By Karl Hoerr -
It’s been a vital tool in solving crimes for many years, but in some cases DNA evidence has resulted in wrongful convictions. Its ability to answer ‘who’ a DNA profile belongs to is widely accepted, less so ‘how’ the profile got wherever it was found. A new method of scientific reporting provides a framework for the data but remains controversial and is yet to be adduced at a trial in Australia. A leading scientist in the field says the mere existence of this method changes how experts will be able to give evidence.
Helen Roebuck is a forensic scientist in the field of DNA and biological fluid evidence and is the Principal Scientist at Roebuck Forensics. She’s due to address the Legal Aid NSW Criminal Law Conference in June.
Speaking to LSJ ahead of the event, Roebuck explains that since the early 2000s, when science realised that DNA could be transferred via an intermediary surface, an occurrence known as ‘DNA transfer’, our courts have heard scientists ruminate over how the DNA might have got there.
“And that concept of more or less likely, we find aligns itself well to the legal language, but scientifically, it’s very speculative. And that speculative way of evaluating … DNA transfer evidence has contributed worldwide to wrongful convictions, including the wrongful conviction of Fitzgerald in South Australia,” she says.
Fitzgerald v The Queen
Roebuck is referring to the High Court’s 2014 acquittal of Daniel Glenn Fitzgerald, who was convicted of murdering another man and seriously assaulting a second, at a home in Adelaide in 2011. The prosecution case was that Fitzgerald was part of a group that forced its way into the home, planning to cause grievous bodily harm to people inside. The case against Fitzgerald relied on DNA evidence found on a didgeridoo at the crime scene.
Fitzgerald’s lawyers had argued theories consistent with his innocence were open on the evidence, including that his DNA was transferred to the didgeridoo because Fitzgerald had shaken hands with one of the men who was present at the crime scene, at a boxing match the night before the attack.
The High Court found the contention that Fitzgerald’s DNA in the sample obtained from the didgeridoo derived from his blood, was not made out beyond reasonable doubt. It also found the recovery of the DNA did not raise any inference about when and in what circumstances it was deposited there.
Roebuck says experts have often adopted a casual application of scientific data in Australian courts, with qualifiers such as ‘in their opinion’ and ‘based on data that’s available to them’.
“And that ad hoc use of data, whilst (it) is a step forward, still has its own issues because whilst it provides some verbal weight, there isn’t really a formal evaluation of the evidence in light of that data,” she says.
Activity Level Reporting
Roebuck says there’s now a scientifically acknowledged approach to evaluating how DNA came to be on an item. It’s known as ‘Activity Level Reporting’ and has been recognised by scientific bodies internationally and in Australia.
“It gives the scientist a framework in which they can compile the most relevant data that is applicable to the question and apply it in context of the matter in evidence,” she says.
“And what that might produce is a statistic or a likelihood ratio that may be presented something like, ‘It’s 20 times more likely that the accused has handled the knife.’”
Roebuck says many government laboratory scientists have undertaken training in this area, but such a report is yet to be accepted into evidence, although there have been attempts.
She says regardless, it has an impact on how DNA evidence should be presented in court.
“[T]he critical point in 2025 is that this type of evaluation should now either be conducted to give the court a formal, scientific, robust opinion on the evidence, or the DNA expert should really be saying very little if anything about how the DNA got there.”
Why is it controversial?
In criminal law, the burden of proof sits entirely with the Crown, but the method described here would see alternative theories being proffered.
“This type of evaluation does require (the) defence to provide a version of events, which clearly in an adversarial system, is not required,” says Roebuck.
She also concedes that the high cost of providing such services is a problem. “[T]he labs that are carrying out this work would quote around eight weeks to produce one of these reports,” she says. “They are very resource intensive.”
Roebuck also says the method has limitations that don’t exist with identification evidence. “We can take a controlled DNA sample and process it through the system and show that that system gives the correct answer,” she says.
“The problem with this evaluative reporting is there is no known correct answer. It’s an evaluation of the evidence. It’s a truly subjective opinion on the evidence.”
Roebuck says it’s important for lawyers to be across the developments in this field. “From the perspective of the defence lawyer, I think I would advise them to be cautious with the questions around how the DNA came to be there and to familiarise themselves with the concept of activity level reporting before advancing to trial, simply so that they can challenge answers that are provided by the expert on the stand.”
On the question of whether to engage an expert in the field, she says that depends on the nature of the case. “If the DNA carries significant weight in your matter, the best thing to do is to instruct somebody who fully understands the DNA evidence and the guidelines and the reporting methods that have been applied.”
You can learn more about DNA evidence, representing trans clients and more at the Legal Aid Criminal Law Conference, 25-27 June 2025 at the Hyatt Regency Sydney.
Register for the 2025 Criminal Law Conference here.
The keynote speaker is The Honourable Justice Dina Yehia SC.
