![]() Between examiners within the same laboratory (intra-laboratory variability), where protocols and training were expected to be similar and variation was expected to be low.The researchers created new ways to measure the variability in interpretations of DNA mixtures: Then, to objectively assess the variation in forensic DNA interpretation, they created new statistics to quantify interpretation variability. First, they evaluated the current state of the practice in interpretation of DNA mixtures. NIJ-funded researchers from the Defense Forensic Science Center sought to improve mixed DNA analysis, eager to understand the amount of interpretation variation that exists in the analysis of complex DNA samples, both within and between laboratories. Role of software and computational programs. Use of qualitative versus quantitative methods. Imbalanced contributor ratios (which can mask some results). Overlapping alleles between samples (due to multiple contributors). Stutter (from the amplification of short tandem repeats in DNA). Allelic dropout (from the DNA amplification process). Lack of consensus regarding standard methods and protocols. Box 1: Factors contributing to interpretation variability. The 2016 President’s Council of Advisors on Science and Technology (PCAST) called on researchers to “develop methods with enough standardized and quantifiable detail that they can be performed by either an automated system or human examiners exercising little or no judgement.” And more recently, researchers from the National Institute of Standards and Technology (NIST) have reiterated that these problems continue to plague DNA mixture analysis. Current DNA technology is sensitive enough to analyze DNA samples that include contributions from more than one individual, or so called “DNA mixtures.”ĭNA mixtures have, however, proven difficult to interpret due to variation in methods, sample quality issues, and interpretation problems ( Box 1). Objects such as steering wheels, doorknobs, guns, and even clothing often yield “touch DNA” evidence. Now, with highly sensitive techniques, DNA can be picked up from just a few cells left behind. In the not-so-distant past, we needed a fair amount of either blood or semen to create DNA profiles. The genetic code that is found in nearly all cells of the human body can be collected from people’s skin, blood, saliva, and bone to create a profile (or “genetic fingerprint”) to identify, or eliminate, potential suspects in a forensic investigation.ĭNA technology has come a long way. ![]() Research for the Real World: NIJ Seminar SeriesĮxcept for identical twins, no two people have the same DNA.Strategic Challenges and Research Agenda. ![]()
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