A man set to give "crucial" evidence relating to the alleged hit-and-run murder of a police officer has raised concerns about his safety.
Anthony Frances was to testify in a committal hearing for Skye Anne Wallis and Kari O'Brien who are charged with murder over the death of Senior Constable David Masters.
The 53-year-old officer died after being hit by a suspected stolen car while deploying a tyre deflation device on the Bruce Highway at Burpengary, north of Brisbane, about 3am on June 26, 2021.
The Crown alleges the vehicle was driven by 36-year-old Wallis, while O'Brien was a passenger.
Police spoke to Mr Frances soon after Sen Const Masters died as the two women had been at his house.
But Mr Frances gave a different version when testifying at a coercive hearing at the Crime and Corruption Commission (CCC).
Detectives learned the women washed clothes at his house, staying for a short time.
Mr Frances was expected to give evidence on the second day of the committal hearing in Brisbane Magistrates Court on Tuesday.
Instead crown prosecutor Dejana Kovac said he had serious concerns about his safety.
She handed Magistrate Peter Saggers a one-page affidavit, saying the contents would be self-explanatory and asking for an adjournment for police to investigate.
Mr Frances' concerns were consistent with those raised by other witnesses who had already testified but their evidence was not as crucial as his, Ms Kovac added.
An application to declare Mr Frances a special witness due to intimidation being likely, may be considered on Wednesday, enabling him to testify in a separate room to the court.
If he does not attend the proceedings, prosecutors are expected to apply for a warrant.
Wallis' barrister Malcolm Harrison said Mr Frances had spoken to police numerous times and been compelled to give evidence before the CCC.
"That is the occasion where he gave the evidence which forms one of the vital parts of the case against my client."
Mr Harrison said defence teams had not been advised of a complaint of any threat.
"There's a bland assertion that matters are being investigated - no one knows if a complaint has been made."
O'Brien's barrister Christopher Wilson is set to argue at the end of the hearing that there is insufficient evidence to commit his 27-year-old client to stand trial for murder.
She was granted bail in April after the Brisbane Supreme Court found the prospects of a murder conviction were not high.
The crown case is that Wallis is responsible for the death as she drove the car dangerously at or toward the officer or by acting with reckless indifference to human life, the court was told earlier.
Prosecutors argue O'Brien had a common purpose with Wallis to unlawfully use a car to avoid apprehension and the offence was a probable consequence.
The women are also facing one count each of unlawful use of a vehicle and arson, relating to the car being found burnt out.
The committal hearing is due to continue on Wednesday.
