What Is Whole Genome Sequencing, and How Might It Change the Outcome of the Gilgo Beach Killer Trial?

Whole genome sequencing can determine the complete DNA sequence of an organism’s genome from just one genetic sample. Its medical uses vary from researching bacterial pathogens to delivering individualized treatments to patients.

In criminal forensics, WGS can provide results when traditional DNA testing comes up short. It has helped identify human remains and solve cold cases, and is starting to appear in criminal proceedings.

At the upcoming trial of Rex Heuermann for the Gilgo Beach murders—named because several of his victims were discovered close to that Long Island, N.Y., location—a judge ruled DNA evidence obtained by WGS could be presented. It’s the first time a New York court will admit WGS findings.

Short tandem repeats (also called microsatellites) are repetitive DNA sequences found in the genome whose lengths vary between individuals. Police and federal investigators started using STR testing on DNA found at crime scenes in the 1990s, and it became the standard method for forensic DNA analysis.

Law enforcement runs STR profiles through the Combined DNA Index System (CODIS) database, which contains DNA profiles from convicted offenders, arrestees (when permitted by state law) and crime scenes.

But STR testing has limitations. David Mittelman, a scientist and the CEO of forensics lab Othram, tells A&E Crime + Investigation, “STR testing is fundamentally constrained because it only produces results when the person or a first-degree relative is already in CODIS.”

“Whole genome sequencing, as its name implies, attempts to collect the entire sequence of all chromosomes, including the mitochondrial chromosome,” Nathan Lents, a biology professor at John Jay College of Criminal Justice, tells A&E Crime + Investigation. “Within the whole genome are all of the microsatellite [STR] sequences—the genetic fingerprints used in standard forensic DNA profiling—so those matches will be possible. But in addition, a couple of million other tiny differences—called single nucleotide polymorphisms, SNPs for short—will also be captured.”

Andrea McCarthy, an accredited investigative genetic genealogist, executive director of the Cold Case Coalition and co-director of forensic investigative genetic genealogy for Intermountain Forensics, tells A&E Crime + Investigation that in her line of work they only use use SNP profiles rather than STR profiles.

She explains that SNP profiles are uploaded to one of the law enforcement accessible databases like GEDmatch, FamilyTreeDNA, or DNA Justice, and then they “look at DNA relatives—often distant cousins—of our unknown DNA to build genetic networks which ideally results in an identification.”

Othram uses Forensic-Grade Genome Sequencing, a specialized form of whole genome sequencing the company developed specifically for forensic applications. Mittelman notes that Othram used FGGS in the Bryan Kohberger case.

Kohberger killed four University of Idaho students in November 2022. When law enforcement couldn’t find CODIS matches to DNA found on a knife sheath left at the crime scene, investigators turned to Othram. The company employed a genetic profile to build a family tree that helped locate Kohberger.

Another issue with STR testing is “it often fails when working with degraded or chemically compromised DNA,” Mittelman explains.

But WGS can often deliver results.

“Othram has successfully developed genomewide data from a wide variety of forensic materials, including skeletal remains, hair shafts, bone fragments, degraded tissue, cigarette butts, fabric, bodily fluids and sexual assault kits,” Mittelman says. “Many of these samples are decades old and were previously considered unsuitable for traditional forensic DNA testing.”

The remains of the seven women Heuermann has been charged with killing were discovered on Long Island between 1993 and 2011. Rootless hairs were recovered from six of the women, but the DNA they contained was old and fragmented. However, Astrea Forensics was able to use WGS and link Heuermann to those hairs, according to prosecutors.

“WGS is especially useful with degraded DNA because recovery of even a small percentage of the genome will still provide a wealth of markers that can be used to generate a unique profile,” biology professor Lents says.

At Othram, Mittelman says, “FGGS is most often applied to unidentified human remains cases and unsolved violent crimes, particularly when traditional STR testing fails to produce a CODIS match.”

Othram helped police identify a suspect in the murder of Tina Heins, who was stabbed to death in Florida on April 17, 1994. Her brother-in-law was convicted of the crime, but was released from prison in 2007 after testing showed he wasn’t a match for DNA found at the scene.

Othram linked the unknown DNA to a friend who’d been at Heins’s wedding. Michael Shane Ziegler was arrested for the murder in September 2025 and charged the next month.

Lents says WGS was first used in a criminal trial in Idaho in 2024. David Dalrymple had already been serving a life sentence for a similar crime when he was convicted of the 1982 murder of 9-year-old Daralyn Johnson using DNA evidence extracted from rootless hairs that had been collected from the victim’s underwear more than 40 years prior.

Its use in California, Idaho and New York courtrooms doesn’t mean that other jurisdictions will automatically accept WGS results, Michael Benza, a professor at Case Western Reserve University’s School of Law, tells A&E Crime + Investigation.

Benza explains that different court systems will hold admissibility hearings and evaluate WGS like they would any new science: “Court by court, state by state, would have to make those decisions.”

Additional factors could affect the adoption of WGS in forensics.

“WGS is much more expensive and labor-intensive, so we will see it being used in special cases like very high-profile crimes in which the samples are old or degraded, missing persons and other cases where we have a DNA sample but it doesn’t match anything in the databases, and other cold cases where other investigative leads have been exhausted,” Lents says.

And because WGS provides extensive genetic information, Lents adds, “We will need a lot of legal and ethical safeguards around the practice of law enforcement obtaining entire genomes from innocent citizens without their knowledge or consent.”