Many states now have infant safe-haven laws to allow mothers to abandon babies legally. These laws did not exist 38 years ago.Steven Senne / AP

Thirty-eight years ago, an infant boy—hours old, tears frozen on his face—was found dead in a ditch in Sioux Falls, South Dakota. Last week, police arrested his mother and charged her with murder, after investigators uploaded the baby’s DNA to a genealogy website and matched her relatives.

The same strategy led police to the Golden State Killer suspect in April 2018, and since then law enforcement working with genealogists have made dozens of arrests for rape and murder around the country. Once a headline-grabbing technique, forensic genealogy has become quietly normalized. Now this powerful tool, first used to catch a serial killer, is being applied to abandoned-baby cases that genealogists once hesitated to take on.

More dead and abandoned babies are likely to be identified soon. The Sioux Falls police worked with a forensics company called Parabon NanoLabs, which opened a dedicated genealogy unit after the surge in interest following the Golden State Killer case. Another company called IdentiFinders, run by the forensic genealogist Colleen Fitzpatrick, says it is working on three abandoned-baby cases.

One such case—the death of a baby boy found frozen in Connecticut in 1998—has been in the works since before the Golden State Killer, and its arc demonstrates how much attitudes have changed. This baby was supposed to be the first case of a nonprofit, the DNA Doe Project, that Fitzpatrick founded with Margaret Press in 2017. They planned to use genealogy to identify John and Jane Does, and Fitzpatrick and Press even paid to sequence the Connecticut baby’s DNA out of their own pocket. But over and over again, people advised against taking the case. One medical examiner even told the team she would not work with the DNA Doe Project if it tried to identify dead babies.

At the time, using genealogy databases for cold cases was still controversial. Finding the mother of an abandoned baby did not seem like a good test case. “What if you find a 16-year-old girl who was raped by her father and years later we haul her off to jail?” Press says. They feared a backlash would shut off their access to genealogy websites forever.

Then, police arrested Joseph James DeAngelo as the Golden State Killer, the infamous serial killer and rapist who had terrorized California for decades. “It was a good poster case for the cause,” Press says. In fact, it’s hard to imagine a better one. The case has since spawned a forensic-genealogy industry. Parabon announced its new genealogy unit just weeks after the case. Recently, another forensics lab called Bode Technology launched a similar service. Fitzpatrick’s company, IdentiFinders, uses genealogy to ID perpetrators, including in the Connecticut baby case, and the nonprofit DNA Doe Project works on unidentified bodies, most of them murder victims. So many arrests have been made through genealogy that each one is no longer national news.

The Sioux Falls case has gotten more attention because it involved a dead baby, but it has kicked up very little of the controversy that genealogists once feared. “We’re in a different world now,” Fitzpatrick says. The woman arrested in Sioux Fall, Theresa Rose Bentaas, confessed to abandoning her baby hours after birth in 1981, when she was 19. The public details are scant, but police also interviewed the father—to whom Bentaas is now married—and determined he did not know of the pregnancy. Bentaas alone was charged with murder in the first degree, murder in the second degree, and manslaughter in the second degree.

The killing of a infant within the first 24 hours of life is called neonaticide, and Michelle Oberman, a law professor at Santa Clara University who has studied the issue, says there are probably hundreds of cases every year. The criminal-justice system is not always sure how to deal with them. Charges can range from unlawful disposal of a body to first-degree murder.

In general, Oberman says, “There’s a pretty distinct pattern of overcharging and under-convicting.” Because the cases can be so shocking and incomprehensible, Oberman says prosecutors sometimes ask for murder charges and very long sentences. Many of the women—or girls—desperate enough to abandon their babies are isolated and come from tough family situations. The fathers are usually not in the picture. “When they do go to trial, if it does happen, juries tend to recognize there’s blood on more than one set of hands,” Oberman says. These are complicated cases.

Currently, no laws limit when police can use genealogy databases to catch criminals. (A legislator in Maryland has proposed a law outlawing the practice in that state.) But genealogists have so far limited their criminal investigations to violent crimes, per the terms of service of GEDmatch, the public genealogy site where they upload crime-scene DNA. Steven Armentrout, CEO of Parabon, told me that his company follows those terms of service, and it was police who determined the Sioux Falls case to be a murder case. When I asked Armentrout about regulating how genealogy should be used, he pointed out that police don’t have special access to GEDmatch. “Police can do anything an ordinary citizen can do. We’re using a publicly available database,” he said.

As the use of genealogy to solve crimes becomes routine, some wonder how far it will go. Debbie Kennett, a genealogist in the U.K., says she was “horrified” by the use of genealogy in this case and feared a slippery slope. She points to a case in Georgia in which investigators decided to test DNA from a fetus found in a sewage plant. (It’s unclear whether they were only trying to upload the DNA to law-enforcement databases or also consumer genealogy ones.) The fetus was later found to be the result of a miscarriage, but DNA could theoretically be used to investigate illegal abortions.

In most cold cases, arresting the murderer or identifying the victim is a way to bring resolution to the victim’s family. Identifying the mother of a dead and abandoned baby is different. “Ultimately it’s about punishment, not about closure for a family,” Press says.

At the press conference announcing the arrest in Sioux Falls, police too acknowledged the unusualness of this case. “When we have cases like this, we have family that we can—it’s not share the joy, because there’s nothing joyous about it—but at least let them know we work hard for them,” the detective said. This case was different, he admitted. “We didn’t have that in this case. In this case, the family is the person that did it.” For 38 years, they had kept the case alive. It is solved now, but there is no family to thank them for their work.

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