Jemma Lilley and Trudi Lenon murdered Aaron Pajich 'for pleasure'

Aaron Pajich was murdered by Jemma Lilley and Trudi Lenon in 2016

Warning: This article contains details that readers may find disturbing

Inside a nondescript brown brick house in suburban Australia, Jemma Lilley and her housemate Trudi Lenon hatched a plot to make history as serial killers.

Their first and only victim was Aaron Pajich, 18, a slightly-built and trusting computer game enthusiast with Asperger's syndrome who thought he was among friends when he was murdered inside the women's Perth house on 13 June, 2016.

In November last year, Lilley, 26, a British immigrant, and Lenon, 44, were found guilty of Mr Pajich's murder, despite Lilley's belief that police weren't smart enough to catch her.

On Wednesday, the Supreme Court of Western Australia gave the pair a maximum sentence of life in prison with a non-parole period of 28 years.

"You killed for your own pleasure," said Justice Stephen Hall in sentencing.

How the plot began

Lilley arrived in Perth from Stamford, Lincolnshire, in 2010. She had a troubled childhood and developed what prosecutors later said was a long-term fascination with the horror genre, murder and serial killers.

Jemma Lilley enters a shopping centre on the morning of the murder

They say she regarded Freddy Krueger, the serial killer protagonist in the A Nightmare on Elm Street film franchise, as a hero and allegedly once told a friend that she wanted to take a life before she turned 25.

In 2012, with her visa almost expired, she married a gay friend who later died. His best friend introduced her to a friend of his, Lenon, in 2016. The pair became close very quickly.

At that time, Lilley was working as a shelf-stacker at a supermarket. She had also published an online novel that had a serial killer theme and a central character known as SOS.

Lenon, a mother of two boys, had been engaged and was a "submissive" in Perth's bondage, discipline, sadism and masochism (BDSM) community.

She went by the name Corvina in the BDSM scene, and bore a tattoo from that relationship that was effectively a brand of ownership.

Lenon struggled financially after her engagement ended. When Lilley visited Lenon's home in May 2016 and saw its parlous state, she offered to move Lenon and her boys into her home. Lenon agreed.

The women were already sharing homicidal fantasies in conversations and in online messages, police say, building a dominant-submissive friendship, with Lenon doting obediently on Lilley.

Security footage captured Lenon (top, with trolley) and Lilley (below centre, in black) shopping a day before the murder

They used the codenames SOS and Corvina. Prosecutors say their exchanges intensified rapidly until, within three weeks of living together, their bizarre plan reached fruition.

Thirteen days before the murder, each declared themselves ready to kill.

In an online exchange, prosecutors allege Lilley wrote: "I feel as though I cannot rest until the blood or flesh of a screaming victim is gushing out and pooling on the floor... I cannot shift this belief that the world has become not only ready for me but it needs me to be ready."

Lenon allegedly replied: "It is definitely time - I am ready, you are ready".

Vulnerable victim

It was Lenon who identified Mr Pajich as a possible victim, the court was told. She met Mr Pajich while they studied at a vocational college and he became friends with her 14-year-old son.

In the weeks before the murder, Lilley and Lenon shopped at a hardware store on three separate occasions to buy goods including a circular saw, bleach, cement, a drop sheet, a large plastic barrel and some acetone.

The day before Mr Pajich was killed, they bought a total of 100 litres of hydrochloric acid from separate stores in Perth.

Part of one text message that police say was sent by Lenon to Lilley

Mr Pajich has been living as a boarder with Adrienne Reid since 2016. They met through their church. On 13 June, 2016, as they ate breakfast, Lenon phoned Mr Pajich to invite him to her house.

Ms Reid dropped him to meet Lenon and Lilley at a shopping centre before 10:00. CCTV showed Lilley and Lenon meeting Mr Pajich in the car park and driving away.

Mr Pajich thought he'd be swapping computer games with Lenon's son as he walked towards the house, which had a sign reading "Elm Street" on the gate.

The court heard that once inside, Lilley jumped Mr Pajich from behind and tried to garrotte him but the garrotte snapped.

Then, Lenon pinned the 51kg (112lb) teenager on the floor as Lilley stabbed him three times - twice in the neck and once in the chest.

"[Lilley] murdered Aaron Pajich for the euphoria and exhilaration of it," prosecutor James Mactaggart later told a jury.

Police say the attack most likely took place in Lilley's lounge, where a large square of carpet was cut from the floor in what they say was an attempt to remove blood stains.

Police say carpet was cut from the floor beneath where a rug is seen in this photo

The women moved Mr Pajich's body to a specially prepared room with a white-tiled floor that was lined with blue tarpaulins. It contained a gurney and a bright red utility cupboard when police found it.

If there was any plan to use the acid on Mr Pajich's body, it never happened. The women buried him in a shallow grave in their backyard.

Lenon's son later unwittingly covered his friend's grave with concrete and red indoor tiles after the murder.

CCTV clue

Ms Reid reported Mr Pajich missing on 14 June after he did not come home, wasn't at his usual haunts and did not return calls or texts. After days with no sign of Mr Pajich, police appealed for public help and delved deeper, checking his phone records.

They found the last call he received came from Lenon, and that led them to her house on 20 June.

A subsequent search revealed the body, dozens of knives, a bone saw, scalpels, a machete, and an alphabetised handwritten list of torture techniques.

Then, incredibly, police found CCTV evidence recorded by Lilley's own home security set-up. Wary that her collection of motorcycles might come to harm, Lilley had installed a motion-sensing CCTV system at four points outside the house.

A set of knives and a bone saw (left) recovered from the house

The footage captured Mr Pajich entering the back door of the house with Lilley and Lenon about 10:00 on the day he died.

About 10.30, it filmed Lenon leaving the house and entering again carrying a large knife inside a sheath. The CCTV was later switched off.

Following their arrest, each woman accused the other of the murder. Lilley said she was sleeping when Lenon murdered him. Lenon admitted only witnessing Lilley kill Mr Pajich and helping to conceal the crime.

During the five-week trial, Lilley spent five days on the stand while Lenon remained silent.

She said the intense murder-themed exchanges she and Lenon shared was merely role playing for a new book.

Matthew Stray, who worked under Lilley at the supermarket, testified that she confessed the murder to him five days after Mr Pajich went missing but three days before his body was found, sounding excited as she described it.

Mr Stray said Lilley told him that "the police were so dumb" and would not catch her.

Horrified, Mr Stray intimated he may go to the police, but Lilley told him she may "have to make the problem go away", later sending text messages suggesting she'd made up the story.

Police say this room was sealed and concealed, and contained a cupboard, a gurney, a towel and a mop

Another co-worker, Jeffrey Burling, testified that Lilley told him she "wanted to be a serial killer and she wanted to leave her mark".

It took the jury just two-and-a-half hours to find both women guilty.

On Wednesday, after the sentencing, Mr Pajich's stepmother Veronica Desmond said she hoped the pair would "rot".

"I hope you live to regret what you've done," she said.

Jamie Duncan is a freelance writer based in Melbourne.