How forensic genome sequencing can extend the search in Nancy Guthrie investigation

Federal investigators say a glove found about two miles from Nancy Guthrie’s Tucson home did not produce a match in the FBI’s CODIS database. Still, that “no-hit” result isn’t a dead end. The glove has become a focal point in a wider forensic effort, with investigators weighing a range of more advanced techniques that can sometimes squeeze leads out of limited or degraded biological material.

What a CODIS no-hit actually means
CODIS is built to flag exact matches or very close familial links among profiles already in the system. If a suspect or a near relative isn’t in CODIS, the system simply won’t light up. That doesn’t mean the sample is useless—only that routine database comparison didn’t identify a match.

When labs want to push beyond CODIS
Forensic teams have several options beyond standard STR testing. Forensic-grade genome sequencing reads far larger stretches of DNA and can recover information from samples that routine assays can’t interpret. Next-generation sequencing and specialized extraction protocols can help when DNA is old, fragmented or present in tiny amounts. Analysts may also attempt familial searching or genetic genealogy—methods that search for relatives rather than exact matches and can point investigators toward family trees that merit further scrutiny.

Each of these paths demands meticulous lab work and careful interpretation. Sample quality, laboratory technique and the availability of comparative records all affect whether additional testing will yield usable leads. And when results are destined for court, validation and defensible chain-of-custody procedures are essential.

How sequencing and genealogy work together
Sequencing produces a high-resolution genetic snapshot. Genetic genealogy turns that snapshot into possible family connections by comparing profiles to broader public and private datasets, then building and pruning candidate family trees using records like census data, obituaries and voter registries. It’s a hybrid pursuit—part molecular science, part genealogical shoe-leather.

That combination has cracked long-cold cases, but it isn’t a guaranteed shortcut. A promising distant-relative hit often yields many possible branches to investigate, and confirming which branch contains the person of interest takes time and traditional detective work.

Policy and privacy: patchwork rules
Whether investigators can use these tools—particularly genetic genealogy—depends on law, local practice and the terms of the databases they consult. Some jurisdictions allow investigators to search public genealogy databases; others restrict access or require warrants. Those differences shape timelines and scope, and they affect what information agencies can share publicly.

Expanding technical capability increases the chance of finding leads, but without clear policies and oversight, it raises privacy and civil-liberties questions. Responsible deployment typically involves transparent rules, judicial review when appropriate, and safeguards to limit misuse and protect sensitive data.

Timing and investigative workflow
After a no-hit in CODIS, labs usually reassess the sample: evaluating how degraded it is, choosing the best extraction method, and deciding whether sequencing or targeted testing is worth the cost and effort. That triage informs how quickly additional analyses can proceed. Forensic testing can take weeks to months, depending on backlog, the complexity of the sample and legal or procedural hurdles.

How forensic evidence fits into the bigger picture
DNA is often just one thread in an investigation. Physical evidence like the glove must be integrated with other streams—witness accounts, digital records, surveillance footage, cell‑site data and traditional police work. Each piece can corroborate or redirect lines of inquiry; combined thoughtfully, they transform ambiguous leads into actionable avenues.