Mark Sheridan Waden is being re-tried for the murder of former American beauty queen Priscilla Brooten, after the first trial was aborted on Tuesday due to juror misconduct.
Waden lived with Ms Brooten at the time of her disappearance in Brisbane's northern suburbs on July 5, 2018. Her body has never been found.
On Thursday the Brisbane Supreme Court jury heard from Ms Brooten's previous partner Steve Thompson, who provided her with ongoing monetary and emotional support until her disappearance.
Mr Thompson, who is based in London, began weeping when audio messages of an emotional Ms Brooten were played in court.
He said the pair had been in a relationship between 2011 and 2016 but had eventually separated due to Ms Brooten's lavish spending, which was putting pressure on Mr Thompson's finances.
However, he continued to offer support after the relationship ended and she began living with Waden.
In the weeks leading up to her disappearance, Ms Brooten showed signs of severe distress and sent images of herself to Mr Thompson after she had self-harmed.
Mr Thompson continued to provide financial and emotional support, including paying for Ms Brooten's therapy sessions.
The pair stayed in frequent contact via WhatsApp until July 6, the day after Ms Brooten was last seen.
At that point, she or someone using her phone - alleged to be Waden - began replying to Mr Thompson by text message instead.
When Mr Thompson asked if WhatsApp was broken, Ms Brooten, or a person posing as her, said it had been deleted.
He said he did not think the messages themselves were out of character, only the means by which they were sent.
Asked by prosecutor Andrew Walklate if he killed Ms Brooten, Mr Thompson said "no".
He told the jury it did not fully dawn on him that she was not an Australian citizen until after they had separated.
Earlier, the court heard how Ms Brooten had abruptly cut off communication with close family members in the US, including her daughter and mother, more than a year before she went missing.
The court also heard from Senior Constable Neil Ollenburg, from Queensland Police's Missing Person's Unit, who searched for Ms Brooten after she was reported missing by Mr Thompson on December 10, 2018.
Sen Const Ollenburg said he had run checks with Centrelink, Border Force, financial institutions, airlines and hospitals, using up to seven different aliases used by Ms Brooten.
He said the checks showed no proof of life after the date she was last seen.
The court also was told Waden had arranged for an earth-moving business to dig a trench measuring four metres long, 40 centimetres wide and 90cm deep the day after Ms Brooten's disappearance.
On May 5 and May 7, 2019, he allegedly dumped more than 800 kilograms of soil at the Nudgee tip after hiring an excavator.
The trial, before Justice Peter Callaghan, continues on Friday.
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