The Development and Validation of a Standardized Canine STR Panel for Use in Forensic Casework (NIJ Grant No. 2004-DN-BX-K007)

The American Pet Products Manufacturers Association 2007-2008 National Pet Owners survey found that 39% of U.S. households have at least one dog (APPMA 07-08A). Given that dogs regularly come into close contact with humans, canine biological material is frequently found at crime scenes and constitues a useful source of evidence. Testimony based on short tandem repeats (STRs) analysis of animal DNA evidence has been used in a number of court cases worldwide. For example, casework based on domesticated dog DNA has been instrumental in successfully linking a perpetrator to a crime scene in instances of murder, burglary, and sexual assault and in cases of animal abuse and theft. Unfortunately, despite its tremendous potential for facilitating forensic investigation, canine DNA remains under-utilized as a source of evidence. The few laboratories that currently perform forensic analysis of canine DNA use a variety of marker sets with little overlap among them. Recent court challenges to canine DNA analysis have demonstrated a need for a standardized canine STR panel that has been validated according to human forensic guidelines. In collaboration with the California Department of Justice, the National Institute of Standards and Technology, the National Institute of Health, the Federal Bureau of Investigation, MMI Genomics, and Finnzymes, we developed and validated a canine forensic fluorescentbased multiplex composed of 18 independently-segregating STR markers that are robust, reliable, and informative for all dog breeds. In addition to STR markers, the panel also includes the gender identification and the canine Zinc Finger gene. This multiplex was used to profile Pit Bull Terrier and Rottweiler samples (two breeds frequently involved in forensic cases); mixedbreed samples, and a collection of pedigreed pure-bred dogs (over 667 unrelated individuals representing over 50 American Kennel Club-recognized breeds). These subpopulations formed the foundation of our canine database. The resulting data was used to assess genetic and geographic substructure and to estimate recombination ratios and inbreeding coefficients, including Fst. In addition, genetic diversity among and within the regional and breed datasets were compared. Each pedigreed dog population was genetically distinct and could be differentiated from the mixed breed dog population. Genetic diversity was slightly clinally distributed among the different U.S. regions. The results herein provide further support for using allele frequency data with the canine STR multiplex to convey the significance of identity testing for forensic casework, parentage testing, and breed assignments. The underlying scientific procedures and results have been submitted to peer-reviewed journals and presented at national and international conferences. This document is a research report submitted to the U.S. Department of Justice. This report has not been published by the Department. Opinions or points of view expressed are those of the author(s) and do not necessarily reflect the official position or policies of the U.S. Department of Justice. 2 Table of