The Illawarra Mercury can reveal police investigated the death of Snibson's elderly neighbour Judith Palinkas in the wake of her arrest for the murders of Kathryn McKay and Greg Hosa in January 2006.

Ms Palinkas officially died of bowel cancer in April 2003.

However, Snibson's ex-husband Paul now suspects she may have laced Ms Palinkas' meals with dog tranquillisers to accelerate her death.

Ms Palinkas changed her long-standing will on her deathbed, leaving her small A-frame house in Calymea St to Snibson after she allegedly promised to always care for her beloved dogs.

Within days of Snibson moving into the house, most of the dogs were sold or put down.

Ms Palinkas' sister Ailsa Woollard has confirmed the last-minute change to her sister's will and said she too had suspicions about what happened.

The investigation into the 76-year-old's death was cut short as her remains were cremated, leaving no way to discover if cancer was her only killer.

Mr Snibson, a soldier, claims his ex-wife had asked him about post-mortem examinations and knew there would be no autopsy on Ms Palinkas because she had a terminal illness.

In a macabre twist, the house Snibson inherited from Ms Palinkas became the scene of the grisly murders of Ms McKay and Mr Hosa.

Snibson and her accomplices tied up the couple and left them for hours in the house before killing them and burning their bodies.

Adding weight to the suspicions are allegations raised in the NSW Supreme Court that Snibson had spent a decade planning to kidnap, assault and kill various people.

During her sentencing hearings, Crown prosecutor Paul Leask aired allegations that after Snibson moved into her first home in Calymea St, she had offered a friend $30,000 to help "in seeing an old lady who lived across the road was dead".