Man told operator 'I killed my wife'

When a constable ran up flights of stairs to a flat and asked the occupant if he had called police, the man replied: "Yes, I killed my wife".

"He was surprisingly calm," Michael Outzen - now an acting sergeant - told a NSW Supreme Court jury on Thursday.

Shahab Ahmed, 38, has pleaded not guilty to murdering his wife, Khondkar Fariha Elahi, 29, in their Parramatta unit on February 18, 2017.

Sgt Outzen said he rushed to the address in a police car with flashing lights and sirens after being told a caller said he had killed his wife.

The triple-zero call was played to the jury and began with Ahmed saying: "I killed my wife" before he gave his address, name and date of birth.

He said he had used a knife and "she is in the bed".

"How long ago did it happen?" asked the operator.

"Just a couple of minutes ago," he replied.

He said she wasn't breathing and an ambulance was not needed.

Ahmed said his wife had had an affair with one of his friends a few years ago and had said it was over, but "I checked her phone today".

Sgt Outzen said when he entered the flat Ahmed said his wife was in the bedroom, before the officer told him to get on the kitchen floor.

"He was very calm, very slow and concise," he said.

He could see blood on Ahmed's pants and when he went to the bedroom, saw a female lying on the mattress covered in blood.

"The woman was wearing a white dress almost completely covered in blood."

A knife was on the floor as well as a bowl containing cigarette butts.

Detective Senior Constable Brett Starr recorded Ahmed at the scene on his phone after telling him he had the right to silence.

The jury was played the recording in which Ahmed said he and his wife had argued.

She had had an affair with his friend Omar Khan about two years ago but told him it was over.

"We stayed separated for a couple of months and I went to my country," he said.

She told him maybe they don't have a future together because she thought her husband could not trust her anymore.

"I checked her phone and she still has a relationship with him and I killed her," Ahmed said.

The trial continues before Justice Natalie Adams.