Emma Frizzell, a senior constable with the Australian Federal Police sexual assault and child abuse team (SACAT), appeared before an independent inquiry examining how the ACT justice system handled the high-profile case.
She was involved in investigating Ms Higgins' allegation that former colleague Bruce Lehrmann raped her in 2019, inside the Parliament House office of then coalition minister Linda Reynolds after a night out.
Mr Lehrmann denies the allegation.
In her statement to the inquiry, Sen Const Frizzell said she believed the legal test to charge a suspect was having a reasonable belief the evidence supported the prospects of a conviction.
But having watched inquiry hearings for the past few weeks, she realised she was wrong.
"I would concede that I don't have it right (and) what I've written in my statement is not right," she told the inquiry on Thursday.
Asked if there was still confusion among police about what the legal test to charge a suspect is, Sen Const Frizzel said: "Yes I would say that there is."
Director of Public Prosecutions Shane Drumgold previously told the inquiry he was concerned about what officers believed were the standard-of-proof tests required to charge someone.
Sen Const Frizzell, when asked about the relationship between police and Ms Higgins, denied investigators resented the former Liberal Party staffer for communicating with them through the ACT Victims of Crime Commissioner Heidi Yates.
But it made it difficult to build a relationship with Ms Higgins, she said.
"It allowed no communication, no contact. You can't build rapport or a relationship with someone you can't speak to."
The inquiry previously heard evidence Ms Yates assisted police, including organising Ms Higgins to provide additional evidence, which was beneficial to the investigation.
But Sen Const Frizzell said Ms Yates' involvement meant she could not build the type of relationship she normally would with a complainant.
The inquiry was told by AFP Detective Superintendent Scott Moller that SACAT is used as a "training ground for budding detectives" and many officers were "very young and inexperienced".
But he said investigators were dedicated and hard-working nonetheless.
Supt Moller said he was proud of his officers for pursuing Mr Lehrmann's prosecution despite holding personal beliefs there was not enough evidence to charge him.
While he originally thought there was not enough evidence, Det Supt Moller said his opinion changed when he read advice from Mr Drumgold that the prosecution should go ahead.
But he would not concede that his original view of the case was wrong or that investigators had lost their objectivity.
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