Investigative genetic genealogy: Current methods, knowledge and practice

Abstract

Investigative genetic genealogy (IGG) has emerged as a new, rapidly growing field of forensic science. We describe the process whereby dense SNP data, commonly comprising more than half a million markers, are employed to infer distant relationships. By distant we refer to degrees of relatedness exceeding that of first cousins. We review how methods of relationship matching and SNP analysis on an enlarged scale are used in a forensic setting to identify a suspect in a criminal investigation or a missing person. There is currently a strong need in forensic genetics not only to understand the underlying models to infer relatedness but also to fully explore the DNA technologies and data used in IGG. This review brings together many of the topics and examines their effectiveness and operational limits, while suggesting future directions for their forensic validation. We further investigated the methods used by the major direct-to-consumer (DTC) genetic ancestry testing companies as well as submitting a questionnaire where providers of forensic genetic genealogy summarized their operation/ services. Although most of the DTC market, and genetic genealogy in general, has undisclosed, proprietary algorithms we review the current knowledge where information has been discussed and published more openly.

Developments in forensic DNA analysis

“…There are ongoing concerns about sharing and privacy of genetic data and the legality of these types of search, as well as the ethics of individuals who have not taken a genetic test being exposed to attention from investigators because a relative has [137,[144][145][146]. There are also no validation studies of genealogical techniques for forensic use [138,139], but the techniques are used only to generate intelligence leads in investigations, often when they have been cold for many years, and any leads would always be verified using standard STR profiling [140]. With the recent acquisition of GEDmatch by forensic genomics company Verogen (https://verogen.com/gedmatch-partners-with-genomics-firm/), along with the launch of a kit specifically designed for genealogical applications (https://verogen.com/products/forenseq-kintelligencekit/), it seems likely that these methods will become commonplace in investigations.…”

Impact of SNP microarray analysis of compromised DNA on kinship classification success in the context of investigative genetic genealogy

“…A more indirect way to find unknown perpetrators via focused police investigation is through investigative leads obtained via the prediction of externally visible characteristics of the unknown stain donor from crime scene DNA, including appearance traits (6), bio-geographic ancestry (7), and chronological age (8), in the context of Forensic DNA Phenotyping (9). Most recently, investigative genetic genealogy (IGG) has started to emerge as new approach to find unknown perpetrators with the help of DNA (4,10). IGG, also known as forensic genetic genealogy (FGG), is based on genomic data from hundreds of thousands of autosomal single nucleotide polymorphisms (SNPs) typically generated with SNP microarray technology (10).…”

“…Most recently, investigative genetic genealogy (IGG) has started to emerge as new approach to find unknown perpetrators with the help of DNA (4,10). IGG, also known as forensic genetic genealogy (FGG), is based on genomic data from hundreds of thousands of autosomal single nucleotide polymorphisms (SNPs) typically generated with SNP microarray technology (10). Because of the large number of autosomal SNPs involved, IGG allows close and distant relatives from both, maternal and paternal sides to be identified (4,11).…”

“…Instead of governmental authorities, these genetic genealogy databases are managed by private companies or private citizens, such as GEDmatch consisting of around 1.3 million high-density SNP profiles as of 2020 (12). The most commonly used method for identifying relatives in IGG is via DNA segments shared between the unknown perpetrator obtained from crime scene DNA and individuals in genomic databases (10,13,14). These identical-by-descend (IBD) segments that originate from the same ancestor signal a familial relation between the highlighted person in the genomic database and the unknown perpetrator, and the length of the shared segments translates into how close the family relationship is.…”

“…These identical-by-descend (IBD) segments that originate from the same ancestor signal a familial relation between the highlighted person in the genomic database and the unknown perpetrator, and the length of the shared segments translates into how close the family relationship is. Police investigation to find the unknown perpetrator is then focused on the highlighted relative via genealogical research (10).…”