A senior detective who investigated Brittany Higgins' rape allegation has admitted police made a mistake providing sensitive counselling notes to prosecutors and defence lawyers.
"That's the bottom line, we shouldn't have handed them over and it's a mistake that we made," Australian Federal Police Detective Superintendent Scott Moller told an independent inquiry on Monday.
Supt Moller was involved in investigating Ms Higgins' allegation Bruce Lehrmann, a former colleague, raped her after a night out in 2019, inside the Parliament House office of then coalition minister Linda Reynolds.
Mr Lerhmann denies the allegation.
Supt Moller told the inquiry it was difficult to articulate the collective pressure on police from the public, media and within his own organisation for Mr Lehrmann to be served with a court summons.
"There was a significant amount of pressure. There was a real desire to expedite this process and get Mr Lehrmann before the court," he said on Monday.
The stress of the investigation had impacted many police officers, some of whom had to take leave from work.
The inquiry had previously heard a brief of evidence containing Ms Higgins' counselling notes was provided to both the defence and prosecutors.
Supt Moller said this should not have happened but police had been acting in good faith.
"No one specifically turned their mind to the counselling notes being served, it was part of the brief that went (and) the police and myself were acting in good faith, sharing the material we had,'' he said.
"Absolutely, I acknowledge that we shouldn't have done that."
Following this mistake, Supt Moller said he was concerned Director of Public Prosecutions Shane Drumgold was trying to "collect evidence" in order to criticise police.
"It caused me quite a lot of concern for myself and my investigation team, so much so that we continually second-guessed ourselves about what we were doing and how we were doing it," he said.
Mr Drumgold told the inquiry he believed police had a "passion" for the prosecution to fail and criticised their decision to interview Ms Higgins for a second time.
But Supt Moller stood by the decision and said officers had an obligation to investigate inconsistencies in a complainant's account.
Officers were concerned by some of the evidence given to them by Ms Higgins and wanted to clarify this through a second interview.
"It's incumbent upon us as investigators to do the most complete and comprehensive job we can and that's what we try and do," Supt Moller said.
"We've got to support and protect the victim, but we've also got an obligation to collect the evidence ... so it's an ongoing battle for us."
Supt Moller said the case had demonstrated the need for the police and victims' support services to develop policies and training procedures in order to work together better.
Mr Lehrmann faced a trial in the ACT Supreme Court in October 2022 but juror misconduct meant a verdict was not reached.
Prosecutors later dropped charges against Mr Lehrmann due to concerns about the impact a second trial would have on the mental health of Ms Higgins.
The inquiry was set up by the ACT government after accusations by police and prosecutors about each other's conduct during the high-profile investigation and trial.
