An inter-laboratory study of DNA-based identity,parentage and species testing in animal forensic genetics

The probative value of animal forensic genetic evidence relies on laboratory accuracy and reliability.Inter-laboratory comparisons allow laboratories to evaluate their performance on specific tests and analyses and to continue to monitor their output.The International Society for Animal Genetics(ISAG)administered animal forensic comparison tests(AFCTs)in 2016 and 2018 to assess the limitations and capabilities of laboratories offering forensic identification,parentage and species determination services.The AFCTs revealed that analyses of low DNA template concentrations(≤300 pg/μL)constitute a significant challenge that has prevented many laboratories from reporting correct identification and parentage results.Moreover,a lack of familiarity with species testing protocols,interpretation guidelines and representative databases prevented over a quarter of the participating laboratories from submitting correct species determination results.Several laboratories showed improvement in their genotyping accuracy over time.However,the use of forensically validated standards,such as a standard forensic short tandem repeat(STR)kit,preferably with an allelic ladder,and stricter guidelines for STR typing,may have prevented some common issues from occurring,such as genotyping inaccuracies,missing data,elevated stutter products and loading errors.The AFCTs underscore the importance of conducting routine forensic comparison tests to allow laboratories to compare results from each other.Laboratories should keep improving their scientific and technical capabilities and continuously evaluate their personnel’s proficiency in critical techniques such as low copy number(LCN)analysis and species testing.Although this is the first time that the ISAG has conducted comparison tests for forensic testing,findings from these AFCTs may serve as the foundation for continuous improvements of the overall quality of animal forensic genetic testing.

Genetic differentiation between and within Northern Native American language groups:an argument for the expansion of the Native American CODIS database

The National Research Council recommends that genetic differentiation among subgroups of ethnic samples be lower than 3%of the total genetic differentiation within the ethnic sample to be used for estimating reliable random match probabilities for forensic use.Native American samples in the United States’Combined DNA Index System(CODIS)database represent four language families:Algonquian,Na-Dene,Eskimo-Aleut,and Salishan.However,a minimum of 27 Native American language families exists in the US,not including language isolates.Our goal was to ascertain whether genetic differences are correlated with language groupings and,if so,whether additional language families would provide a more accurate representation of current genetic diversity among tribal populations.The 21 short tandem repeat(STR)loci included in the Globalfiler^(■)PCR Amplification Kit were used to characterize six indigenous language families,including three of the four represented in the CODIS database(i.e.Algonquian,Na-Dene,and Eskimo-Aleut),and two language isolates(Miwok and Seri)using major population genetic diversity metrics such as F statistics and Bayesian clustering analysis of genotype frequencies.Most of the genetic variation(97%)was found to be within language families instead of among them(3%).In contrast,when only the three of the four language families represented in both the CODIS database and the present study were considered,4%of the genetic variation occurred among the language groups.Bayesian clustering resulted in a maximum posterior probability indicating three genetically distinct groups among the eight language families and isolates:(1)Eskimo,(2)Seri,and(3)all other language groups and isolates,thus confirming genetic subdivision among subgroups of the CODIS Native American database.This genetic structure indicates the need for an increased number of Native American populations based on language affiliation in the CODIS database as well as more robust sample sets for those language families.