Quality Assurance, Quality Control, and Legal/Reporting Requirements
Quality system
Accreditation to ISO/IEC 17025 and adherence to FBI QAS and SWGDAM standards require document control, validated methods, calibrated instruments, and trained, competency-tested analysts. Internal validation establishes sensitivity, precision, reproducibility, mixture detection, and contamination limits before a method is used on casework. Reagent blanks, negative controls, positive controls, and instrument blanks monitor contamination and performance. Proficiency testing and audits provide external and internal oversight; failures trigger corrective action.
Casework controls
Each batch should include a positive control, a negative amplification control, and a reagent blank. If a negative control shows a peak above the laboratory threshold, the batch is compromised: stop, investigate, document, and re-extract or re-amplify. Traps: a failed control invalidates the affected batch, not necessarily the entire laboratory; a contamination event requires root-cause analysis; controls must be processed through the same extraction and amplification pathway.
Reporting and legal
Reports should state the specimens tested, methods, results, interpretation, limitations, and statistical approach. Use included, excluded, or inconclusive, not match. Chain of custody, evidence consumption, and data retention must be documented. Admissibility follows Frye or Daubert depending on jurisdiction; analysts must explain validation, error rates, and assumptions in plain language. Never overstate a mixture result.
Worked rule
If the reagent blank shows a 70 RFU peak at one locus but the sample profile is strong and the blank is below the analytical threshold, document and review; if the blank exceeds the threshold and shares alleles with the sample, do not report until the source is resolved.