Thousands of Queensland DNA crime samples went untested in controversial lab decision, inquest hears

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In its final day of public hearings, the Queensland Forensic DNA Testing Commission of Inquiry has heard thousands of crime scene samples were not passed on for testing following a controversial 2018 change.

The now scrapped decision not to process samples below a certain threshold – labeled “DNA insufficient for processing” or “DIFP” – has been at the center of the investigations.

It comes after weeks of public hearings examining the troubled state-run forensic lab.

The decision was made in 2018 and abandoned when the Queensland Government ordered the commission of inquiry earlier this year.

Counsel assisting the inquiry Susan Hedge today cross-examined expert witness South Australian Professor Linzi Wilson-Wilde, who told the inquiry that 4,000 samples were ultimately not tested each year.

Data provided by Queensland Health broke down how many samples were received each year and how many of the samples classified “DIFP” were actually processed further.

“When you look at the total samples received … is between 20,000 and 25,000 samples, does the numbers that are about 20 percent equate to about 4,000 samples each year that were not progressed?” Hedge asked.

“Yes, that is what the data indicates,” replied Professor Wilson-Wilde.

“Does the data show the effect of these thresholds over this period, compared to what was not tested?” Hedge asked.


Samples below the threshold were labeled “DIFP” and other samples where no DNA was detected were also not developed further.


Total samples

Not progressed



18.8 per cent



26.9 per cent



23.3 per cent



22.6 per cent


27, 080

20.2 per cent

The study was also told that of the sub-threshold samples that were passed on for testing, the success rate of obtaining a DNA profile was always above 50 percent – and by 2022 as high as 97 percent.

The Commission of Inquiry must deliver a final report by 13 December at the latest.

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