The Supreme Court was told on Tuesday that Katherine Foreman, 31, was murdered in the early hours of October 27, 2011 when a man and a woman broke into her home as she slept, emptied a bucket of petrol into her bedroom and set it alight.

"In quick time a ferocious blaze commenced," Crown prosecutor Chris Maxwell, QC, said in his opening address to the jury, sitting in Wollongong.

"She was unable to escape that inferno, although she clearly attempted to do so." Mr Maxwell said the location of Ms Foreman's badly-burnt body on a landing outside her bedroom demonstrated this was the case.

"The presence of debris in her airways in both lungs is in keeping with the inhalation of smoke and soot, indicating that the deceased had been alive and breathing during the fire," Mr Maxwell said.

The court heard that a fourth person, Wendy Evans, has previously pleaded guilty to murder over the crime, though the prosecution stressed this did not prove the others were also guilty.

Three people are now on trial for the alleged murder - Ms Foreman's former lover, Bradley Max Rawlinson, 40, a man he allegedly hired to help carry out the crime, Bernard Justin Spicer, 31, and Mr Spicer's girlfriend, Michelle Sharon Proud, 28.

The court heard that a crucial factor in the commissioning and carrying out of the murder was a love triangle involving Mr Rawlinson, Evans and Ms Foreman.

"Central to the offence, the Crown says, was an intimate relationship that existed between Rawlinson and Evans in the months leading up to the fire," Mr Maxwell said.

"Rawlinson had also been in an ongoing relationship with the deceased. There is evidence that they remained in regular communication, saw each other regularly and it appears were still intimately involved up until her death.

"Rawlinson told the police [after the alleged murder] that he had sex with the deceased on the Sunday night before her death." Nevertheless, Mr Rawlinson allegedly wanted the woman dead, the Crown said.

The jury heard that text messages from Mr Rawlinson's phone discovered by detectives after the murder revealed the "closeness" of his relationship with Evans as well as the "enmity and ill will ... which both of them had towards Ms Foreman".

In one message, Mr Rawlinson allegedly told Evans: "I want to be with you till we die. I hope you understand the various reasons why it needs to happen to her now. I love you."

The Crown alleges that this and other similar texts are evidence of a plot between the pair to kill Ms Foreman or cause her serious bodily injury or grievous harm - all of which constitute the crime of murder in NSW.

At the same time, Mr Maxwell said, a "campaign of deception was being orchestrated ... against the deceased, calculated to cause her fear".

The jury heard that in pursuit of this plan, the pair enrolled the help of Bernard Spicer and Michelle Proud, making payments of $2400 to the former through a friend's TAB account. The four were part of a "joint criminal enterprise" to murder Ms Foreman.

It was Mr Spicer and Evans, the Crown alleged, who purchased a bucket and a large water container on the night of October 26, filled them with petrol, drove to Ms Foreman's home on a quiet street in the Wollongong suburb of Corrimal and broke in using a key they had obtained.

The court heard that Evans had a last-minute text message exchange with Rawlinson before setting Ms Foreman's bedroom on fire. This text was subsequently deleted, but in an intercepted conversation after the alleged murder, Evans recalled it as saying: "You asked if she was asleep, I said 'yes', you said 'do it and get out'." The Crown said this recollection was part of a number of conversations in which Evans and Mr Rawlinson expressed concern that their text messages would be obtained by police and used against them.

Ms Proud was also said to have been concerned about being caught, telling a friend after the alleged murder "all BJ [Spicer] was supposed to do, like ... I said go in there, mess her up a bit, damage her face ... fuck her face so it can't be fixed up..." Mr Maxwell said this was evidence of her role in the joint criminal enterprise and her desire to see Ms Foreman seriously harmed. The trial continues.