THE husband of Julie-Ann Leahy began a sexual relationship with her teenage sister a short time before Ms Leahy and her best friend Vicki Arnold were found dead, an inquest was told yesterday.
In one of Queensland's most baffling murder cases, the bodies of Ms Leahy, 26, and Ms Arnold, 27, were discovered in a four-wheel-drive in remote bushland on the Atherton Tableland, west of Cairns, on August 9,1991.
In sensational claims, Ms Leahy's sister Vanessa Stewart yesterday revealed how she was coached by Alan Leahy to make false statements to police and provide him with an alibi.
Asked by counsel assisting Coroner Ralph Devlin if she thought Mr Leahy was involved in the deaths, she replied: "Yes. I believe he was."
Yesterday Ms Stewart told the inquest into the deaths of Ms Leahy and Ms Arnold how her sister's husband had sex with her for the first time just one week after the pair went missing.
Months earlier Mr Leahy, a carpet-layer, had begun his sexual advances on the 15-year-old schoolgirl.
"He began instructing me in how to sexually please him," Ms Stewart, now 36, told the packed Cairns court room.
She claimed Mr Leahy first touched her while her half-sister Mrs Leahy, who was 10 years older, was in hospital with the couple's newborn baby in February 1991.
"I was innocent, naive, vulnerable," Ms Stewart said, describing her feelings for Mr Leahy as "misdirected teenage love".
She provided him with an alibi for the night the women went missing on an alleged fishing trip on July 28,1991.
"It was the first time he'd ever come into my room. He woke me in the middle of the night. I said: 'Where's Jules?' He said: 'She's gone. She's gone fishing.'
"I felt very controlled by Alan. He warned me not to brainwash the other kids with all the unanswered questions."
Two weeks after they vanished, the bodies of the two best friends were found with gunshot wounds in Mrs Leahy's Nissan Patrol.
Senior police at the time in two inquests and six police internal reviews have ruled the deaths as murder-suicide. The inquest has heard how police contaminated the crime scene on the remote Cherry Tree Creek, 14km from the family home, ruining any hope of using physical or forensic evidence.
In a tear-filled account, Ms Stewart said she broke her silence on the affair with Mr Leahy because she wanted "justice and peace" for herself and her family.
"This is an injustice. Not just the trauma for the family, the horror of how they died, or the police inability to do their jobs ... but a systemic failure." Ms Stewart told the inquest she felt sorry for Mr Leahy. "I don't hate him. Despite the abuse and how much he hurt me over the years."
Mr Leahy is due to give evidence today.