An inquiry has questioned why key evidence in the deaths of several LGBTQI people was "lost or destroyed" by NSW Police, and if prejudice played a part.
Police have been unable to produce several pieces of evidence requested by the Sydney inquiry into hate crimes between 1970 and 2010, prompting a demand for an explanation.
Assistant Commissioner Rashelle Conroy said on Tuesday it was standard practice for police to dispose of evidence after a certain period of time, when it was deemed to no longer be useful by an officer in charge of a case.
She said the way in which evidence is handled by police has changed dramatically since then, and it is now digitised and catalogued indefinitely.
"You're looking at exhibits from 1976 when DNA wasn't available and at the forefront of the investigators' minds, so they would have a different mindset about the retention of exhibits," Ms Conroy said.
"Under today's standards, then absolutely, we would collect and retain that exhibit."
The inquiry probed the mindset of those whose decision it was to not continue holding evidence, even as forensic methods such as DNA analysis were opening new avenues for investigation.
"Would you agree that the careful gathering, labelling and retaining of exhibits is a critical matter for investigations?" counsel assisting the inquiry James Emmet asked.
Ms Conroy agreed it was important, and in relation to unsolved cases, such as many of those that are the focus of the inquiry, it became even more important with the passing of time.
The inquiry heard last month that in some cases, victims’ blood-stained clothing was never sent for forensic analysis, and other exhibits remained untouched in evidence boxes for decades or were simply lost.
“Conscious or unconscious bias could lead an investigator to be less careful or less professionally curious, or more indifferent to a victim that the investigator thinks of as unsympathetic,” Mr Emmet said.
“... given what we now know about the widespread bias, not just within the police force, but in the wider community in the 1970s and 1980s.”
The inquiry also heard it took NSW Police the better part of a decade to begin widely using DNA evidence, despite having earlier access to the technology.
DNA was first used in a criminal investigation in the UK in 1986, but did not become a standard investigative tool for NSW Police until much later.
"It migrated very slowly into the NSW Police Force investigative cycle," Ms Conroy said.
"DNA first became available to us in 1992, but ... it really wasn't until 1998 ... that we had an ability and a validated process to use DNA more routinely in investigations."
Several high-ranking NSW police officers are due to be quizzed at the inquiry over lost exhibits, incomplete records and investigative failures into unsolved LGBTQI deaths in the state.
Supreme Court Justice John Sackar will deliver his report next month.
