No further consideration has been given to a potentially flawed DNA collection method despite Queensland Police being "on notice" that its efficacy is questionable, an inquiry has been told.
A problem with mould more than 10 years ago prompted the QPS to investigate whether swapping water to a 70 per cent ethanol mix, to wet DNA collection swabs, would result in faster drying times.
Experiments showed that ethanol dried up to six times faster than water, but did not appear to collect as much of the relevant biological material, counsel assisting the Inquiry into DNA Testing Joshua Jones said on Friday.
This could prove critical in the case of small stains on semi-porous surfaces, such as plasterboard, the inquiry was told.
"It's a case that no validation or verification has taken place, as at the time they decide to use ethanol," Mr Jones said.
"But even more egregiously is the fact that they are on notice that its efficacy is questionable."
The QPS had also swapped to rayon swabs in 2009 after an issue with not picking up DNA, Mr Jones said.
"Rayon swabs with 70 per cent ethanol were then commissioned into use without any further consideration, and have been in operation since 2010, some 12 years."
The inquiry was shown a 2008 email from managing scientist at the Queensland forensics lab, Cathie Allen, in which she said she had spoken to other scientists and they agreed "either distilled water or 70 per cent ethanol would be a suitable solution to collect blood".
Forensic biologist and director of South Australia's forensic lab, Professor Linzi Wilson-Wilde, prepared a report for the commission about the swab process.
"In my review of the literature, I haven't found any validation studies on rayon swabs with 70 per cent ethanol, and I can't find any evidence that it's been validated," she said.
Prof Wilson-Wilde said she was also unable to find any validation or verification done in Queensland from documents provided by the commission.
"I do have concerns about that particular combination," she said.
"It's not the worst, but it's also not the best."
Other types of alcohol have been shown to perform better as wetting agents instead of ethanol, she said.
Friday's hearing is expected to be the last of the long-running inquiry, with a final report to be handed to the Queensland Government on December 13.
