Overview of Genetic Genealogy and DNA Evidence — Part 3 of Megyn Kelly Investigates Nancy Guthrie's Disappearance (Ep. 1276)
This episode (part 3 of a four-part series) focuses on the forensic DNA work and unanswered scientific questions in the disappearance of 84-year-old Nancy Guthrie. Host Megyn Kelly interviews forensic DNA expert Susanna Ryan and security specialists James Hamilton (former FBI supervisory special agent) and Will Geddes (security consultant) to explain what DNA evidence can — and can’t — tell investigators, what techniques are likely being used, why there are public gaps in what’s reported, and how scene handling, mixed samples, and database access affect the chances of identifying a suspect.
Key points and main takeaways
- Authorities reported finding DNA at Nancy’s home that does not belong to her or people in close contact with her; publicly they’ve said it’s a mixed profile (more than one contributor).
- Mixed DNA complicates genetic genealogy: traditional STR testing (used for court and CODIS) is different from SNP testing (needed for genetic genealogy). SNP profiles require more DNA and are much harder to deconvolute when mixed contributors are present.
- If enough DNA remains, investigators can perform SNP testing and upload the profile to searchable public genealogy databases (GEDmatch Pro, FamilyTreeDNA). Private consumer databases (23andMe, Ancestry) generally do not allow law enforcement searches without policy changes or special arrangements.
- Genetic genealogy is powerful: it can identify relatives (even distant ones) measured in centimorgans, enabling genealogists to build family trees and narrow suspects — but it’s time-consuming, especially when matches are distant.
- Phenotyping (companies like Parabon) can produce composite images from DNA that suggest ancestry, hair/eye color, facial shape and other traits — useful as an investigative lead if the DNA profile is single-source or largely dominant.
- CODIS familial searching (searching for near-matches like parent/child/sibling) is allowed only in some states (~11–12) and requires a special request.
- Investigators must prioritize sampling points likely to yield perpetrator DNA (points of entry/exit, doorknobs, light switches, bedding, remnants of items like a Nest camera or flashlight). Tools such as an MVAC (wet vacuum) can pull substantially more trace DNA from porous items (bedding, upholstery) than swabs.
- Contamination and scene control are major concerns: investigator-mediated transfer, cross-contamination, environmental exposure (outdoor mats, items left outside) can degrade evidentiary value or confuse mixtures.
- Publicly, no CODIS or genetic genealogy match has been reported; sources cited on the show suggest law enforcement has no confirmed suspect (reports vary on whether they have leads being actively developed).
- FBI billboards were placed in AZ, CA, NM, TX (notably Houston); commentators suggest this could indicate some inferred geographic/ethnic direction from investigative leads, but the placement could reflect many strategic considerations.
Topics discussed (broken out)
Forensic testing methods and sequences
- STR (short tandem repeat) testing: standard forensic profile used for CODIS matches and courtroom confirmation.
- SNP (single nucleotide polymorphism) testing: required for genetic genealogy and phenotyping; needs more and cleaner DNA, and is more sensitive to mixtures.
- Familial searching in CODIS: possible in some states to find near-matches (e.g., parent/child, siblings). Must be specially authorized.
Genetic genealogy & phenotyping
- Genetic genealogy uses centimorgan shared amounts to estimate relationships (parents ~50%, siblings ~50% on average, cousins less) and genealogists build family trees from matches.
- Phenotyping (e.g., Parabon) can suggest physical features and ancestry from SNP data — useful as an investigative lead when single-source or dominant contributor data allow it.
Practical evidence collection
- Priority locations: points of entry/exit, bedding, light switches, doorknobs, remnants of electronics, items moved or out-of-place.
- Tools: MVAC (wet vacuum) for large porous items; multiple glove changes and strict evidence handling to avoid contamination.
- Mixed DNA: routine for STRs, but problematic for SNP genealogy when minor contributors are low-percentage or when 3–4 contributors are present.
Investigative and interagency considerations
- Database access limitations (private consumer services vs. public genealogy) impact speed and scope of searches.
- Law enforcement may keep results and investigative paths confidential; public reporting can lag or be partial.
- Coordination between Pima County and FBI (task force structure, information flow) was questioned by guests.
Theories and context raised by panel
- Possibility of a transnational criminal crew (South American/Mexican criminal groups) invoked because:
- No public matches in US criminal databases
- FBI billboards targeted to states with large Mexican populations (theories drawn by commentators)
- Video examples of groups breaking in using similar clothing/gear were discussed
- Counterpoints: removing a body, motive, and victimology may suggest targeted act rather than simple B&E; investigators may be pursuing methodical leads and building a case quietly.
Notable expert insights & quotes
- Susanna Ryan: SNP/genealogy testing is "a totally different type of testing" and "you need enough sample remaining" — mixtures make SNP work much harder.
- On mixtures: "If the person of interest is the major contributor, labs can deal with it; if the person is a minor component (≈20–25%) or there are 3–4 contributors, it becomes almost impossible" for genealogy.
- On evidence collection: MVAC (wet vacuum) can "pick up greater quantities of DNA, sometimes dozens of times more" than swabbing.
- On the investigatory timeline and confidentiality: genetic genealogy and family-tree-based investigation "can be very time consuming" and investigators may be working behind the scenes for months.
- Panel critique of local leadership/communication: the Pima County sheriff's public statements and compartmentalization of information were questioned; guests urged better transparency and task-force framing.
Examples referenced (illustrative precedents)
- Boy in the Box (1950s case): identified years later through genetic genealogy.
- Kohlberger case: trash pull and familial identification that led to father/son confirmation via traditional STR comparison.
- Parabon phenotyping (Andrea Canning example): composite generated from DNA showed general facial structure and traits that resembled the subject.
Public-facing items & timeline notes mentioned
- Pima County announced mixed DNA found that doesn't match Nancy or close contacts.
- No public report yet of CODIS matches or genetic genealogy leads.
- FBI billboards posted in Arizona, California, New Mexico and Texas (Houston highlighted in discussion).
- Family members reportedly passed polygraphs (coverage notes: polygraph results are not binary "pass with flying colors" in formal terms).
- Sister/brother-in-law’s car (last vehicle Nancy was seen in) was impounded and returned after several weeks; guests said extended hold could reflect extensive forensic work.
Recommendations / action items (what investigators should or could do; what the public can do)
For investigators:
- Prioritize re-testing and MVAC collection for bedding, points of contact around Nancy’s bed and other likely touched areas.
- Ensure strict contamination controls and document chain-of-custody; consider re-examining earlier-collected items for missed DNA.
- Use familial CODIS searches where allowed, and proceed with SNP/genetic genealogy when single-source or dominant contributor profiles are available.
- Consider targeted outreach (billboards, media) that includes suspect imagery/clear language (e.g., “abducted”) to maximize public recognition, while balancing investigative risks.
For the public:
- If you live or travel in the areas highlighted (AZ, CA, NM, TX) and recognize the man or vehicle, call the FBI tip line published by investigators.
- Avoid online speculation about private individuals; tips should go to investigators who can vet and follow up.
Bottom line
DNA offers the best realistic path to identifying the person(s) responsible — but the technical and practical hurdles are significant: mixed samples, limited DNA quantity, database access restrictions, contamination risks, and lengthy genealogy work. The panel believes it’s possible DNA will solve the case, but that outcome depends on whether single-source or dominant contributor DNA can be isolated and then run through the appropriate genealogy/forensic channels — a process that often happens behind the scenes and can take weeks to months.
Next episode (part 4): Ashley Banfield discusses on-the-ground reporting and where the investigation stands from her reporting.