by Anna Bennett, Science Writer, Promega Corporation
Quality assurance (QA) is an integral aspect of forensic DNA testing as it ensures accuracy, reproducibility, sensitivity and reliability in the results obtained from analyzing DNA. Rigorous standards set by entities such as the Federal Bureau of Investigation (FBI) or the European Network of Forensic Science Institutes (ENFSI) must be met to ensure a level of trust in forensic data. Here, we define quality assurance standards and validation procedures and provide an example of a tool designed to support forensic labs in meeting quality assurance requirements.
DNA extraction, amplification, analysis and STR profiling all take place within the forensic lab and must conform to quality standards. The production of precise and reliable DNA analyses begins with lab equipment that has been validated for compliance with all the appropriate quality controls. Instrument validation and quality control measures ensure that a forensic lab’s procedures are in keeping with the most up-to-date methods and technologies in order to maintain the scientific validity of their analyses over time. These efforts provide DNA analysts greater confidence in the data informing their analyses and that their findings are acceptable evidence.
To meet the stringent FBI QAS, a DNA analysis system in a forensic lab would need to demonstrate the following:
- Instrument Validation and Quality Control: Validation involves a comprehensive assessment to ensure that a DNA analysis system consistently produces accurate and dependable results that are admissible in a court of law. It includes testing the system with known samples to confirm its reliability. Quality control measures should be in place to monitor and maintain the system's performance. These include routine checks, calibration and regular maintenance to detect and rectify any deviations from established standards.
- Data Accuracy and Precision: The production of accurate and consistent DNA profiles is crucial to maintaining a forensic lab’s credibility. The system should generate results with minimal variation between tests and different analysts. Data interpretation, allele calling and peak sizing should be reliable and reproducible to minimize errors and ensure consistency in results.
- Documentation: Comprehensive documentation is essential for transparency and traceability. It should cover all aspects of the system's processes, protocols, validations and quality control measures. Detailed records facilitate auditing and provide evidence of compliance with established standards and procedures.
- Proficiency Testing: Participation in proficiency testing programs is a critical element in quality assurance. These programs involve analyzing blind samples provided by external agencies to assess the accuracy and performance of the system. Proficiency testing helps ensure that the DNA analysis system consistently produces reliable results and is on par with other accredited laboratories.
- Training and Competency: Personnel operating the DNA analysis system should receive comprehensive training to ensure they are proficient in using the technology and interpreting results accurately. Demonstrated competency is necessary to minimize errors and maintain the quality and reliability of the analysis.
- Chain of Custody: Maintaining the chain of custody for DNA samples preserves their integrity and admissibility as evidence in legal proceedings. The system should have well-defined protocols for handling, documenting and securing samples from the moment they are collected to their final analysis, ensuring they are not contaminated or tampered with.
- Reporting: Proper legal and investigative procedures require clear, accurate, and comprehensive reporting of DNA analysis. Reports should include detailed information on the methodology used, results and any relevant statistical data, making them suitable for courtroom presentation and supporting investigative efforts.
By adhering to these quality assurance requirements, forensic DNA analysis laboratories can maintain the highest standards of accuracy, reliability and integrity in their work.
You can read about a capillary electrophoresis instrument proven to meet QA standards set by the FBI in this white paper. The study includes baseline noise and threshold evaluation, precision, resolution, accuracy, reproducibility, sensitivity, signal variability, dye balance, spectral artifact analysis, contamination assessment, mixture samples, and direct amplification. The results of the study demonstrate the capabilities of the instrument, its suitability for use in a forensic casework or database laboratory and detail the level of rigorous testing necessary to ensure production of reliable forensic DNA tools.