Brian Crickitt, 63, hugged and kissed his new wife, Julie, and tearful daughter before he was led away in handcuffs by correctional officers on Thursday morning.

After a more than two week trial in the NSW Supreme Court, Justice Clifton Hoeben found that Crickitt injected his wife Christine Crickitt, 61, with the fatal dose of insulin in their home, in Woodbine, in Sydney's south-west, between December 31, 2009, and January 1, 2010.

The Crown's case was that Crickitt drew on his skills as a doctor to kill his wife, knowing that insulin cannot be detected in the body more than 24 hours later and that it would be highly unlikely that an autopsy would be carried out on New Year's Day.

An autopsy was not carried out until January 2, 2010 and no cause of death could be determined. It was months later that investigators noticed a distinct small red mark on Mrs Crickett's bottom in post-mortem photographs.

Outside court, Mrs Crickett's eldest daughter from her first marriage, Tracey Wiggins, said she thought she knew Mr Crickitt and it was "beyond words" to explain the pain her family had endured.

"The sadness never goes away but what we have learnt is to appreciate life and to appreciate our mother even more for the many good things she taught us," Ms Wiggins said.

The trial heard that in the days before he killed his wife, Crickitt searched "intentional insulin overdose" on Google and wrote a prescription for fast-acting insulin under a patient's name that he filled himself at a Campbelltown pharmacy.

Crickitt, the court heart, was treating his wife for some of her illnesses and either forcibly injected her with insulin or convinced her it was medication that she needed.

Justice Hoeben found that, without an official cause of death, Crickitt's improper procurement of insulin was the "indispensible fact" that connected the medication to the death of Mrs Crickitt.

"I have concluded that his reason for writing the prescription and presenting it to the pharmacy had no legitimate basis in his practice as a medical practitioner. I find that the accused acquired the NovoRapid insulin for the purpose of administering it to the deceased," he said.

Justice Hoeben accepted that the primary motive for the murder was Crickitt's desire to be with Linda Livermore with whom he was having an affair, and his increasing dislike of his wife. The trial also heard that he would be eligible to claim more than half a million dollars of his wife's life insurance.

In an interview with police, Crickitt said that, on the evening of his wife's death, they had fought and he had packed some clothes, went for a drive and pulled over near a park and fell asleep.

He said he had then called his "friend", Ms Livermore, but denied that there was an intimate relationship with her.

But in a second interview, Crickitt confessed to police that he had lied about his relationship with Ms Livermore and said that, after the argument with his wife, he had driven straight to her home and spent the night with her.

He said he arrived home on New Year's Day to find his wife dead on their bedroom floor.

The trial heard that Crickitt made three calls to Ms Livermore, and received a phone call from her, before calling triple zero. Days later, he was seen holding hands with Ms Livermore when the pair visited Glebe morgue, where Mrs Crickitt's body was.

Crickitt's barrister Tim Gartelmann, SC, argued that it could not be proven beyond reasonable doubt that an injection of insulin was the cause of Mrs Crickitt's death or that insulin was in any way involved in her death.

Mr Gartelmann also contested the motives for the murder put forward by the Crown, arguing that the financial benefits were limited and there was no apparent reason why Mr Crickitt would simply not leave his wife to be with his lover.