Murdered wife thought husband was cheating

In the months before a Sydney woman was allegedly murdered by her husband, the pair had been sleeping in separate bedrooms and she thought he was cheating on her, her daughter says.

Tony Thao Do is accused of murdering his 54-year-old wife Kim Lien Huynh, who died on September 13, 2012 from a combination of neck compression and sharp and blunt force injuries to her head.

He has pleaded not guilty.

His trial has already heard how Ms Huynh's daughter Aminda had come home that night from work, cooked dinner, watched television and texted friends.

It wasn't until later, when she had turned on lights in the stairway of the Cabramatta home and illuminated the front room that she saw her mother's body, she says.

Aminda, 22, cried on Thursday as the Triple-0 call, which she made shortly after the discovery, was played to the court.

"It's my mum ... she's um, she's um ... She's not moving," Aminda is heard saying.

As her voice becomes increasingly high-pitched, she tells the operator, "I think she has been here for a while and I haven't noticed".

When the operator tells Aminda to go toward her mum and check to see if anything is blocking her airway, she cries, "I really can't do this, I really can't do this.

"Why is this happening? I don't understand."

Aminda told the court that when she eventually touched her mother she was "freezing cold".

She said when Do first came to live with the family in September 2011 it was clear they cared for each other.

"They were always together," she said.

But four months before her death, they were no longer sleeping in the same room and her mother began locking her bedroom door.

Aminda said she heard her mother get angry at Do for not doing enough around the house.

"She thought he was cheating on her via the computer," she said, adding they fought about how much time he spent on it.

She would say, "he's talking to other women" and "you can go back to America ... I have no use for you anymore".

Under cross examination by Do's barrister Craig Smith, Aminda agreed that at the time, her mother was also short-tempered towards her.

The trial continues.