A Gold Coast man accused of murdering his wife owed millions in returns to investors after becoming embroiled in a stock market scheme, a court has been told.
Andrew John Cobby is standing trial for the murder of Gaylene Cobby - known as Kym - who was found beaten and choked to death outside her Worongary home in the Gold Coast hinterland on November 12, 2017.
The 59-year-old has pleaded not guilty to killing the woman he called the "love of his life".
The couple had been married for more than three decades, but mostly lived apart from 2003 onwards.
Hector Bonelli met Cobby when he invested in the trading scheme.
He admitted he and his partner sent letters of demand to Cobby, claiming they were owed more than $7 million.
But after continued delays in the promised returns, Mr Bonelli secretly began taping his dealings with Cobby.
During the recordings, Cobby repeatedly promises the money will be paid in full - an offer Mr Bonelli did not believe.
"Of course not, there was no money," he said.
"I made the recordings to protect myself, we knew we were never going to get our money back."
Although Mr Bonelli said Cobby lied to him repeatedly, under cross-examination he insisted he and Cobby had a "good relationship".
He denied being frustrated and angry over the financial loss, saying he was "always nice, always polite".
"I was not worried about the money that I lost, I was worried about other people's money.
"I wanted to get their money back."
During the recorded conversation, Cobby suggested ways to hide their returns to avoid being penalised by paying tax.
"You don't need to talk to a lawyer or an accountant, I have all the options," Cobby stated on the recordings.
After Ms Cobby's death, her husband told police the couple had been threatened and faced demands for millions of dollars.
"I have four individuals trying to extort money, but I couldn't pay them," Cobby said during his police interview.
Cobby has admitted being at the hinterland property where his wife was killed but says he ran away into the bush when they were both assaulted by an unknown assailant.
The trial continues before Justice Peter Callaghan.