ACCUSED murderer Megan Jean Haines once allegedly told a boyfriend she "knew how to kill a person without being detected" by injecting them with insulin, a jury has heard.
The former aged care nurse wore a black suit jacket with her hair tied in a tight bun as she faced her first day of trial for the alleged Ballina murders of St Andrew's nursing home residents Isabella Spencer and Marie Darragh in 2014.
Crown prosecutor Brendan Campbell told Sydney Supreme Court on Monday a former boyfriend would be called to give evidence about a conversation he allegedly had with Haines while watching a crime show on television in 2009.
Mr Campbell said Haines had told her former partner the criminals on the "CSI-type" show were "all stupid" and she knew how to kill somebody and get away with it.
"It's easy," she allegedly continued.
"Insulin. Just inject them with insulin."
When pressed on why it would not be detected, Haines allegedly said: "Because the body continues to metabolise the insulin so it looks like natural causes" and "if you are good at injections, it won't even leave a mark".
Ms Darragh and Ms Spencer were found in comatose states with elevated insulin levels the morning they died.
Ms Haines has pleaded not guilty to murdering the two women.
The 12-juror panel was told Haines had only worked six shifts at St Andrew's nursing home when the two residents died.
Mr Campbell said Haines had a history of complaints from patients since she began working as a registered nurse in Australia in 2001.
She was on her sixth shift at St Andrew's on the night two residents died in May 2014.
"Within that time she had accumulated a number of complaints from residents," he said.
"(Former director of care) Wendy Turner spoke to the accused and advised her that there were complaints from three residents and that they would have a meeting about that the next Tuesday.
"And she reminded the accused of the reporting conditions to AHPRA (Australian Health Practitioner Regulation Agency).
"The next morning, members of the jury, two of those residents that had complained were dead."
Mr Campbell said staff initially suspected Ms Darragh, 82, and Ms Spencer, 77, had died from either heart attack or stroke.
Ms Spencer had previously suffered a severe stroke that left her with dense left-side paralysis, he said.
But the court heard blood tests revealed the two women had elevated levels of insulin, causing them to "go into hyperglycaemic shock, coma and death".
Mr Campbell said neither woman had been prescribed insulin and alleged they were administered "a drug they did not require, with the intention of killing them".
Defence barrister Troy Edwards said his client did not dispute insulin injections had killed both women but she denied administering insulin injections to either of them.
He questioned whether Haines had motive or was even aware Ms Darragh and Ms Spencer had made complaints about her.
A third woman had also made a complaint against Haines but had been found alive and well the next day, Mr Edwards said.
He added the alleged conversation years earlier with his client's boyfriend about how to get away with murder had little relevance.
Mr Edwards said he would ask the jury to decide whether it was just "about the circumstances of the television show" she was watching.
Mr Campbell said the court would hear evidence about a phone call police intercepted between Haines and a person called "Herman" on May 16 in which she allegedly implied she knew the women had been given the wrong drugs.
He said the message had been sent before experts and toxicology tests had determined insulin overdose was the cause of death.
Haines had "demonstrated knowledge that she could not have known, except that she was the killer", he said.
Mr Campbell also outlined a series of complaints that had followed Haines since she arrived from South Africa and started working as a registered nurse in Victoria.
The allegations related to inadequate nursing care and, once, a text message in which she allegedly threatened to access confidential patient information, Mr Campbell said.
He said Haines was the only registered nurse working on the night the two women died, and she was the only one of five staff on shift whose staff swipe card gave her access to the facility's medication rooms.
But he said a lightning strike had damaged the system and, while otherwise functional, it had not recorded which swipe card had opened any particular door.
CCTV allowed staff to monitor entry points to the facility but it did not record the footage.
Both Ms Spencer and Ms Darragh had medical issues but their conditions had been considered stable at their last check-ups, the court heard.
Mr Campbell said Ms Darragh, an avid Brisbane Broncos supporter, watched rugby league on TV the night she died.
Justice Peter Garling has sent the jury to nominate a foreperson during an adjournment, with defence barrister Troy Edwards to make his opening remarks when the court resumes.
Sydney-based Detective Sergeant Sergeant Gunn, who led the police investigation, was briefly called on to give evidence before the matter was adjourned.
The possible eight-week trial will resume at 10am on Tuesday.