The evidence surfaced on the first day of public hearings on Monday at the inquiry headed by Walter Sofronoff after an interim report delivered last week identified serious shortfalls in testing thresholds.
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.
Queensland police are reviewing criminal cases potentially affected between 2018 and June 2022.
Concerns were raised about the lab in relation to the investigation into the murder of Shandee Blackburn, a young woman killed at Mackay in 2013.
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.
The inquiry was told threshold testing changes were first proposed in 2017 as a way to increase testing speed and lower the 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," council 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 are expected to testify to raising serious concerns about changes to the testing regime.
Senior police are also expected to give evidence 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 of Inquiry into Forensic DNA Testing in Queensland will hold public hearings from next Monday.
The full report is due in December.
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