Is the Failure to Disclose the Limitations of Forensic Testing Giving Rise to Misleading Evidence?
Understanding Presumptive Blood Tests
Have you ever seen the following in a forensic statement or report?
“A presumptive test for the presence of blood was positive”
“Apparent blood was detected”?
This means only a presumptive or screening test has been performed, which generated a positive reaction. More often than not, there is no further information about these tests included in the report.
These statements do not mean that blood has been detected.
These tests typically exploit the oxidative capability of blood. However, this process occurs in many other areas of life and is not specific to blood.
How Do These Tests Work?
For the scientifically minded, it looks like this:
[O] + AH2 ------> A + H2O
(catalyst)
This is known as a catalytic reaction, as it relies on a catalyst to speed up the reaction and generally results in a colour change or, in the case of luminol, light. In relation to blood testing, this catalyst is heam, which is contained within the haemoglobin of red blood cells. You may have seen this through the use of Hemastix, Kastle-Mayer test, or ortho-tolidine.
Limitations of Blood Testing
When it comes to these blood tests, they will also react to other substances, including but not limited to:
- Rust
- Red dirt, which contains iron oxide
- Some plant materials
- Oxidising cleaning agents
What this Result Actually Mean?
Unless there is a confirmatory test for the presence of blood, caution should be applied to the preliminary blood test result.
Furthermore, additional caution needs to be applied when it comes to the DNA results. It may not be appropriate to assume any DNA profile detected has been derived from blood.
As lawyers, it is not appropriate to assume a biological fluid has been detected based on these presumptive tests.
It is imperative to find out the limitations of this testing to prevent misleading evidence from being presented in your matter.
Presenting the Limitations of This Evidence in Court
The limitations of these tests are frequently absent from forensic reports and statements. Their absence can allow undue weight to be applied to the testing.
It is imperative to reveal these limitations to the court to prevent evidence overestimation. IFS stands ready to help pinpoint these limitations, ensuring your case evidence receives fair and impartial evaluation.
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.