They drugged, bludgeoned and strangled their 16-year-old victim to death then they knelt over her lifeless, bloody body to kiss before dumping her in a wheelbarrow.
The horrific murder of Stacey Mitchell has attracted national headlines in Australia but questions remain as to why her roommates of only four days, Valerie Page Parashumti and Jessica Ellen Stasinowsky, violently attacked and killed the former Leeming High schoolgirl.
Supreme Court justice Peter Blaxell sentenced Parashumti, 19, and Stasinowsky, 21, to 24 years in jail each.
Blaxell said the "particularly horrifying and shocking" crime was devoid of a substantial motive.
"You have each had more than a year in custody to reflect upon the evilness of your crime yet you still lack remorse and obviously place no value on the sanctity of human life," he said. "There is also the added problem that you each enjoy being sexually aroused by the infliction of violence."
Stasinowsky and Parashumti, who had been together just a month, have offered no explanation or motive for the killing other than that Stacey "annoyed'' them.
One theory put to the court was that the couple appeared obsessed with proving their love for each other.
Both pleaded guilty last November to one count each of willful murder but they still do not seem to understand the gravity of their crime.
Court hearings have been punctuated with laughter, smirking and smiling.
Even during sentencing submissions in January, the couple was told twice by Blaxell to stop their light-hearted behavior as the graphic details of the crime were read.
Stacey was killed in the early hours of Dec. 18, 2006, at the Lathlain house she shared with Parashumti and Stasinowsky after running away from home 11 days earlier.
She moved in during the evening on Dec. 14, but told her parents the day before she was killed that she wanted to return home.
Police found her body four days later, upside down, in a wheelbarrow in a shed at the back of the house.
Prosecutor Dave Dempster described the killing as a sustained attack that lasted at least half an hour. He has demanded strict-security imprisonment — a non-parole period of at least 20 to 30 years.
"It appears that the deceased was killed simply because she was found to be annoying to the offenders,'' Dempster said.
A fourth housemate, David Ross John Haynes, 27, has been jailed for two years for being an accessory after the fact to the murder, which took place at his father's house.
The court heard the attack started in the kitchen after the trio had been drinking alcohol and Stacey had been slipped a sleeping pill.
Dempster said Parashumti started raining blows on Stacey while Bach's "St John's Passion" was playing throughout the house.
During the attack Parashumti complained Stacey was taking too long to die so she continued to beat her while Stasinowsky wrapped a belt chain around her neck.
The women monitored her pulse after she fell unconscious and then kissed each other over the body once she died.
Then they videotaped the blood-drenched crime scene on a mobile phone, on which they are heard mocking Stacey's English accent.
"It ends with Parashumti saying, 'I tell you man, when I was beating the f--- out of her with a rock,' and then there's laughter from Stasinowsky,'' Dempster told the court.
Neither of the two killers had serious criminal records and both were young women — Parashumti was 18 and Stasinowsky was 19 at the time of the murder.
Parashumti's lawyer, David Edwardson, said his client had never had a serious relationship before meeting Stasinowsky.
Edwardson said Parashumti had a violent family life and had also been associated with the vampire subculture since the age of 10 when she started experimenting with drinking blood. At first from her own cuts then later that of others.
He said initially Parashumti liked Stacey but the friendship quickly became strained when Stacey talked about committing suicide.
"Anyone who kills themselves obviously they don't appreciate their own lives [sic]," the court heard Parashumti told her lawyer. "I wish I had a f---ing perfect world.''
Stasinowsky too had a troubled adolescence before leaving home at 16.
As an only child of a single working mother, the court heard she felt extreme loneliness and was "emotionally barren."
Stasinowsky's lawyer Andree Horrigan said her client believed the relationship with Parashumti was "strong and solid."
"There was always this basis that she and Ms Parashumti were a unit and were conjoined essentially,'' she said. "They were a partnership.''
By all accounts, Stacey was a typical teen — outgoing, fun-loving and full of youthful spirit.
Her MySpace Web site was decorated with bright pink wallpaper of Playboy bunnies.
"My name is stacey, Im english, I love me alochol, i'm a party gurl, music is me life, i cant live with out my friends, im a very loud person, i talk 24/7, im a very down to earth person if you get to know me ...xxx,[sic]'' the Web site said.
Stasinowsky and Parashumti's lawyers have both asked the judge to consider their young ages and early guilty pleas in sentencing.