But highly sensitive techniques often pick up mixtures of DNA from multiple people, some of whom may have had nothing to do with the crime being investigated. This increased sensitivity makes DNA useful for investigating a greater variety of crimes. Today, they can get a genetic fingerprint from the “touch DNA” that a person leaves behind when handling doorknobs, firearms and other objects. When DNA methods were first developed in the 1980s, labs needed the amount of DNA found in a dime-sized blood or semen stain to produce a genetic fingerprint. Those challenges have increased in recent years with advancing technology. The NIST report only addresses DNA mixtures, which can present much greater challenges. The report also recommends that researchers and forensic laboratories publish this data in a way that will allow results from different studies to be more easily compared.ĭNA profiling generally produces very reliable results when the evidence contains sufficient DNA from a single individual. The report specifies the types of data that would enable an independent assessment and shows how statistical methods could be used to assess performance if that data were available. Forensic laboratories conduct internal studies to test their own systems, but most do not make the resulting data publicly available, partly out of privacy concerns surrounding the genetic data used in those studies. The review identified many peer-reviewed studies of PGS systems, but most did not include the type of detailed data that would allow for an independent assessment of system performance. The report reviewed those systems as well as the larger workflows in which they are used. PGS systems are used to perform complex statistical calculations when interpreting DNA mixtures. The NIST review states that currently “there is not enough publicly available data to enable an external and independent assessment of the degree of reliability of DNA mixture interpretation practices, including the use of probabilistic genotyping software (PGS) systems.” These reviews fill a need identified in a landmark 2009 study by the National Academy of Sciences, which found that many forensic disciplines lack a solid foundation in scientific research. NIST scientific foundation reviews document and evaluate the scientific basis for forensic methods. If any commenters who have already submitted comments wish to provide supplemental or updated comments, we encourage them to do so. All comments received to date will be considered and need not be resubmitted. Eastern Standard Time on November 19, 2021. NIST is re-opening the public comment period on this draft report from Octountil 11:59 p.m.
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