Edmund Ian Riggs, 60, admits Patricia Anne died after he pushed her during an argument.

But he denies murdering his wife whose skeletal remains were found buried at their family's former home near Brisbane in 2016, 15 years after she died.

On September 30, 2001, during the last of many arguments that peppered their 17-year marriage, Riggs said Patricia laughed at him when he tried to make peace.

Riggs said his wife told him she'd found a list of escorts in a pocket of his shorts.

Then she revealed she'd had numerous affairs with men she had met through swim coaching and at nightclubs

Her attitude was, "anything you can do, I can do better".

"I was in shock. That's the first I'd heard of it. I started crying," he told his murder trial in the Brisbane Supreme Court on Thursday.

"She started berating me. 'I wasn't a man. I was sickly'.

"I pushed her and she died as a result of that."

"She went backwards and down and the back of her head or neck or something hit the ... foot of the bed.

Patricia started convulsing and when she stopped, she was dead. He felt blood behind her head.

"My brain's just exploded," Riggs said.

"I knew if I killed her I'd be going to jail for the rest of my life.

"I had four kids who just lost their mum. I didn't want them to lose me as well.

"I didn't want them to be orphans."

Riggs carried his wife's body downstairs, put it in his car and drove around.

He buried her in a shallow grave on the outskirts of Caboolture before cleaning her blood from their bedroom with disinfectant.

He dug up her remains a few years later after seeing heavy machinery at the site. He reburied them at the family home at Redcliffe, north of Brisbane.

They were found by a new owner who was concreting behind a shed.

Riggs pleaded guilty this week to interfering with his wife's corpse.

For 18 years he lied that his wife had walked out and he didn't know where she was. He also filed a missing persons report.

The prosecution claims he deliberately killed her, suggesting, during cross-examination, he was motivated by complaints about his lack of financial contribution to the family and her affairs.

Crown prosecutor Todd Fuller QC suggested the killing happened a different way.

"I suggest to you that you did something to her that caused her death and what you did to her has been covered up by your choice in disposing of her body," he said.

The trial continues.

Australian Associated Press