Northern Territory Police was investigating Constable Zachary Rolfe for alleged perjury on another matter around the time of the fatal shooting of Kumanjayi Walker, but did not pursue the charge due to a lack of evidence, court documents show.
Earlier this month, a jury found Constable Rolfe not guilty of murder and two alternative charges over the death of the 19-year-old Yuendumu man, who was shot three times during an attempted arrest in November 2019.
Details about the perjury probe emerged after all non-publication orders relating to the trial were lifted last week, including material surrounding so-called "tendency" evidence.
Among hundreds of pages of court documents were files linked to an internal police investigation that was launched after a local court judge made highly critical comments about Constable Rolfe in May 2019.
When dismissing charges against Alice Springs man Malcolm Ryder, Judge Greg Borchers found Constable Rolfe's evidence lacked credibility and he said the officer had "lied".
Superintendent said perjury probe was 'short of the benchmark'
The court documents show that about a month after the Yuendumu shooting, the NT Police Special References Unit sent files from its perjury probe to another police unit seeking an opinion about the prospects of the case.
But after reviewing the files, Superintendent Richard Bryson from the Judicial Operations Section said there was no evidence to assist a prosecution.
He noted that a perjury conviction would require the prosecution to prove beyond reasonable doubt that the accused knowingly provided false testimony, if indeed the testimony was false in the first place.
He noted that Constable Rolfe had not been interviewed by the investigators and suggested "undue reliance" had been placed on the judge's findings.
Superintendent Bryson concluded there was "little in the way of cogent admissible evidence".
"My reading of the material on file more properly demonstrates that the member's actions as being unprofessional, not criminal."
He said unless further investigation yielded "persuasive evidence", he would not forward the files to the Office of the Director of Public Prosecutions (DPP) for its consideration.
"The resources of this office and that of the DPP to provide considered opinions are finite and should not be wasted reviewing material that clearly is short of the benchmark," he said.
Rolfe defended his actions after complaint lodged with Ombudsman
The perjury probe, which also related to another officer whose evidence had been criticised by Judge Borchers, was subsequently dropped in February 2020 because there was "no reasonable prospect of conviction".
However, the court documents show the investigation files were later forwarded to the NT Police Professional Standards Command to examine potential "disciplinary breaches and unprofessional behaviour".
The documents also include a statement made by Constable Rolfe in 2018 in response to a complaint lodged with the Ombudsman about the use of force against Mr Ryder.
In his statement, Constable Rolfe said his use of force was necessary, reasonable, proportionate, and appropriate.
He also said he had not activated his body-worn camera during Mr Ryder's arrest because the devices were relatively new to officers in Alice Springs at the time.
"I was still getting used to putting it on, my muscle memory hadn't developed and since then I now endeavour to use body worn camera at all incidents where police powers are used," he said in a statement on August 8, 2018.
