Forensic DNA Analysis Updates and Training | January 2017

The Scientific Working Group on DNA Analysis Methods (SWGDAM) was established in 1988 to bring scientists worldwide to validate forensic DNA methods and establish guidelines for forensic laboratories. Their guidelines became de facto standards recognized by courts as minimum requirements for quality forensic DNA analysis programs. Labs can set themselves apart by going through rigorous accreditation processes, such as through ANSI's National Accreditation Board (ANAB), which audits facilities to ensure methods and work products abide by international standards for forensic testing.

The Technical Working Group on DNA Analysis Methods (TWGDAM) provides guidelines for DNA laboratory operations. Laboratories should follow these guidelines as closely as possible. Guidelines include minimum qualifications and procedures for DNA testing. Laboratories should document contamination outbreaks and their resolution. When contamination occurs, laboratories should contact manufacturers to determine if it was a defective lot. Laboratories should have procedures to be advised when contamination is found.

The MIX 05 study (2005) sent contrived mixtures to 69 laboratories and found wide variation in how laboratories interpreted mixtures, signaling a real problem with standardization. This prompted the ISFG to issue mixture interpretation guidelines in 2006. The National Academy of Sciences report in 2009 was critical of many pattern matching fields but did not address DNA mixture problems. SWIGDAM issued mixture interpretation guidelines in 2010-2011, requiring stochastic thresholds and addressing consistency. Despite these efforts, problems continued to be discovered years later.

DNA interpretation follows guidelines from organizations like SWGDAM (Scientific Working Group on DNA Analysis Methods). Laboratories establish guidelines for inclusionary, exclusionary, and inconclusive results based on their validation data. The numerical range for inconclusive results can vary between laboratories, and some scientists may reasonably disagree with the application of inconclusive ranges when reporting likelihood ratios. Each laboratory sets their procedures which they must follow.

Forensic science has specialized scientific working groups for different types of evidence: (1) SWGIT - Scientific Working Group on Emerging Technology, (2) SWGDA - DNA analysis methods, (3) SWGFAST - Shoe print and tire tread evidence, (4) SWGMAT - Material analysis, (5) SWGDE - Forensic document examination, (6) SWGFRA - Friction ridge analysis, (7) SWGFAST - Firearms and tool marks, (8) SWGD - Digital evidence.

Laboratory safety requires constant vigilance even during busy periods when shortcuts are tempting. Essential safety information includes Safety Data Sheets (SDS) describing substances' ingredients, properties, and hazards, plus facility-specific chemical hygiene plans. Personal Protective Equipment (PPE) must be selected based on specific hazards—eyewear ranges from safety glasses to face shields, lab coats protect against splashes, and gloves match material hazards. Respirators require proper fit testing and training. Footwear must be closed leather with protective toe plates. All PPE must be inspected before use and replaced if damaged. Remove PPE before leaving and wash hands to prevent contamination spread.

This comprehensive section covers the foundational elements of laboratory safety management. A designated laboratory supervisor ensures a safe working environment, presents equipment introductions, and makes workers aware of emergency facilities including showers, eyewash stations, fire extinguishers, and fume hoods. Technical rules for dangerous substances (TRGS) must be accessible in every laboratory, reflecting current scientific knowledge in occupational medicine and hygiene. Personal protective equipment requirements include long trousers and covered shoes with trousers not tucked inside shoes, 100% cotton head protection, and safety glasses instead of contact lenses. Every chemical compound is labeled with danger symbols. Different types of gloves exist for handling chemicals. Eating and storing food in laboratories is absolutely forbidden. When assembling apparatus, improvisation is not welcome; equipment must be well-constructed, stable, and include pressure vents to prevent dangerous pressure surges. High temperatures combined with flammable solvents require reflux condensers. Hot glass appears identical to cold glass and can cause burns; glass is fragile and causes cuts.

Personal protective equipment (PPE) forms the foundation of laboratory safety and consists of three essential components. First, laboratory splash goggles with CAP vents protect against chemical splashes, unlike impact goggles with tiny holes that allow liquids to pass through. Second, gloves serve as the first line of defense against toxic, corrosive chemicals, and contact sensitizers; nitrile gloves offer superior protection compared to latex at approximately double the cost. Third, protective clothing includes 100% cotton long-sleeve shirts (avoiding polyester which melts and reacts with chemicals), full-length pants, closed-toe shoes, and tied-back hair to prevent flame exposure. Together, these PPE elements create a comprehensive barrier between the researcher and potential hazards.

