In July 2000, a researcher walking a remote stretch of Olympic National Park found a tent with a skeleton inside it. There were binoculars, a day pack, a saw, some winter gear, and nothing at all to say who the man had been. For twenty-six years he was a case number in a federal database of the unidentified.
This summer he got his name back. A DNA profile built from the remains led investigators to first cousins on both sides of his family, who provided their own samples, and the National Park Service identified him as Joseph Louis Serrao Jr., born in 1960. The county coroner ruled the death a suicide. It is difficult to read that story and see anything but a good outcome: a family that stopped wondering.
The same technique that returned Mr. Serrao’s name to his family is now routinely used to build homicide and sexual assault prosecutions, and in that setting it raises questions that North Carolina courts have barely begun to answer.
How Investigative Genetic Genealogy Works
Traditional forensic DNA compares a small number of markers against CODIS, the government’s offender and arrestee database. If there is no match, the trail ends. Forensic genetic genealogy takes a different path. A laboratory develops a dense genome-wide profile from crime scene material and uploads it to consumer ancestry databases that permit law enforcement searching. The search returns not a suspect but partial matches: second cousins, third cousins, people who may never have heard of the defendant.
Genealogists then build family trees backward from those matches, using obituaries, marriage records, census data, and social media, until the tree narrows to a small group of people who fit the age, geography, and sex of the unknown contributor. Investigators surveil the candidate and collect something he discarded, a coffee cup or a cigarette, and run a conventional comparison against that abandoned sample. The report that reaches the courtroom describes only that final, ordinary comparison.
The Golden State Killer identification in 2018 made the technique famous. Hundreds of cases have followed, many of them decades old.
Why the Fourth Amendment Has Not Done Much Work Here
Defendants have challenged these searches with limited success, largely because of standing. A defendant generally cannot complain about a search of a database entry that a third cousin voluntarily uploaded. The genetic information that exposed him belongs, in the law’s view, to someone else. Courts have also leaned on the abandonment doctrine to uphold the surreptitious collection of the confirmatory sample, reasoning that a discarded cup carries no reasonable expectation of privacy.
Whether that reasoning survives contact with modern genetics is a fair question. The Supreme Court’s more recent decisions have shown some willingness to treat digital-age aggregation differently from the older third-party cases, and a person’s genome is not a phone record. But the arguments are unsettled, and a defense that rests entirely on suppression is a defense with a thin margin.
The Discovery Problem Is the Real Fight
The more practical issue is that prosecutors frequently characterize the genealogy work as an investigative lead rather than evidence. Because the State intends to offer only the direct comparison at trial, the argument goes, the genealogical process is not discoverable and does not require validation.
That framing should not go unchallenged. Defense counsel should be asking which database was searched and under what terms of service, whether the terms permitted law enforcement use, who performed the genealogical analysis and with what qualifications, how many candidate individuals were considered and excluded, what assumptions about parentage the tree relied on, and whether any relative was interviewed under a pretext. Private laboratories perform much of this work under proprietary methods, which raises validation questions familiar from other disciplines. Whoever reached the conclusions should be the witness who defends them, an issue North Carolina appellate courts continue to take seriously, as we discussed in our analysis of State v. Clark and the Confrontation Clause.
Cold cases carry their own evidentiary weakness. Witnesses die, memories degrade, and physical evidence may have been stored for decades under conditions nobody documented. A genetic identification tells the jury who contributed a sample; it does not establish when the sample was deposited or what happened. Sufficiency of the evidence remains a live question in old homicide prosecutions, as our discussion of State v. Massey and felony murder reflects.
Regulation Has Not Caught Up
The Department of Justice adopted an interim policy in 2019 limiting federal use of the technique to violent crimes and unidentified remains and requiring compliance with database terms of service. It is an internal policy. It creates no rights a defendant can enforce, and it does not bind state and local agencies at all.
A handful of states, Maryland most comprehensively, have passed statutes requiring judicial authorization and imposing procedural limits on genetic genealogy investigations. North Carolina has enacted nothing comparable. In this state the practice is governed by whatever the investigating agency decides is appropriate, subject only to constitutional argument in individual cases.
None of this makes the technique illegitimate. The Serrao identification is a reminder of what it can do when it is used to answer a question rather than to build a case. But a method powerful enough to find one man in a national database from a third cousin’s saliva sample deserves scrutiny when its output is a criminal charge.
If you or a family member has been contacted by investigators about a cold case, or asked to provide a DNA sample voluntarily, talk to a lawyer before you do anything. Damon Chetson is a Board Certified Specialist in State and Federal Criminal Law who has tried homicide cases built on forensic evidence. Our Raleigh criminal defense practice is available for a confidential consultation at 19 W. Hargett Street, Suite 400.