Forensic genealogy, the practice of finding a perpetrator’s relatives by matching crime scene DNA against genetic ancestry databases, burst onto the scene in 2018 when investigators were able to identify the “Golden State Killer” through a distant relative. A month after the arrest of the serial murderer and rapist from California, genetic genealogy would again help authorities catch a lower-profile killer in Washington. The resulting case, which is now the first-ever criminal trial involving genetic genealogy, concluded in late June with a conviction. A jury found William Talbott II guilty on two counts for the 1987 murders of Tanya Van Cuylenborg and Jay Cook, a young Canadian couple.

Law enforcement officials explained in court that, after decades of making little progress in the case, they had finally made a breakthrough in 2017 with the help of genetic genealogists at Parabon NanoLabs, a leader in the field. The genealogists ran DNA collected from one of the victim’s clothing through the ancestry database GEDmatch, which people use to trace their family trees. The search identified a distant cousin of Talbott, providing a crucial lead for investigators.

The use of DNA genealogy in the criminal investigation has been the focus of coverage around this case, and rightly so. As of April, Parabon’s genetic genealogy tools have led to 49 suspect identifications, about 1,000 renewed investigations, and at least 17 arrests. With the rising popularity of genetic sleuthing, its role in helping to actually convict a suspect for the first time is a milestone in the burgeoning field. However, Parabon didn’t only try to help investigators locate family members of the suspect. According to the New York Times, the company first produced a digital likeness of the suspect’s face using the crime scene DNA. Authorities ultimately did not find it helpful, but the very fact that they tried is telling.

As genetic genealogy becomes more and more popular, DNA face imaging seems to be benefiting from the extra limelight. And now that DNA databases like GEDmatch have implemented restrictions that make it harder to conduct genetic genealogy searches, it’s possible that DNA phenotyping may become more prominent in investigations. “Time will tell,” Parabon Vice President Paula Armentrout wrote in an email. “If fewer cases are being solved via genetic genealogy then investigators will turn to the other tools that are available to them.”

Parabon has long hawked DNA-based suspect sketches alongside its better-known genetic genealogy services. The company’s first law enforcement product was in fact a face imaging service. Parabon began pursuing genetic genealogy for criminal investigations in earnest later on, when authorities apprehended the Golden State Killer using the method. Facial reconstruction, which academics say is not as scientifically sound, has seen a surge in popularity feeding off the rise of forensic genealogy. “[Face phenotyping’s] popularity was increasing prior to genetic genealogy, and certainly its popularity is improving because of genetic genealogy,” says Steven Armentrout, founder and CEO of Parabon. Police departments have increasingly used both offerings in conjunction since the arrest of the Golden State Killer.

The company now sells the facial phenotyping and genetic genealogy services side by side on its website. It offers basic facial phenotyping for hair and eye color along with its genealogy assessment for $1,500. The more advanced package, which includes facial morphology, costs an additional $2,250. The New York Times reported that police departments end up paying $4,000 to $5,000 in total per case. Besides Parabon, other DNA genealogy companies such as Identitas and Illumina offer similar phenotyping services. Parabon says it’s assisted authorities in the U.S., Sweden, and Canada in more than 350 cases using DNA phenotyping, roughly 200 of which involved facial morphology.

But the scientific community still doesn’t know much about how genes express themselves in forming a person’s face.

“All of the recent successes were from genetic genealogy, and [Parabon] tried to push the facial reconstruction as if it works, too,” says Yaniv Erlich, a computer science professor at Columbia University and chief science officer at the DNA testing company MyHeritage. He notes that the techniques use similar technology for identifying genetic markers, so it would be fairly convenient for the company to include them both in its offerings.

According to Kenneth Kidd, professor emeritus of genetics at Yale University School of Medicine, scientists over the past few years have learned more about which genes are more likely to produce certain facial features, but they still don’t thoroughly understand the mechanism. “So far what has been done is based on association—just that people with a tall forehead more frequently have this set of genetic variants,” Kidd says. “We have no understanding of the underlying developmental biology.” This is important because the same gene may express itself differently in different people. Even twins sharing the same DNA are not exactly identical; one may be a bit shorter or have a slightly wider nose. In addition, a person’s facial features change over time, so you’d have to know the age of the suspect you’re trying to reconstruct.

Facial phenotyping is somewhat reliable when it comes to determining a person’s hair, eye, and skin color, but it’s not that helpful in determining the shape of a face. Erlich says that the facial images that the technology produces often look very similar to each other for people of the same race and gender, which is why you might see some resemblances between a digital rendering and an actual picture. “If I give you a composite [face] image, I put it in the right angle, and I put the person next to it staring at the same angle, they will look similar,” he says. The ACLU has advised against using face phenotyping “for any serious purpose” in criminal investigations, warning that the technique produces “baseless information” that could ensnare innocent people, especially if police aren’t fully aware of its limitations.

The ACLU has advised against using face phenotyping “for any serious purpose” in criminal investigations.

Genetic genealogy, while not perfect, is still more reliable partly because it instead focuses on the DNA itself. The practice involves identifying gene patterns that people with similar ancestral origins share. The genes themselves won’t change with age, and the way in which they are expressed is less relevant. In fact, because genetic genealogy is so powerful, there are many more ethical concerns at the moment with that technology than there are with facial reconstructions. “The concern we have with [facial] phenotyping is that it’s not really based on sound science,” says Jay Stanley, an ACLU senior policy analyst. “With genealogical methods, that’s not the primary concern. It’s more that it’s a bit of a dragnet.” While facial phenotyping only requires the DNA of the suspect, forensic genealogy uses the DNA of the suspect along with that of innocent people, who might not know that law enforcement has access to their genetic profiles.

In short, Erlich and Kidd assert that Parabon is very likely overstating the effectiveness of its facial phenotyping technology, but that its genetic genealogy products have more grounding in scientific research. They both pointed out that Parabon has not released enough information about its phenotyping methods to allow for a proper peer review. Steven Armentrout, however, claims that evaluating the relative effectiveness of the two technologies is like comparing “apples and oranges,” because they serve different purposes in an investigation. Face phenotyping is meant to help police rule people out, rather than to identify the perpetrator, and the company makes no claims that the phenotype sketches are photorealistic. In response to the general sense of skepticism from some in the academic community toward Parabon’s facial reconstruction technology, Steven Armentrout says, “We’re trying to serve our customers. The increased demand for the tool and its success speaks for itself.”

Future Tense is a partnership of Slate, New America, and Arizona State University that examines emerging technologies, public policy, and society.