A retired accountant who strangled his wife told police she attacked him and he chose to silence her after being fed up with her nagging, taunting and bullying.
"He gave an analogy of a dog biting back," prosecutor Adrian Robertson said in the crown opening address to a NSW Supreme Court jury on Friday.
Engracio Songcuan, 74, has pleaded not guilty to murdering Erlinda Songcuan, his wife of 44 years, in the garage of their Woodcroft home in Sydney's west on May 2, 2020.
He does not deny strangling the 69-year-old but has pleaded guilty to the less serious offence of manslaughter.
The Crown has not accepted the plea.
Songcuan's barrister Brian Royce told the jury the issues in dispute involved the use of excessive self-defence and extreme provocation.
"This trial is about the accused's actions and in no way are we blaming the deceased, but we have to look at that conduct in that context," he said.
Mr Robertson said the Filipino couple had three daughters, and a son who died in about 1991.
Their daughter Catherine, who lived with them, would give evidence about arguments and how they moved into separate bedrooms in 2018 after her mother was operated on for cancer.
The relationship had deteriorated and divorce was on the table, while Ms Songcuan suspected her husband was having an affair and spending their money.
In the days before the death, their daughter witnessed "quite a heated argument" when her mother struck her father with some slippers and had a knife in her hand.
She would give evidence that her mother was screaming and hysterical, was using a slipper to try to get her father's phone and was moving a knife around in small movements.
After her mother showed her a birthday card addressed to Songcuan which she found in the garage, her father told her "there was never anyone else" and her mother was paranoid.
Her mother later showed her divorce papers signed by the couple and discussed how she found out about the affair.
"She said she found some lady's clothing and she showed Catherine a pair of the accused's underpants inside of which was a g-string," Mr Robertson said.
Songcuan told police someone had poisoned his wife's mind, she suspected he was having an affair, and would taunt and nag him as well as pull knives on him and hit him with a slipper when they were driving.
He said he moved bedrooms as "I am afraid she might kill me because she is keeping knives in our room".
On the morning he killed her, he said she barged into his room and was hitting him with a large item and smashed the TV remote, and he had to choose to silence her for a little bit of peace and freedom.
"Her face was a like a tiger," he told police.
He said they went into the garage so as not to wake their daughter, before he squeezed her throat for maybe 15 or 20 minutes.
"I think I overreacted but I decided better for me, instead of living a miserable life."
Mr Robertson said Songcuan then mocked up the scene to make it look like his wife had hanged herself.
The jury would have to decide whether they accepted what Songcuan told police about the relationship.
He submitted Songcuan carried out a "deliberte act of vengeance" and hadn't experienced a loss of control.
He cited what he told police and his actions at the time and immediately after, including covering the body with cloth and a cardboard box and writing three notes.
The trial continues before Justice Hament Dhanji.
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