Quantifying DNA loss in laboratory-created latent prints due to fingerprint processing.

Fingerprints, which are associated with touch samples, typically contain a limited amount of DNA. The amount of available DNA can be further reduced when the same touch samples undergo fingerprint processing [1]. The fingerprint development process consists of high-powered lighting (inherent luminescence and UV light) and chemical compounds (ninhydrin, black powder, cyanoacrylate, and rhodamine 6 G) which could reduce DNA quality and quantity. Therefore, forensic scientists often must select one type of analysis over the other due to the destructive nature of processing. DNA and latent fingerprinting are both useful sources for identification, although both can produce partial results. A partial DNA profile may only contain a few alleles, limiting the ability to identify a potential suspect to perform comparisons. A partial fingerprint generally means that only a very small part of the fingerprint is present, which makes comparisons difficult. Because partial results are common, combining data from both fingerprinting and DNA analysis would increase the confidence of an identification of a person. Significant research has been performed to determine if a DNA profile can be obtained from latent processed fingerprints; however, there has yet to be research done in a standardized manner. In this study, we used standardized mock "fingerprints" in order to reduce fingerprint DNA variability and specifically focused on DNA quantitation after each step in the fingerprinting process. Results suggest that latent print processing techniques used on non-porous surfaces (plastic, duct-tape, metal, and rubber) do not affect DNA quantity or quality. In contrast, ninhydrin, a chemical used for processing fingerprints present on porous surfaces (wood and paper), significantly reduced DNA recovery. Together these results suggest that DNA can still be performed on latent print processed items, unless ninhydrin has been used.

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. Supplemental data for this article is available online at https://doi.org/10.1080/20961790.2021.1963088 .

The genetic structure of native Americans in North America based on the Globalfiler® STRs.

Current forensic STR databases, such as CODIS, lack population genetic data on Native American populations. Information from a geographically diverse array of tribes is necessary to provide improved statistical estimates of the strength of associations with DNA evidence. The Globalfiler® STR markers were used to characterize the genetic structure of ten tribal populations from seven geographic regions in North America, including those not presently represented in forensic databases. Samples from the Arctic region, Baja California, California/Great Basin, the Southeast, Mexico, the Midwest, and the Southwest were analyzed for allele frequencies, observed and expected heterozygosities, and F-statistics. The tribal samples exhibited an FST or θ value above the conservative 0.03 estimate recommended by the National Research Council (NRC) for calculating random match probabilities among Native Americans. The greater differentiation among tribal populations computed here (θ=0.04) warrants the inclusion of additional regional Native American samples into STR databases.

Native American population data based on the Globalfiler(®) autosomal STR loci.

Native American population data are limited and thus impact computing accurate statistical parameters for forensic investigations. Thus, additional information should be generated from geographically representative tribes in North America, particularly from those that are not included in existing population databases for forensic use. The Globafiler(®) PCR Amplification kit was used to produce STR genotypic data for 533 individuals who represent 31 Native American tribal populations derived from eight geographically diverse regions in North America. Population genetic estimates from 21 autosomal STRs are reported.