Investigative Genetic Genealogy and the Problem of Familial Forensic Identification

Abstract

Since the April 2018 arrest of the alleged Golden State Killer, law enforcement investigators have made arrests in a remarkable string of cold cases. In dozens of cases, investigators compared preserved crime DNA to other DNA profiles in an online genealogy database. These searches, in turn, uncovered partial genetic matches to known but distant genetic relatives of a putative suspect. Through sleuthing in the resulting family tree or trees, investigators have been able to identify suspects for investigation and, in some instances, arrest, prosecution, and conviction.

Proponents of using consumer genetics platforms to investigate and solve crimes have argued that the genetic data on which those investigations rely has been voluntarily uploaded and shared. Yet, in nearly every case thus far announced, the individual ultimately arrested did not himself upload his identifiable genetic information to a consumer genetics platform. Rather, he was identified through a match between crime scene DNA and the profile of a genetic relative—often a distant one. In other words, the individuals identified as suspects did not voluntarily upload their genetic data to a consumer genetics platform.

Indeed, voluntariness is a poor fit for genetic relationships. This article unpacks the disjunction between genetic relatedness and voluntariness, and the challenges that disjunction poses for law enforcement use of consumer genetics platforms. While resolving cold cases and bringing wrongdoers to justice is laudable, genetic genealogy’s reliance on matches between genetic relatives should prompt serious questions about whose identifying genetic data is included in law enforcement searches and with what justification.