A senior detective who investigated Brittany Higgins' rape allegations has detailed the tense relationship police had with prosecutors and a victims support service as the case progressed.
Australian Federal Police Detective Superintendent Scott Moller faced cross-examination during an inquiry into how the ACT's justice system handled the matter.
Supt Moller was the lead officer who investigated Ms Higgins' allegation she was raped after a night out in 2019 by Bruce Lehrmann, a former colleague, inside the Parliament House office of then coalition minister Linda Reynolds.
Mr Lehrmann denies the allegation.
The senior officer told the inquiry ACT Director of Public Prosecutions Shane Drumgold was dismissive of police concerns there was not enough evidence to charge Mr Lehrmann.
"The team were of the view ... (Drumgold) was going to prosecute this matter, no matter what," he said.
Supt Moller said he wanted to get independent advice about charging Mr Lehrmann because he felt the chief prosecutor lost objectivity.
"I was disappointed that (the case) was going to go ahead, specifically when I thought there was insufficient evidence," Supt Moller said on Tuesday.
"Mr Drumgold continually, over many months, dismissed (investigators) propositions about this matter."
He said investigators were concerned about putting Mr Lehrmann before the court because of the "presumption of innocence".
The inquiry was previously told by Mr Drumgold that police had a passion for the prosecution to fail and pressured him not to charge Mr Lehrmann.
But Supt Moller insisted police were "absolutely professional" once the prosecutor had reviewed the evidence and charged Mr Lehrmann and they were committed to the investigation.
He said investigators felt significant pressure from the media, public, prosecutors and within the AFP to progress the matter.
Top silk Mark Tedeschi, representing Mr Drumgold, suggested the relationship between police and prosecutors began to deteriorate as early as 2021.
He said this occurred after a report the ACT government did in collaboration with the DPP and other agencies found police could be undercharging in sexual assault matters.
Supt Moller said he "supposed" the report contributed to issues between police and prosecutors.
"Certainly the (police) sexual assault team was taken aback by the report. They were hurt ... they were upset because it pointed to their professionalism," he said.
"(But) I don't agree ... that Mr Drumgold was the driving force behind (the report) and that police were upset with him because of that ... from a policing perspective, we don't shy away from criticism."
In a statement to the inquiry, Supt Moller said the involvement of ACT Victims of Crime Commissioner Heidi Yates during the investigation was inappropriate.
Ms Yates acted as a support person for Ms Higgins and accompanied her to the trial.
Supt Moller said he found Ms Yates' involvement frustrating and cumbersome and her position intimidated officers.
Ms Yates acted as an intermediary for Ms Higgins which Supt Moller said made it difficult for police to contact her.
"The investigators appeared to be nervous when they were interacting with Ms Yates. They weren't comfortable," he said.
"They felt often that Ms Yates was speaking for Ms Higgins and not allowing Ms Higgins to speak."
Mr Tedeschi suggested the prosecutor's office was not told Ms Yates would be interviewed by police because officers knew there could be objections to that.
Supt Moller said he did not consider that if Ms Yates was interviewed it could have resulted in her being a witness in the case and she would therefore no longer be able to provide support to Ms Higgins in court.
Ms Yates is expected to be called as a witness to the inquiry.
