Comparing two commercial domestic dog (Canis familiaris) STR genotyping kits for forensic identity calculations in a mixed‐breed dog population sample

Abstract

Almost half of all US households own a dog (Canis familiaris). Though these household pets can attack humans and other animals, they are also frequently victims of cruelty, neglect and theft. In human-oriented investigations, the tendency of domestic dogs to leave behind physical traces (such as hair) can serve as valuable links between crime scenes and suspects/victims. This demonstrated utility of canine biological evidence has created demand for genotyping marker sets for canine forensic genetic testing. Through research and casework, short tandem repeat (STR) panels have been shown to be very efficient for identity and parentage testing in dogs. However, there is an absence of comparative studies between different canine forensic identification kits. The Thermo Fisher Scientific Canine Genotypes TM Panel 1.1 and 2.1 Kits were originally designed and developed for routine and forensic use respectively, although both kits can be used for either purpose. In this study, we evaluated both STR panels to determine how critical forensic genetic metrics are affected by panel-to-panel variation in marker composition and design. Our results show that although STR panel composition can influence estimates such as inbreeding, combined power of discrimination and combined probability of exclusion, greater average allele number values exhibited across all markers in Panel 2.1 facilitated significantly more precise estimates of random match probability (RMP) and combined probability of identity. Furthermore, we demonstrate that a theta (h) correction of 0.09 can be used to conservatively adjust RMPs generated from a small reference database of fewer than 50 samples, confirming that Panel 2.1 is a more robust forensic genotyping system than is Panel 1.1. for domestic dogs. We also demonstrate that opportunistic local sampling of fewer than 50 mixed-breed dogs can produce sufficient discriminatory and exclusionary power with either genotyping kit.

Humans Are Animals, Too: Critical Commonalities and Differences Between Human and Wildlife Forensic Genetics

“…While STR markers have been developed on thousands of nonhuman species for research, there are likely only dozens of taxa for which these markers have been validated and analyzed for forensic purposes . A few domesticated taxa have had core loci proposed ; among those, only horses ( Equus caballus ), cows ( Bos taurus ), and dogs ( Canis lupus familiaris ) have commercial kits available (StockMarks™ Canine, Bovine, and Equine Kits; Canine ISAG STR Parentage Kit; Canine Genotypes Panel 1.1 and 2.1; and Bovine Genotypes Panel 1.2 Kits; Thermo Fisher Scientific, Waltham, MA). None of these kits provide allelic ladders, relying instead on interlaboratory sample sharing or International Society for Animal Genetics comparison testing when allele calls need to be compared between laboratories .…”

Towards Forensic DNA Phenotyping for Predicting Visible Traits in Dogs

“…DNA fingerprinting methods provide strong evidence for individual identification of the involved dog(s). Accordingly, a number of approaches have been published using canine STR loci for dog individualization from crime scene evidence [60][61][62][63][64][65][66][67][68] and guidelines have been established for forensic validation requirement [69,70]. STR profiling allows to answer questions such as: "was this dog the perpetrator of the attack?"…”

The assessment of the efficacy of STRs panels recommended by the ISAG for canine pedigrees analysis for forensic casework

“…For this calculation a random match probability -RMP is used, which shows frequency of observed DNA profile based on actual population data (Kochler et al, 1995;Forrester et al, 2018;Giacalone et al, 2018;Kanthaswamy et al, 2018). The value of RMP and the use of the kit for forensic investigations greatly depends on the number of used STR markers (DeNise et al, 2004).…”