Laboratory safety encompasses three fundamental pillars: personal protective equipment (PPE), proper waste disposal procedures, and emergency response systems. PPE forms the first line of defense, consisting of five essential items: safety goggles made from polycarbonate or PVC to protect against chemical splashes and debris; face masks to filter harmful vapors and dust; laboratory gloves (latex or nitrile) to prevent skin contact with hazardous chemicals and biological specimens; long-sleeved laboratory coats made from cotton or similar materials to shield the body from splashes; and closed-toe safety shoes with rubber soles for foot protection. The correct sequence for donning PPE is: goggles first, followed by face mask, then laboratory coat, gloves, and finally safety shoes. All laboratory personnel must wear complete PPE before entering the laboratory to protect against acids, alkalis, biological agents, and physical hazards.

All laboratories share common safety rules: no smoking or open flames (labs must have sensors), hair must be tied back, appropriate PPE required (lab coat, eye protection, gloves, closed-toe shoes), no eating/drinking to prevent contamination, and chemicals should never be tasted or smelled. Laboratory access must be controlled with clear entry/exit boundaries, personnel must be authorized and trained through orientation, clean and dirty areas must be separated, hand hygiene is critical, lab-specific vaccinations are required, and health changes must be reported to supervisors. The hierarchy of risk control measures consists of four levels: (1) Elimination of hazard - removing the hazard entirely; (2) Engineering controls - containing hazards at their source (fume hoods, sealed containers); (3) Administrative controls - procedures, training, and protocols; (4) Personal protective equipment (PPE) - the last line of defense. Laboratory coats protect against chemical spills and splashes, should be fastened with buttons or Velcro, worn outside the laboratory to prevent contamination, and made of materials resistant to acids, bases, and flammable substances. Proper glove selection depends on specific hazards: chemical concentration, temperature, contact duration, and frequency. Types include latex, vinyl, nitrile, neoprene, reusable nitrile, Nomex/Zex, butyl, and Viton. Respiratory protection includes surgical masks, particulate respirators, chemical cartridge respirators, and powered air-purifying respirators. Proper PPE sequence: put on lab coat first, then respirator mask, safety glasses/goggles, and gloves last. When removing: remove gloves first (contaminated), then glasses/goggles, mask, and lab coat last. Never remove glasses with gloved hands to prevent contamination.

Forensic laboratories implement multiple quality control measures: validated procedures shown to be reliable and reproducible, approved laboratory policies, personal protective equipment, clean work areas to prevent contamination, positive and negative controls to verify system functionality, reagent blanks to detect contamination, technical review by qualified examiners, and administrative review for formatting and accuracy before report release.

Quality is defined as meeting or exceeding established standards, with quality control being the systematic approach to achieving this. Laboratories demonstrate compliance through accreditation bodies (UKAS, NABL) and international standards like ISO 9001. Quality Assurance (QA) is proactive, focusing on processes and procedures before errors occur, while Quality Control (QC) is reactive, addressing specific products and services after production. Four main goals guide forensic laboratories: sample integrity, preservation, accuracy/reliability of results, and reproducibility. Maintaining quality requires four interconnected pillars: staying current with scientific methods, creating clear reports communicable to non-experts, proper equipment maintenance and calibration, and continuous staff training through refresher courses.

Quality Assurance (QA) is a review system conducted by personnel not directly involved in laboratory processes, reviewing quality control activities and correlating errors, complaints, and failures. Quality Control (QC) is a system of routine technical activities ensuring precision and accuracy through quality control reagents run in every measurement series. QC ensures results reflect true analyte values with specified confidence. The three phases of QA are pre-analytical (specimen collection, transport, patient identification), analytical (actual testing, calibration, personnel proficiency), and post-analytical (reporting, interpretation, computer transcription).

Quality Assurance (QA) and Quality Control (QC) are two distinct but related concepts. Quality Assurance is a proactive approach that ensures quality is maintained throughout the entire process, from sample collection to report dispatch. Quality Control is a reactive approach that focuses on testing and verifying results at specific points. QA ensures that the correct procedures are followed, while QC verifies that the results meet the required standards.

Quality Control is designed to identify whether laboratory tests are performing correctly before releasing patient results. It involves checking analyzers and performing verification methods to prevent errors. Quality Assurance is designed to identify patient results before releasing them, improving the quality of reported results. QC is a branch of Quality Assurance, which is part of Total Quality Management. The laboratory work flow includes sample collection, transportation, reception, testing, record keeping, and result reporting.