'Murderer, terrorist': Why Bhanu Kirkman is arguing he's not guilty of Bellambi mum's murder

Kirkman forced his way inside Mr Powell's Lorking Street house just after 11.40pm on October 4 last year and repeatedly plunged a knife into her chest and back and slashed at her neck.

Ms Powell died at the scene. Her body was found by a friend early the next morning.

Kirkman was still carrying the blood-stained knife when he was arrested in Maitland four days later.

He immediately confessed to the killing, telling police he was part of the Indian military and was "on a mission" to "assassinate" Ms Powell, who was one of America's most wanted known terrorists.

Details of the fatal fantasy, as well as Kirkman's transformation from primary school captain to delusional killer, were laid bare in the NSW Supreme Court on Tuesday as the 30-year-old pleaded not guilty to murder on the grounds of mental illness.

Kirkman was adopted as a young boy and lived in Chippendale before the family moved to Thirroul, where he was a popular student known for his sporting achievements.

He was named school captain in Year 6, then went on to high school at Macarthur Anglican College near Campbelltown, where he played on the school's soccer team.

Kirkman began smoking cannabis from the age of 14 and by 18 had moved onto regular use of LSD. This affected his studies and he dropped out of university. By the age of 23, he'd started using ice. Kirkman began showing signs of mental illness in his late teens and had spent time in psychiatric facilities, including a three-month stay at a well-known hospital in Orange, during the past decade.

Kirkman met Kristie Powell in 2014. The following year, she employed him in her dog grooming business for several months but their friendship soured and the pair parted ways.

Soon after his employment came to an end, Kirkman began bombarding Ms Powell with disturbing messages on Facebook, sometimes more than 100 a day, including one which read "die Kristy, die".

Ms Powell took to Facebook in early 2018 to vent her frustrations, labelling Kirkman a "stalker" who had become "obsessed" with her, but also dismissed concerns from friends that she might be in danger.

Around the same time as Ms Powell's Facebook post, Kirkman began hearing voices in his head urging him to act.

He formed the belief Ms Powell had kidnapped him from his mother as a child and that she was an international terrorist responsible for blowing up the Twins Towers in New York in 2001.

On October 2, Kirkman purchased gloves, a knife and an interstate train ticket from Melbourne.

Two days later he was Sydney bound. He got off at Campbelltown, made his way to Wolli Creek, and then down to Corrimal, arriving at 11.06pm.

Meanwhile, Ms Powell had had two friends over that night, the last one leaving at 11.20pm. Kirkman arrived at her house at 11.40pm.

He kicked in her front door, forced his way inside her bedroom and stabbed her to death.

He then walked back to Corrimal Railway Station and caught a train to Port Kembla where he discarded his outer clothing. He caught a train back to Thirroul and went to see an old friend. The pair had "coffee and toast" and talked about football before Kirkman returned to Sydney at dawn. He then fled north to Maitland.

It's rare police get an on-the-spot confession, especially for murder, but Bhanu Kirkman was keen to share that day.

"Yeah, I killed her, it's all legit," Kirkman said as soon as he entered the interview room.

"I'm Indian military, check it all out. I can give you my number. She's the eight of Clubs, it had to be done".

The reference, which Kirkman later changed to be the "Nine of Diamonds", is understood to mirror America's well-known technique of using a deck of playing cards to help US troops identify targets in President Suddam Hussein's government during the 2003 invasion of Iraq.

In the interview, described in court on Tuesday as "grandiose" and "delusional", Kirkman told police Ms Powell was a professional assassin and wanted terrorist who had killed 19,000 people.

He said he had been sent on a military mission to assassinate her as she was responsible for the 9/11 attacks in America.

"Ahh, the shot I have waited for. To rid the world of the Nine of Diamonds. That's what Kristie Powell is on the American terror list," he told detectives.

He also told police the Chinese special forces would soon be coming to rescue him and return him to India.

Kirkman sure all of his important information was written down in his ever-present exercise book.

It contained pages and pages of ramblings, including multiple bizarre and disturbing "death lists", which named individuals, groups and organisations to target.

Among those on the list were Ellen De Generes (American actress and talk-show presenter); Queen Elizabeth II; Alexander The Great and; The Sith (from Star Wars).

Ms Powell appeared at the top of the list, along with her address.

Meranwhile, Kirkman identified himself by several names in the writings, including "The Reaper", "The Sun at the Centre of the Universe" and "Legendary Twin of Outer Space".

Two prominent psychiatrists brought in to assess Kirkman ahead of his trial both diagnosed him with a schizophrenic-type illness which they said had shown little signs of improving despite Kirkman receiving medication in custody.

Dr Stephen Allnut and Dr Richard Furst both agreed that Kirkman was displaying strong signs of mental illness.

Dr Allnut diagnosed Kirkman with a chronic psychotic state of mind, noting his delusions of grandeur and auditory and possible visual hallucinations.

Dr Furst noted Kirkman was still hearing voices in his head despite the fact he'd been on strong medication for months when he saw him in mid-2019.

It lead him to conclude Kirkman was "quite incapable of appreciating his actions were wrong according to the standards of a reasonable person."

Justice Richard Button will deliver his verdict at 3pm on Wednesday.