Top 5 Tips: Preparing to Cross-Examine an Expert Witness (Part 1)
DNA is very persuasive to juries. It is often erroneously considered an absolute science, from juries, lawyers and even judges.
But DNA evidence is easily misunderstood, often has undue weight placed on it, and often comes with undisclosed limitations.
It is imperative lawyers understand these limitations and are prepared to cross-examine an expert witness in such a way that they become clear to the jury—or at the minimum, know when to challenge or even throw out evidence.
As an expert witness with hundreds of court cases under my belt, I have compiled my top 5 tips to help lawyers prepare for cross-examination. In part 2, I will detail my top tips on handling a cross-examination.
1. Don’t Rely on the Statement/Certificate to Give You the Full Picture
Often, pertinent information such as the types of tests performed is contained in the examination notes or case files. It is important to know what the evidence is, what tests have been performed, and what the results mean.
2. Do Not Make Assumptions About the Origin of the DNA
Has a test for the presence of a biological fluid been performed? If so, it is important to know the limitations of the biological fluid testing, as sometimes these limitations are not disclosed in the reports/statements. Not knowing the limitations of these tests may lead to the evidence being misrepresented. For example, tests for the presence of saliva can also react with sweat, urine, and breast milk.
3. Large Numbers in the Report Do Not Always Equal Probative Value
It is possible for juries to be swayed by large numbers that actually do not have evidentiary value. If there is not a clear link, you should consider an application to have the DNA evidence excluded.
4. Just Because the Laboratory Is Accredited, Do Not Assume Mistakes Have Not Been Made
Accreditation only assures the high-level functioning of a laboratory; it does not assess the effectiveness of the laboratory’s practices. DNA analysis is still completed by humans, and there are multiple instances of reputable labs making simple errors or using less-than-effective methods (Queensland DNA Inquiry). Engaging an independent expert witness can identify these mistakes or failures in procedure and prevent them from reaching the courtroom.
5. If You Are Instructing an Independent Expert, Do It as Soon as You Can
Obtaining material required, conducting a review, and briefing and equipping the lawyer to deal with the evidence in court takes a lot of time and expertise. The more time an independent expert has, the stronger your case will be.
DNA Expert Witness Testimony
We’re passionate about ensuring forensic biology and DNA evidence is presented to the courts in an impartial, yet comprehensive manner, and that potentially misleading evidence isn’t relied upon. We also want our clients to understand the strengths and limitations of forensic evidence in their cases.
Independent
As an independent forensic service provider, we offer unbiased and impartial analysis. Our independence guarantees that our findings are based solely on scientific evidence, free from external influences. This objectivity is crucial in ensuring the credibility and reliability of our forensic reports.
Confidential
We understand the sensitive nature of forensic investigations. Confidentiality is a cornerstone of our services. We handle all cases with the highest level of discretion, ensuring that your privacy and the integrity of the investigation are maintained at all times.
Trusted
Integrity is at the heart of everything we do. We are committed to ethical practices and uphold the highest standards of honesty and transparency in all our investigations. You can trust that our findings are accurate, thoroughly vetted, and presented with complete integrity.
Professional
Our team adheres to the highest standards in forensic science, ensuring that every case is handled with the utmost care and precision. We strive for excellence in all our services, providing reliable and accurate forensic analysis.
Highly Experienced
Our team comprises forensic experts with extensive experience across various forensic disciplines. With years of practical experience and advanced training, our professionals bring a wealth of knowledge to each investigation. This expertise ensures that we deliver top-tier forensic solutions tailored to your specific needs.
Approachable
We work closely with you, offering guidance and support throughout the investigation, ensuring you feel confident and informed. Our team is approachable and dedicated to making the forensic process understandable and straightforward.
Get Started
Choosing Independent Forensic Services means partnering with a team that values professionalism, experience, approachability, independence, confidentiality, and integrity. Trust us to provide the forensic expertise you need to achieve justice.
How We Can Help You
With Independent Forensic Services, you gain access to a team of experts.
An Expert Team Lead by Jae Gerhard
Jae Gerhard is a Forensic DNA Expert and the Principal Forensic Scientist at Independent Forensic Services, bringing over two decades of frontline experience in forensic biology. She has worked on some of Australia’s most complex and high‑profile cases with the Australian Federal Police and New South Wales Police, as well as international disaster victim identification operations in Bali and Thailand.
Specialising in DNA analysis, STRmix™, biological fluid examination, and bloodstain pattern interpretation, Jae now works independently with criminal defence teams to review and challenge forensic evidence. Her mission is simple: to ensure the science presented in court is accurate, balanced, and truly understood.