Reevaluating the Threshold Question in the wake of Carpenter and the path of the Golden State Killer

By Brady O’Bryan*

Introduction

Between 1974 and 1986, a string of brutal rapes and murders terrorized California.¹ Though the crimes spread across ten different counties, their similarities led law enforcement to suspect that the perpetrator was a single man—"The Golden State Killer" ("GSK").² Until recently, efforts to identify the sadistic criminal had produced little more than rough sketches.³ Then, Paul Holes, a crafty investigator and DNA expert, wondered if the recent rise of commercial genealogy databases could provide the spark in a case that had run four-decades cold.⁴ As it turns out, law enforcement had long held a sample of GSK’s DNA collected from a crime scene.⁵ However, because the sample did not match any profile in the government’s DNA databases, it was all but useless.⁶ Until now. In a stroke of genius, Holes sent in a sample of the DNA⁷ to GEDmatch.⁸ The open-source ancestry site established a connection to GSK’s great-great-great grandfather.⁹ From this point, investigators were able to craft a sprawling family tree that narrowed their search.¹⁰ That was all they needed to produce the case’s biggest break in 40 years—GSK had a name.

The investigation tactic has since inspired other law enforcement offices to do their own ancestry sleuthing, and understandably so.¹¹ Until now, DNA identification was limited because law enforcement’s database contained a small subset of the population—largely convicted felons.¹² Even with this limit, DNA identification is ubiquitous and a powerful tool for detectives and prosecutors bringing criminals to justice.¹³ Recent reporting indicates that the pool of profiles submitted to online genealogy services is large enough to identify sixty percent of white Americans; and that number is expected to rapidly increase in the coming years.¹⁴ It is no surprise that law enforcement wants to augment its existing database with open-source ancestry sites and someday gain the ability to identify every person in the country by DNA sample.¹⁵ It is the kind of power J. Edgar Hoover could only have dreamt of while painstakingly cataloging his fingerprint database.