chantelle's boyfriend.

He said: "I am satisfied beyond reasonable doubt that it was your intention to make sexual advances toward Chantelle Rowe and to have sexual intercourse with her. I am satisfied you held an attraction toward her [but] any relationship other than that of a friend was a figment of your desire and imagination, rather than fact."

He said Downie's personal history did not exhibit "any of the criminological characteristics" of typical defendants.

Justice Sulan added: "The murders of three innocent victims must carry with it a severe sentence. I do not accept that your conduct was of someone who was not thinking rationally.

"The cold-blooded, merciless attack on Chantelle, who had hidden under the bed in fear, was a chilling act."

Justice Sulan said Downie's non-parole period would have been 42 years, if not for his guilty pleas and prospects of rehabilitation.

Outside court, Mr and Mrs Rowe's son, Christopher – the only surviving member of the family – was too distraught to speak. His cousin, Kylie Duffield, read a statement on his behalf.

It said: "While many feel my family and I have reached some form of justice today, I find it hard to agree.

"The lives of my dad, mum and sister viciously taken by someone of sound mind qualified this bastard, Jason Downie, to 35 years non-parole, while my family and I continue to serve life. Please explain to me the 'justice' in this."