Put simply, IGG describes the process of using information about genetic similarities and known family relationships to generate investigative leads. The basic information used in IGG falls into two categories: genetic relative information, which is generated by a genetic genealogy database based on its internal comparison of SNP profiles in the database; and genealogical and other often publicly accessible information, such as information from census records and obituaries, that describes family relationships.
Law enforcement integrates these two categories of information to develop family trees and then identifies and investigates high-likelihood suspects within those trees.
Thus, IGG comprises two steps that are book-ended by standard police work. According to best practices, when an offender leaves a biological sample (e.g., blood or semen) at a crime scene, an accredited forensic laboratory first generates an STR profile from that sample, which is called the ‘forensic sample.’
If there are no suspects, the STR profile is then uploaded to CODIS to identify a possible match with any of the 18 million-plus profiles in the database. If the forensic STR profile matches a CODIS profile, following manual confirmation of the match to ensure no administrative errors occurred in connection with analysis of the CODIS sample, the name of the matching offender in CODIS is released to law enforcement as an investigative lead.
The above is a portion of an article from Journal of Law and the Biosciences, Volume 8, Issue 1, January-June 2021, lsab001, https://doi.org/10.1093/jlb/lsab001
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