DNA evidence may have been omitted from criminal cases in Queensland because some samples weren't tested thoroughly, an inquiry has heard.
The probe, led by former judge Walter Sofronoff, is examining the state-run lab's 2018 decision to stop testing samples which contained tiny amounts of DNA.
Forensic scientist Alicia Quartermain retested some samples from sexual assault cases marked as 'insufficient for processing', and they returned DNA profiles.
"Some of these samples ...had got some good, usable DNA profiles," she told the inquiry on Monday.
"So to say that we're calling these samples insufficient for further processing: it's not correct."
Other scientists had similar concerns, she said, and that the very concept of DNA being insufficient for further processing was false anyway.
"It can always be processed further, whether or not we get a usable DNA profile at the end of it is the question, but we could always do more with those samples," she said.
Counsel Assisting Laura Reece asked her if she was concerned evidence that may be useful for the courts had been omitted from some criminal cases.
"Yes," Ms Quartermain replied.
She kept a record of the test results to alert superiors about her concerns in 2020, and again last year.
She said she wanted to continue retesting samples and her manager gave her approval to seek permission from senior management, but that wasn't given.
Ms Quartermain said she didn't receive an explanation about that refusal either.
"When it reaches that next person often things stop as opposed to getting support from that person, or sitting down and having a conversation around why that person thinks, 'no, this doesn't need to proceed further'," she said.
The scientist said that culture was a problem, and the episode made her feel like she wasn't trusted and was being prevented from doing a thorough job.
