A scientist became concerned about contamination at Queensland's forensic lab after a high number of bone and teeth samples failed to yield proper DNA profiles, an inquiry has heard.
Angelina Keller, a scientist specialising in cold cases, told the Commission of Inquiry into Forensic DNA testing in Queensland she noticed the problem after changes to the way bone crushing equipment was cleaned at the lab.
The inquiry before Walter Sofronoff KC has been probing a decision not to process crime scene samples that contained extremely small amounts of DNA.
Samples taken from the inside of bones and teeth should only contain DNA from one person, the inquiry heard.
But in November 2020, Ms Keller started getting mixed DNA profiles from bones and teeth.
"I thought it was very unusual. It's the first time I can really remember that happening," Ms Keller told the inquiry.
"Since then, it's happened more frequently, and now I'm at the point that we've got a problem, and we've got to find out what's going on."
Concern 'rusty' equipment contains foreign DNA
In July 2019, the laboratory changed the protocols for cleaning bone processing equipment, the inquiry heard.
Previously, chisels, hammers and saws were scrubbed by hand in a tub containing water and Tergazyme, a detergent that breaks down DNA.
"You could really get in there and scrub everything very well. And you knew it was as clean as you could possibly get it," Ms Keller said.
Under the new regime, bone crushing equipment was cleaned in a dishwasher.
Instead of Tergazyme, scientists were to use bleach or ethanol and Trigen, which is a disinfectant.
In May this year, Ms Keller noticed the chisels used for bone sampling had developed rust due to the new cleaning process.
"When pieces of equipment go rusty, they can be more difficult to clean and more likely to contain foreign DNA," Ms Keller said.
She said the rust could be retaining DNA and contributing to the contamination of bone and teeth samples.
No consultation on changes to bone cleaning
The inquiry heard the new process was brought in by Allan McNevin, who was put in charge of bone testing in 2019.
"What's his scholarship in bone work?" Mr Sofronoff asked.
"When Allan was first put in charge of bones, I don't believe he had any experience in bones or teeth," Ms Keller said.
"Had Mr McNevin to your knowledge scrubbed any instruments clean in his work?" Mr Sofronoff asked.
"I don't know. Not that I'm aware of," Ms Keller replied.
Ms Keller said the change was implemented without testing or consultation with the scientists in the bone unit.
"To be honest, when it's such an important process [of cleaning bone sampling tools] – we don't do it that often – but it is a really important thing that we do, we should do it properly," she said.
"Was it your view there should have been a validation before any change in process?" Counsel Assisting Susan Hedge asked.
"At least a verification or testing. We're going to make this change for this equipment, does it clean it adequately?" Ms Keller said.
Ms Keller also gave evidence about a new extraction method the lab had adopted.
The inquiry heard in April 2018, the lab switched from an "organic" extraction method — a manual process requiring a high level of skill — to one involving a robotic instrument.
Ms Keller said she raised concerns with management and that she has since noticed an increase in the number of low level or no DNA profiles from bones and teeth.
"Coronial bones tend to have lower levels of DNA. We're dealing with compromised bone samples," she said.
"It's harder to get a full profile."
The inquiry continues.
