Evidence heard on Monday on the first day of a commission of inquiry's public hearings revealed changes to DNA threshold limits were introduced in part to save the laboratory time and money.

The hearings follow the release of an interim report that identified serious shortfalls in testing thresholds affecting an unknown number of major crimes including murder and rape.

The report revealed the state-run laboratory did not test samples under a certain threshold, which could have identified partial or full DNA profiles.

The report uncovered up to 10 per cent of samples classified as "insufficient for processing" that, if further tested, may have led to positive identification or could have potentially changed the outcome of legal proceedings.

Shandee's mother Vicki Blackburn, who attended the hearing, said she was relieved the inquiry had started, and she was one step closer to answers.

"There's a relief that we are on the path to getting the truth and justice for Shandee," Ms Blackburn said outside court.

"We have already heard evidence that we weren't aware of ... so it's going to be enlightening for everybody.

"This is the tip of the iceberg, and I think we're just about to see what's underneath."

Key witness forensic scientist Kirsty Wright said she was "quite scared" about what the evidence would reveal.

"I think this is the most important event the criminal justice system in Queensland has ever seen," she said.

Dr Wright feared the inquiry and its aftermath would be deeply traumatising for the victims and their loved ones.

"But I think it also gives them hope that their samples will get the attention that they deserve, so hopefully it's another opportunity for them to get justice as well.

"It's a difficult time for everyone, and there are really no winners.

"I think there's a lot more to come. I'm quite scared about the extent of trouble that's been in the lab."

The inquiry was told threshold testing changes were first proposed in 2017 as a way to increase testing speed and lower costs.

"We don't have to spend money testing these samples, and we can spend the money somewhere else, and we can use the time somewhere else. They say it six times (in the report)," Mr Sofronoff summarised.

"Yes," the counsel assisting Michael Hodge said.

"They all effectively say ... it will be faster and it will require less resources so it will improve turnaround."

Laboratory staff members testified to raising serious concerns about changes to the testing regime, only for feedback to be ignored.

"My expectation being a member of the management team ... would be that our perspective on the project would be seriously considered and discussed," senior scientist Kylie Rika told the commission.

However, unless the feedback was overwhelmingly positive, Ms Rika said it was not well received and created a difficult working environment.

"In my view, the culture of the lab around that time was quite toxic."

Senior police are also expected to testify that the success rate of forensic testing was "grossly minimised" by the higher thresholds.

One senior officer, who holds scientific qualifications, will tell the commission he first questioned DNA results during a murder investigation.

"In 2018, dealing with the DNA results from a particular murder investigation caused the inspector to question the results of some samples which had originally been reported as DNA insufficient for further processing," Mr Hodge said.

"And upon retesting, three of the four samples provided a DNA profile."

Two senior staff members at Queensland's forensic lab have been stood down pending the full results of the inquiry.

The commission's full report is due in December.

Australian Associated Press