A woman obsessed with serial killers and her bondage-loving housemate have been found guilty of murdering an autistic teenager whose body was found in the backyard of their Perth home.
Jemma Victoria Lilley and Trudi Clare Lenon killed 18-year-old Aaron Pajich at their Orelia house and buried him in a shallow grave, covering it with concrete and tiles on June 13 last year.
The women blamed each other for the murder but a jury took less than three hours to find them both guilty on Wednesday after a four-and-a-half week trial in the Supreme Court of WA.
Lenon knew Mr Pajich was a friend of her 13-year-old son and she also went to the same college as him, but Lilley, 26, only met him on the day of his death.
Prosecutors said Lenon, 43, who was the first of the pair to be arrested, lured the avid computer gamer to his death.
She was the last person to phone him and told police she "accidentally" dialled his number before meeting him with Lilley at a shopping centre and driving him to the property.
Lenon said Lilley approached Mr Pajich from behind as he installed video game emulators on her computer, garrotted him until the wire broke then stabbed him three times.
Lilley denied everything, taking the stand for five days last week and claiming chilling exchanges between her and Lenon in the lead-up to the murder were research for a book she was writing.
Lilley had already written a book about a serial killer called "SOS" and adopted the character's name, while Lenon went by "Corvina", which she called herself as a submissive participant in the bondage scene.
About two months before the crime, Lenon wrote in a message to Lilley that they would be "history making".
"Profiling techniques will be re-written to accommodate SOS," Lenon wrote, admiringly describing her co-accused as a "genuine psychopath of immense control and power".
A video store manager testified Lilley had said she wanted to kill someone before age 25, and once she had fulfilled murder on her "bucket list", prosecutor James McTaggart said, she was so "full of herself and euphoric" that she couldn't help boasting about it to a work colleague.
She also left incriminating messages to her "obsequious and sycophantic" follower Lenon hours after the killing, saying she was feeling things she had "not felt before".
Their own backyard security camera captured the pair and Mr Pajich entering the house moments before the murder.
The jury was offered counselling, with Justice Stephen Hall saying the evidence had been disturbing and confronting.
The women will face a sentencing hearing on February 23.