DNA Profiling Is Key to Modern Criminal Investigation: Interview with DNA Expert Helen Roebuck

Prior to the widespread roll out and application of DNA testing techniques in law enforcement investigations in the 1990s, police detectives were reliant upon fingerprinting, the analysis of physical evidence and witness testimonies, which unlike DNA evidence, can lead to false assumptions and even convictions.

DNA is the unique chemical code in every person’s cells. DNA profiling is the forensic testing of DNA samples left at the scene of a crime, with the aim of proving who the offender is via the matching of the evidence at the scene with the perpetrator’s DNA.

DNA was identified in the 1950s, while genetic fingerprinting was developed in 1984, and in 1986, law enforcement first applied this method forensically, resulting in a killer in the UK being convicted of a murder that another man had already confessed to.

This first-time application of forensic DNA testing saw Colin Pitchfork identified, via his DNA, as having murdered a 15-year-old girl and he was subsequently convicted.

At the time, the true offender was identified, the other man who had already confessed to the murder was then no longer considered a suspect.

And as DNA profiling went on to be applied to criminal investigations at an increasing rate over the 1990s, stories periodically emerged involving previously wrongly convicted inmates suddenly being acquitted of their crimes due to the accuracy of the DNA testing techniques then being applied.

DNA profiling in NSW

The first DNA database was established in the UK in 1995, and this made the matching of DNA at crime scenes much more efficient when the wrongdoer already had a recorded sample.

Run by the Australian Criminal Intelligence Commission (ACIC), the National Criminal Investigation DNA Database has been in operation since 2001. The NCIDD today contains 1.8 million samples. And the NSW Police Force has had its own DNA profiling system since 2009.

Forensic biologist Helen Roebuck assisted NSW police with the establishment of its DNA profiling system. Roebuck has over 20 years’ jurisdictional experience working in this area and she’s provided assistance, as well as court testimony, in respect of countless indictable matters.

Roebuck Forensics is an Australian forensic science practice, which specialises in DNA expert witness services, primarily in relation to criminal matters.

The Roebuck Forensics Lawyers Portal has become a favourite amongst Australian legal practitioners, as it provides a comprehensive DNA guide for lawyers in respect of how the science relates to criminal proceedings in 2025.

Sydney Criminal Lawyers spoke to Roebuck Forensics principal forensic scientist Helen Roebuck about the development of DNA testing, how the technique is currently applied in criminal investigations, along with the role she plays in the courtroom, when she’s called upon to testify.

DNA testing became widely available to police in the 1990s. It had a reputation for providing accuracy when applied in forensic investigations.

Ms Roebuck, you’ve been working as a forensic biologist for two decades, so how would you say DNA profiling has developed since its inception? And where are we at now with this forensic science?

In the early days, we essentially believed that a person must have touched or deposited fluid at the crime scene to leave their DNA.

We came to learn of course, that a person’s DNA can arrive upon another person or item in a variety of ways and without making direct contact.

This revelation developed alongside a very significant increase in testing sensitivity and further advancements.

We can now obtain a useable DNA profile from just a few cells, meaning crime scene samples are frequently a complex mixture of multiple DNA contributions.

These DNA contributions may be from background DNA that persisted upon the surface, from persons that contacted the surface bearing their own or others DNA, or even from someone speaking or coughing towards the surface.

Today, these concepts are not new to science, however they are challenging within the courtroom because proceedings seek answers as to not just who, but how events took place.

Over the four years commencing in 2009, you helped to develop the NSW Police Force’s own DNA profiling and case reporting system.

Established in 2001, the National Criminal Investigation DNA database (NCIDD) holds more than 1.8 million DNA profiles gathered by police across the country, with samples ranging from those taken at crime scenes, from convicted criminals, suspects and unknown human remains.

So, what sort of role does DNA testing play in police investigations these days? How would you say the advent of this technology has changed law enforcement?

The utilisation of the DNA database has made a publicly visible contribution to many high-profile Australian cold case matters over recent years.

Use of the database is of particular value in a stranger scenario, when the suspect may not have been identified otherwise.

Such scenarios often find the alleged offender without innocuous reason for their DNA deposition.

Whilst important and of public interest, stranger scenarios are statistically infrequent in criminal proceedings.

DNA is most commonly relied upon in circumstances where the parties are known to one another, with New South Wales alone testing over 30,000 samples a year.

Known parties is scientifically and forensically complex because a mere DNA match does not necessarily go substantially towards proving the events, however juries do find DNA evidence highly inculpatory.

Over time, the somewhat overstated reliability of DNA evidence has seen an excess dependence upon DNA in law enforcement and subsequently in criminal proceedings.

Ms Roebuck, you’re a forensic DNA expert, which means that criminal law firms can engage your services as an expert witness to testify in court in regard to DNA evidence.

If DNA evidence is involved in a criminal trial, in what sort of circumstances are your required to appear in court to testify? And does your work ever involve providing the defence with pretrial advice on specific matters that lawyers then apply themselves in the courtroom?

I am frequently required to appear at voir dire hearings and at trial to be cross examined on my expert report.

In certain matters, I may be required to advise counsel in preparation for pretrial or hearings and to comment upon supplementary reports or transcripts.

Whilst I give evidence in many types of matters, sexual assault is proportionately common for a number of reasons, including that the evidence is often complex, with various biological fluids and trace DNA.

Such circumstances where the parties are known to one another present the greatest risk of the court drawing invalid inference as to the alleged activity.

Typically, my involvement starts with an overview of the DNA casefile to verify the likelihood ratios and to compare the lab work against the evidentiary samples collection procedures at the crime scene.

These steps can be discussed with defence to assist with an evaluation as to the weight of the DNA evidence.

Often defence utilise this in consideration as to an application for exclusion, discussion with prosecution or an evaluation as to whether an expert report is the appropriate next step towards challenging the DNA.

And lastly, as mentioned, forensic DNA testing has been increasingly applied since the 1990s and it’s been dramatically developed and refined ever since.

So, how do you see this forensic tool developing into the future? And is it ever going to get to the point where the techniques become so accurate that there will be no room for further refinement?

As a scientist, I could never comprehend a future with no room for refinement or further knowledge.

Over recent years, the scientific community has continued to experiment and produce data.

Current efforts look to evidence a reliable method of statistically weighting the likelihood of how the DNA got there.

This evaluative process is called Activity Level Reporting (ALR). There are complicating factors to this process for the courtroom, including that the lab scientist will invoke a defence version if none is given.

This new and novel process is emerging in Australian evidence and its pathway appears set to be the foreseeable future of DNA in the immediate term.