The Killer Inside Us: Law, Ethics, and the Forensic Use of Family Genetics

24 Berkeley J. Crim. L. 47 (2019)

54 Pages Posted: 9 Apr 2019 Last revised: 13 Feb 2020

Date Written: January 7, 2019


A new era of criminal investigation has dawned in which decades-old cold cases are being solved through the forensic use of consumer genetic databases. Law enforcement increasingly harnesses the power of these databases to which individuals have uploaded their DNA in order to explore and understand their genealogy, health, and other highly personal attributes. By surreptitiously accessing these databases, law enforcement can track down criminal targets based on their family relation to any individuals populating the databases.

While a growing number of cases have figured prominently in law enforcement’s use of these databases—none has demonstrated the power and reach of these databases as much as the Golden State Killer case. As that case demonstrates, alongside this new genetic search capability, new legal and ethical concerns emerge.

This article identifies, through the example of the Golden State Killer case, those concerns and proposes the kind of balancing test that a court encountering a legal challenge to the forensic use of direct-to-consumer databases should perform. This challenge has not yet been made, but when it is, the courts will have to balance the potent crime-solving benefits of genetic search technology against the privacy interests of the various affected individuals. In the process, this article also examines applicable legal doctrine from various cases in which courts have grappled with expansive and probing technologies and their threat to reasonable expectations of privacy. Central foci are the courts’ mounting discomfort with the long-established third-party doctrine and, correspondingly, their emerging embrace of the equilibrium-adjustment theory of Fourth Amendment jurisprudence pursuant to which courts redraw Fourth Amendment protections as technology becomes more invasive.

Keywords: fourth amendment, genetics, golden state killer, carpenter, criminal law, third-party doctrine, genealogy, GEDmatch, genetic genealogy

Suggested Citation

Zabel, Joseph, The Killer Inside Us: Law, Ethics, and the Forensic Use of Family Genetics (January 7, 2019). 24 Berkeley J. Crim. L. 47 (2019), Available at SSRN: or

Joseph Zabel (Contact Author)

Stanford Law School ( email )

559 Nathan Abbott Way
Stanford, CA 94305
United States

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