Validation of a novel forensic method

[Audio] Validation of a novel forensic method Analysis of “of the Ver plex blood identification System” Amanda wise Ethical principles in forensic science 1/8/2026 "Good morning. Today, I will walk you through a critical review of a published validation study for a new forensic instrument. We will cover the importance of validation, examine a specific case study, analyze the tests performed, and evaluate the thoroughness of the study.".

[Audio] Ensure: For Scientific Evidence that Method/Instrument is Fit-for-Purpose in Forensic Application Reproducibility (operator, time, instrument). Accuracy & Precision (under specified conditions). Robustness (varied sample types and conditions) Supports Accreditations (e.g. ISO/IEC 17025) - ensures integrity, admissibility, reliability of evidences in court "Before any method or instrument touches an evidence sample, it must be validated. This isn't just a best practice; it's a cornerstone of forensic quality management. Validation provides the documented, scientific proof that the method works as intended—that it is reproducible, reliable, and versatile. This process is mandated by international accreditation standards like ISO 17025 and is critical for ensuring our results can withstand scrutiny in a court of law.".

[Audio] Title: The VeriPlex™ Blood ID System: What is it? Problem: Catalytic tests for blood (e.g., Kastle-Meyer) lack human specificity, and can be falsely reactive. Solution: The Veri Plex™ System - rapid, immunochromatographic assay. Steps: Extract antigen from stain. Include antibodies to human hemoglobin. Yield visible result on test strip (like a pregnancy test). "The study validates the VeriPlex™ Blood Identification System. Traditional presumptive tests for blood, like the Kastle-Meyer test, react with any peroxidase, including those from plants or chemicals, leading to false positives. VeriPlex aims to solve this by targeting human hemoglobin specifically. It's a simple, lateral flow device that provides a 'yes/no' answer for the presence of human blood, promising greater specificity and speed.".

[Audio] The validation framework: What was tested? Study followed a structured approach based on scientific working group on DNA Analysis methods guidelines. Key validation Parametres Tested: Sensitivity/ Dynamic Range: Minimum sample quantity and detection limits. Specificity: cross- reactivity with non-human blood, common interferents, and other body fluids. Reproducibility & Precision: Consistency across multiple operators, lots, and instruments Robustness: Performance under varied conditions (temperature, humidity). Case-type samples: performance on realistic, aged and compromised samples "The authors structured their validation using established forensic guidelines. They systematically investigated critical parameters. Sensitivity asks, 'How little blood can we detect?' Specificity asks, 'Does it react only with human blood?' Reproducibility ensures.

[Audio] core performance sensitivity & Specificity Efectively Identifies human blood dilution down To 1:100,000 Only a 0.5mm diameter stain needed (very small sample). 0.5mm Why its important: Establishes limits of detection of trace evidence. Specificity findings: No cross-reactivity with animal bloods(dog,cat,horse,cow,pig,deer) No reaction with saliva, semen, urine or common interferents (rust, coffee, bleach) Why its important: targets weakness of presumptive tests; very low false postives "The results here were strong. The system showed exceptional sensitivity, detecting extremely diluted blood, which is crucial for analyzing minute or washed stains. More importantly, its specificity was excellent. It did not react with any of the tested animal bloods or other body fluids. This is the key advantage—it dramatically reduces the risk of a false positive from non-human sources, a major quality improvement over older methods.".

[Audio] Reproducibility & Robustness Reproducibility: 100% concordance across three different instrument lots*. 100% concordance across multiple operators*. Importance: Demonstrates method is operator-independent and manufacture is consistent—key for quality control. Robustness: Reliable results across a range of* laboratory temperatures and humidity levels*. Importance: Proves the method is stable under normal lab variations, ensuring reliability day-to-day. "These tests address the 'R' in reliability. The 100% concordance across different manufacturing lots and different scientists is vital. It means the method is rugged and the product quality is controlled. Similarly, performing correctly under normal lab environmental swings shows it won't fail due to minor, uncontrollable conditions. Both are essential for a method to be considered robust and trustworthy in routine casework.".

