A Sunshine Coast woman who admitted to dumping her partner's headless torso and setting it on fire is arguing she acted in self-defence, a Brisbane court has heard.

Lindy Yvonne Williams pleaded not guilty to murdering George Gerbic but guilty to interfering with a corpse at the beginning of her trial in the Supreme Court in Brisbane.

The 66-year-old's headless torso was discovered on fire on the side of Cedar Pocket Road, near Gympie, in September 2013.

The court heard the cause of Mr Gerbic's death could not be determined.

In his opening address, prosecutor Todd Fuller QC told jurors it was a "tedious and time-consuming" task for police to eventually identify the remains 10 months later, via a prescription drug found in his system.

Ms Williams was living a lie after the death of Mr Gerbic, the court heard. ( Facebook: Lindy Williams )

The court heard when police originally attended Ms Williams' home in July 2014, she told them Mr Gerbic was overseas.

"She told them that George Gerbic was in fact in Rio at the World Cup, that they were ex-partners, that he had had some emotional problems and needed some time alone," Mr Fuller said.

The court heard after more investigations, police returned to interview Ms Williams, who had changed her story and said the pair had a fight.

"She told them George Gerbic had returned home angry … he'd been struggling with his own bisexuality and struggling with dealings with his ex-wife," Mr Fuller said.

The prosecution told the court Ms Williams said Mr Gerbic became angry when she suggested he stay away from his ex-wife and that he had attacked her with a steak knife.

"[She told police] he slipped on blood on the floor and fell backwards and hit his head," Mr Fuller said.

A burnt towel found with Mr Gerbic's charred remains at Cedar Pocket. ( Queensland Police )

The court heard Ms Williams told police she left the house, rented a car and stayed in a motel for a few days before returning home.

"She told police that when she arrived, George was no longer lying on the floor where she had last seen him … so she thought he was okay," Mr Fuller said.

"She said she headed down towards the bedroom … and she discovered his torso, she says, wrapped in plastic on the floor."

Accused thought 'friend' may have cut up body: prosecution

The prosecution said Ms Williams told police she didn't know what to do with the torso, so she wrapped it in a tarp, dumped it on the side of the road and set the remains alight so police would find it.

Mr Fuller told the court: "When asked about the torso, she thought that a friend may have come and cut up the body.

"Lindy Williams had been living a lie and she continued to do so during those interviews."

The prosecution also claimed Ms Williams accessed Mr Gerbic's bank account after his death and allegedly sent text messages and emails to family members, pretending to be him.

Ms Williams lied to police about Mr Gerbic's whereabouts, the court heard. ( Facebook )

Defence barrister Simon Lewis told the court Mr Gerbic was an impatient and "violent man", and his client had acted in self-defence.

"You will hear that my client told a lot of lies to a lot of people and as my learned friend described, she was living a lie. Yes she was," Mr Lewis said.

"This isn't a who-done-it. My client caused the death of Mr Gerbic, that's not what the trial is about.

"People lie for a lot of reasons … was she covering up, as my learned friend says, a murder, or was she covering up a killing that happened in self defence?

"Lying to police doesn't make you guilty of murder, that's all I ask you to be conscious of as you listen to the evidence unfold."

About 60 witnesses are expected to give evidence in a trial expected to last more than a fortnight.