Investigators were "nervous" around Victims of Crime Commissioner Heidi Yates and found her close involvement with Ms Higgins "upsetting", Detective Superintendent Scott Moller told an inquiry on Tuesday.

The independent inquiry is scrutinising the actions of police, Ms Yates and ACT Director of Public Prosecutions Shane Drumgold SC in the case of Bruce Lehrmann.

Mr Lehrmann has always denied raping Ms Higgins at Parliament House in 2019, when the pair were Liberal Party staffers, and the charge levelled at him was discontinued after a mistrial last year.

In his written statement to the inquiry, Detective Superintendent Moller described feeling it was inappropriate for a statutory office holder to act as a "support person" for an alleged rape victim.

He also wrote that he was "mad" at Ms Yates because he believed she was more interested in Ms Higgins pushing the #MeToo movement agenda than she was in the case against Mr Lehrmann.

Under cross-examination on Tuesday, Detective Superintendent Moller said police had found it "difficult" to speak to Ms Higgins because of an arrangement in which contact went through Ms Yates.

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Detective Superintendent Moller said this had been "upsetting" for investigators.

"The investigators appeared to be nervous when they were interacting with Ms Yates," he said.

"They couldn't communicate freely. They felt often that Ms Yates was speaking for Ms Higgins and not allowing her to speak."

Mr Drumgold's barrister, Mark Tedeschi KC, suggested to Detective Superintendent Moller during cross-examination that he had attempted to isolate Ms Higgins by having Ms Yates interviewed by police.

Mr Tedeschi claimed police did not have genuine reasons to take a statement from Ms Yates, and noted doing so had the potential to make her a witness in Mr Lehrmann's case.

Such a scenario would have forced Ms Yates to withdraw, at least in some respects, as a support person for Ms Higgins.

But Detective Superintendent Moller said he had authorised, or "supported", Ms Yates being interviewed because he believed there were "genuine lines of inquiry" to be investigated.

He told the inquiry Ms Yates could have given independent evidence about a photograph of a cocktail, which was purportedly taken before the alleged rape, and about a phone owned by Ms Higgins.

Detective Superintendent Moller also said he had never thought Ms Yates would have to withdraw entirely from supporting Ms Higgins, only that she might not be able to attend court before testifying.

His evidence continues. Ms Yates is expected to give evidence later in the inquiry, which is yet to release her written statement.