[Audio] The Real-World Test: Case-Type Samples ​ Samples tested included: * Aged stains (up to one year old). Stains on *various substrates** (denim, carpet, wood, glass). * Environmentally exposed samples (UV light, heat, humidity). * Mixtures (blood with soil, detergent). * Results: System performed reliably on most substrates and aged samples. * Key Finding: Some false negatives occurred on heavily dyed fabrics (e.g., black denim). * Importance: Identifies limitations and boundaries of the method for real-world application "This is where theory meets practice. The method worked well on most surfaces and with aged stains. However, a critical finding emerged: false negatives on heavily dyed fabrics, like black denim. The authors hypothesize dye inhibitors may interfere. This is a crucial piece of information for an analyst. It defines a specific scenario where the method's reliability drops, which must be documented and considered during evidence examination—a perfect example of validation identifying an operational limit.".

[Audio] Analysis: Strengths of the Validation Study 01 ✔ Comprehensive: ALL core SWGDRAM parameters 02 ✔ Ecologically Valid: REAL “case-type” samples, not just clean controls 03 ✔ Openly reported a CRUCIAL limitation (false negatives on dyed fabric) 04 ✔ Followed rules of forensic validation (eg SWGDAM) 05 ✔ Scientifically valid: replicates, multiple operators for precision data "Overall, this is a strong validation study. Its greatest strength is its comprehensive nature—it didn't just test perfect lab samples. By including challenging, realistic samples, it provided a true measure of operational utility. Furthermore, the authors were transparent in reporting the failure with dyed fabrics, which is scientifically honest and more valuable to the end-user than a 'perfect' but unrealistic report.".

[Audio] Analysis: Identified Gaps & Recommendations * ⚠ Gap 1 - Inhibitor Studies: Dye interference was observed but not systematically characterized. No experiments with a range of known dyes with inhibitory properties. * Recommendation: A dedicated study to identify map inhibitory substances - develop “don’t use” or “use cautiously” list * ⚠ Gap 2 - Quantitative Threshold: No studies on what counts as a “faint positive”. Subjective nature of interpreting faint lines may vary. * Recommendation: Define objective criteria (e.g., reader instrument) or have a firm protocol for interpreting weak results * ⚠ Gap 3 - Extended Mixtures: Blood with other mixtures ?(e.g. paints, oils, other bodily fluids mixed with blood) "While thorough, some analytical gaps remain. First, the dye interference was discovered but not deeply investigated. A lab implementing this method would need to know *which specific dyes* are problematic. Second, like many lateral flow tests, faint lines can be subjective. The study didn't address how to standardize this interpretation, which is a potential source of error. Finally, testing could be expanded to even more complex, 'dirty' mixtures to further stress the system.".

[Audio] Conclusion and Implications for the Lab The validation study *proved beyond a doubt** that the Veri Plex system is a robust, specific, and sensitive method for blood identification in human samples It establishes the *gold standard** for how a forensic lab should conduct its own internal validation before the system can be deployed * Take Home Message: It’s an excellent protocol blueprint, but it also shows that sometimes, validation reveals limitations which must be addressed in the lab's SOP. * Final Thoughts: Good validation, as done here, turns a promising new tool into an admissible tool for forensic scientists in court "In conclusion, this published study provides a robust model of method validation. It proves the VeriPlex system's utility while honestly outlining its limits. For a lab adopting this method, this study serves as the essential starting point. However, the lab must now take that information—especially the warning about dyed fabrics—and incorporate it into their own standard operating procedures. This is how the scientific community builds a reliable forensic toolkit, one validated method at a time.".

[Audio] References * Roelofse, M. M., Steers, N. J., Fistonich, M. L., & Bishop, L. A. (2019). Validation of the VeriPlex™ Blood Identification System for the forensic identification of human blood. *Forensic Science International: Genetics Supplement Series*, 7(1), 845-847. [Link or DOI would be included] * Scientific Working Group on DNA Analysis Methods (SWGDAM). (2016). *Validation Guidelines for DNA Analysis Methods*. * ISO/IEC 17025:2017. *General requirements for the competence of testing and calibration laboratories*. "Thank you for your attention. Are there any questions?".