The chief prosecutor in former Liberal staffer Bruce Lehrmann’s rape trial believes ACT police could be confused about the level of proof required to charge someone with an offence.

Director of Public Prosecutions Shane Drumgold gave a fourth day of evidence to an independent inquiry into how the territory’s criminal justice system handled Brittany Higgins’ rape allegations against Mr Lehrmann.

Mr Drumgold told the inquiry there were tensions between his office and police about the credibility of Ms Higgins but he believed many of the points raised by officers were not admissible in court.

This included a desire by police to find an expert who could give evidence about Ms Higgins’ level of intoxication on the night of the alleged rape.

“There is no recognised field of expertise of observing drunk people, you simply can’t do it,” Mr Drumgold said on Thursday.

“I was also aware that we were sitting on CCTV which observed the complainant consuming alcohol, so in my view … (even) if they could find somebody that would speak to it, it would fall at the first hurdle.”

Mr Drumgold said he sensed police thought he was being dismissive of the issues they were raising but he had tried to explain they would not be able to be used in court.

Attitudes of police during the investigation led Mr Drumgold to believe they had deliberately provided a brief containing Ms Higgins’ counselling notes to Mr Lehrmann’s defence team but he now believed it was “probably error”.

Mr Drumgold said statements from police to the inquiry have made him concerned about what officers believe are the standard of proof tests required to charge someone.

“Some of the senior officers suggest that a unified test has been adopted and disseminated and some of the less senior officers don’t appear to have embraced that test,” he said.

“A couple of them have annunciated some words that include ‘probable cause’ which is a term that one might see on a police (television) show because it comes from a (US) constitutional amendment.

“Probable cause is not known to me, at least in Australian law, so it seems that there’s a lot of words getting around (and) applied in different formats but it’s still very unclear what the actual test being applied is.”

Mr Drumgold said he had been aware for some time that there may be confusion among some police officers about what the level of proof required for them to charge is.

Inquiry chair Walter Sofronoff is examining how territory police, prosecutors and a victim support service handled Ms Higgins’ allegations.

Officers from ACT Policing and the Australian Federal Police are expected to give evidence to the inquiry, as well as Mr Lehrmann’s defence lawyer and journalist Lisa Wilkinson.

Source: AAP