"The team were of the view ... he was going to prosecute this matter, no matter what," Australian Federal Police Detective Superintendent Scott Moller said, in reference to ACT Director of Public Prosecutions Shane Drumgold.
Supt Moller was the lead officer who investigated Ms Higgins' allegation Mr Lehrmann, a former colleague, raped her after a night out in 2019, inside the Parliament House office of then coalition minister Linda Reynolds.
Mr Lehrmann denies the allegation.
The senior officer told the inquiry he wanted to get independent advice about whether Mr Lehrmann should be charged because he felt Mr Drumgold "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.
"I felt, in certainly the briefings I'd had, that Mr Drumgold had lost objectivity.
"Mr Drumgold continually, over many months, dismissed (investigators) propositions about this matter."
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 all the evidence and decided to charge Mr Lehrmann.
"We were absolutely committed to the investigation and trying to find the truth of the matter," he said.
"When I read Mr Drumgold's advice, I was satisfied that it was sufficient for me to move forward (with charges)."
Supt Moller was earlier questioned about a police decision to interview the ACT Victims of Crime Commissioner Heidi Yates, who acted as a support person for Ms Higgins throughout the investigation and trial.
He said police found it difficult having Ms Yates act as an intermediary for Ms Higgins in the investigation as they couldn't communicate freely.
"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."
Top silk Mark Tedeschi, representing Mr Drumgold, suggested the prosecutor's office was not told Ms Yates would be interviewed because police knew they may object.
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.
