Mark Sheridan Waden allegedly killed Priscilla Brooten and disposed of her body before dumping her at a Brisbane rubbish tip nearly a year later.
Waden is also accused of using the US woman's mobile phone after she went missing, posing as her in texts and giving it to a new girlfriend before it was seized by police.
Ms Brooten, an American citizen who was staying in Australia illegally, Â vanished from the home she shared with Waden in Brisbane's northern suburbs on July 5, 2018, a jury heard.
Almost eight years later, Waden faced Brisbane Supreme Court on Monday as his murder trial began.
Ms Brooten, 46, was not reported missing until December 2018.
Her body was never found.
Waden told police and acquaintances she had left him, may have returned to the US or been taken by immigration officials.
Prosecutor Andrew Walklate on Monday outlined to the jury what he said was a compelling circumstantial case connecting Waden to Ms Brooten's murder.
He said that on the night of her alleged murder, Ms Brooten had confronted Waden over evidence of an affair he was having with a work colleague.
Waden is accused of killing Ms Brooten during the argument on July 5, 2018.
The next morning, Waden allegedly organised via a mobile marketplace for someone to dig the trench at his home that day, saying he couldn't wait days or weeks.
Nearly two weeks after Ms Brooten's alleged murder, her phone was offered to Waden's new partner after a factory reset and a later police inspection confirmed it was Ms Brooten's, the jury heard.
Waden is accused of returning to his property and digging up about 800kg of soil and dumping it at a Nudgee rubbish tip over May 5 and May 7 2019.
Mr Walklate suggested to the jury that Ms Brooten's remains may have been dumped there along with the soil.
Defence barrister James Godbolt said the case against his client was based on conjecture, speculation and supposition.
"How was she killed? The prosecution can't say," he said.
"There is not a single piece of evidence that suggests the area excavated was used as a gravesite."
He said while it was clear Waden had told various lies, there were reasons for him doing so and none of them implicated him in Ms Brooten's disappearance.
Mr Godbolt suggested Ms Brooten may even still be alive.
He said it was clear Ms Brooten was unhappy and was in the country illegally after managing to stay under the radar for many years.
"Perhaps she managed to leave the country under another name, perhaps she's still in the country living under the radar, perhaps she committed suicide."
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