The latest report on the investigation into Nancy Guthrie focuses on why the FBI’s DNA testing process has taken so long despite the case remaining active for more than 100 days.
According to forensic DNA expert Tiffany Roy, the delay is largely due to the complexity of the evidence and the number of laboratories involved in the analysis. Roy explained that investigators are not simply testing DNA to identify whether it belongs to Nancy Guthrie — they are also attempting to identify unknown contributors connected to the crime scene.
Authorities previously confirmed that blood was found at Nancy Guthrie’s Tucson-area home after investigators concluded she had likely been abducted. However, officials have not publicly revealed whether all the DNA evidence belongs to Guthrie, the suspect, or multiple individuals. Roy said there are indications investigators may be dealing with a “mixed sample,” which significantly complicates forensic work.
Roy explained that five different laboratories have reportedly participated in different stages of testing. She noted that when DNA is found but does not immediately match anyone in law-enforcement databases, investigators may turn to genetic genealogy techniques. That process involves building family trees through distant DNA matches to eventually narrow down possible identities.
She emphasized that genealogy research is extremely time-consuming because analysts must trace genetic lines through large family networks and historical records before investigators can confidently identify a suspect. She also said some DNA mixtures are not suitable for genealogy testing at all, meaning scientists may need additional processing or alternative methods.
The delays have also become part of a growing dispute between the FBI and local investigators. FBI Director Kash Patel recently criticized the early handling of the case, claiming federal investigators were not immediately brought into the investigation and suggesting valuable evidence-processing time may have been lost.
Meanwhile, Pima County Sheriff Chris Nanos has defended the secrecy surrounding the evidence, arguing that releasing detailed forensic information could damage the integrity of any future prosecution. He stated that laboratories are still actively working on identifying the unknown DNA contributor connected to the case.
The case remains unsolved. Investigators continue reviewing forensic evidence, surveillance footage, and public tips while Savannah Guthrie and her family continue public appeals for information about Nancy’s whereabouts.
