What is an Independent Forensic Review, and Why Defence Lawyers Need One

When the Science Needs a Second Opinion

Forensic evidence can appear definitive — especially when it comes in the form of a laboratory report from a State forensic service provider. Published studies have indicated that juries and judges perceive reports from State Services providers as highly reliable, even when the content contained in the report is unreliable or incorrect.

But as every experienced criminal lawyer knows, how that evidence was interpreted can be just as important as what was found. It is important that this evidence is interpreted without biasing instruction such as “find POI DNA on…” or “find DNA to determine the handler of the item”. This is where an independent forensic review becomes crucial.

Independent review provides the defence with a clear, unbiased, and scientifically sound understanding of the forensic evidence — helping ensure your client’s case is assessed on the full facts, not the Prosecution’s version of the evidence.

What Is an Independent Forensic Review?

An independent forensic review is a comprehensive, expert analysis of the forensic work conducted in a case — performed by a specialist who is not affiliated with the original laboratory or law enforcement. It involves:

1. Reviewing the case file, laboratory notes, and DNA interpretation data
2. Independently evaluating the scientific validity of methods used (e.g., STRmix interpretation, contamination controls, examination and sampling strategy)
3. Assessing whether results were appropriately interpreted and reported
4. Identifying errors, limitations, or alternative explanations that may not have been fully explored in the prosecution report

In short, it’s an independent quality assurance step — one that can be pivotal in serious criminal cases.

Why Defence Lawyers Need It

Even the best forensic laboratories are not immune to error. Interpretations can be influenced by:

• Complex mixtures or degraded samples
• Analytical thresholds and stochastic effects
• Transfer and persistence of trace DNA
• Number and state of spermatozoa observed
• Inadequate documentation or oversight
• Human bias and / or police instruction, particularly in high-profile or expectation-driven cases

An independent review gives defence lawyers:

Clarity – Understand exactly what the DNA evidence can (and can’t) say.

Confidence – Cross-examine expert witnesses, disclosing limitations and gaining necessary concessions as to what the evidence does and does not mean.

Credibility – Present an impartial, scientifically grounded alternative opinion to the court.

It ensures that every conclusion presented to the trier of fact is transparent, testable, and balanced.

Independent Review in Practice

Recent reviews have uncovered issues such as:

1. Overstated likelihood ratios in probabilistic software outputs
2. Misinterpretation of trace DNA as direct contact evidence
3. Contamination / transfer risks not adequately reported or disclosed
4. Incomplete consideration of alternative propositions

In several cases, these findings have altered the course of proceedings — from charge withdrawal to reduced evidentiary weight in court.

When to Engage an Independent Expert

You should consider requesting an independent review when:

• The prosecution relies heavily on complex or mixed DNA evidence
• Your client has strong instructions in relation to their involvement or there appear to be inconsistencies in the evidence and versions of events
• The likelihood ratios reported are low level, seem inconsistent or unclear
• The limitations to any biological testing are not disclosed
• You don’t have a complete picture of the biological evidence in sexual assault matters — for example, basic statements such as “semen detected” without any disclosure in relation to the testing performed on the number of spermatozoa observed
• There is trace DNA evidence and no guidance in relation to the persistence or transfer of this DNA

Engaging early ensures there’s time to obtain the necessary material — such as case files and examination records — before court deadlines.

In the Words of Defence Counsel
“I want to extend my thanks on behalf of the defence legal team and the accused (and his family) for all your efforts. I am pleased to advise your report assisted in the Prosecution discontinuing the case against our client. I am very grateful for all your efforts and look forward to working together in the future.”
— Hassan Hamka, Solicitor, NSW

Further Reading

• ANZPAA NIFS — Principles for Reporting Forensic Biology Evidence (PDF)
• ISO/IEC 17025 — Testing and Calibration Laboratories
• NATA — Forensic Science ISO/IEC 17025 Appendix (PDF)
• NIST — Evaluation of Forensic DNA Mixture Evidence: Guidelines for Evaluation, Interpretation and Reporting
• SWGDAM — Interpretation/Validation Guidelines (PDF)