Forensic Genetic Genealogy & Investigative DNA
How law enforcement can use SNP-based forensic profiles, genetic-genealogy services, family-tree research, traditional investigation, discarded DNA, and confirmatory STR testing to generate and validate investigative leads—and why this powerful technique raises distinct questions involving privacy, consent, database rules, state legislation, laboratory practice, disclosure, and constitutional law.
What this explainer does
Forensic genetic genealogy—often called FGG or investigative genetic genealogy—uses a DNA profile developed from forensic evidence to search a genealogy service for people who may be biological relatives of the unknown source.
The technique is fundamentally different from a conventional CODIS search. CODIS ordinarily compares forensic short tandem repeat, or STR, profiles against qualifying law-enforcement DNA profiles. FGG generally requires a much denser single nucleotide polymorphism, or SNP, profile that can reveal relationships across much more distant branches of a family.
A genealogy association is an investigative lead—not proof that the identified person left the crime-scene DNA. A sound investigation independently confirms identity through ordinary investigative evidence and, where appropriate, conventional forensic DNA testing.
Genetic genealogy is now an established investigative technique for some unsolved violent crimes and unidentified human remains, but legal regulation is uneven. Federal DOJ guidance, database terms, laboratory requirements, prosecutorial practices, and state statutes may impose different thresholds and safeguards.
Maryland and Utah have enacted detailed statutory frameworks, while other jurisdictions regulate genetic-data disclosure through broader privacy laws. Agencies therefore should not assume that a technique permissible in one state may be used identically in another.
1. Overview
Forensic genetic genealogy combines forensic DNA analysis with genealogy research to generate investigative leads when ordinary DNA database searching has not identified the source.
A forensic sample may come from biological material recovered at a homicide, sexual assault, kidnapping, unidentified-human-remains case, or another qualifying investigation. A laboratory develops a profile containing many genetic markers suitable for relative matching. That profile can then be compared, where law and database policy permit, against participating genealogy-service profiles.
The result is usually not a direct identification. Investigators or genealogists may instead receive one or more possible relatives whose amount of shared DNA suggests a relationship range. Genealogical research then attempts to reconstruct family lines connecting those matches to the unknown forensic source.
2. FGG Is Not the Same as CODIS
| Issue | Traditional CODIS / STR Comparison | Forensic Genetic Genealogy |
|---|---|---|
| Typical profile | Short tandem repeat (STR) loci used for forensic identification | Dense SNP-based profile containing far more markers |
| Primary search objective | Locate an identical or qualifying forensic/offender match | Locate biological relatives of an unknown source |
| Database environment | Government forensic DNA system governed by CODIS rules | Genealogy services containing consumer or user-submitted profiles, subject to law and service rules |
| Result | Potential direct forensic match or defined familial-search result where authorized | Genetic association requiring genealogy research and additional investigation |
| Amount of genetic information | Comparatively limited identification-focused forensic markers | Far denser marker set capable of revealing biological relationships |
| Investigative function | Forensic identification | Lead generation |
| Final confirmation | Laboratory match procedures under applicable forensic standards | Should not rely on genealogy alone; candidate identity is independently investigated and DNA-confirmed when appropriate |
3. How Forensic Genetic Genealogy Works
Step 1 — Start with biological evidence from the investigation
Investigators must have biological material that can lawfully be analyzed and that is sufficiently associated with the unknown perpetrator, victim, missing person, or unidentified human remains to justify further testing.
Step 2 — Perform traditional forensic analysis where appropriate
Under the DOJ framework and many agency practices, a CODIS-eligible forensic profile is searched through ordinary forensic systems first. FGG is generally considered when conventional methods have not produced a probative identification.
Step 3 — Develop a genealogy-compatible genetic profile
A qualified laboratory analyzes the forensic material using SNP-based or other suitable sequencing methods capable of producing a profile that can be compared for biological relatedness.
Step 4 — Search an authorized genealogy service
The forensic profile is uploaded or otherwise compared through a service that permits the intended law-enforcement use. Database rules matter: a service may permit law-enforcement access broadly, restrict it to users who have opted in, limit eligible crimes, or prohibit some forms of investigative use.
Step 5 — Evaluate genetic relationships
Potential relatives are assessed using the amount and pattern of shared DNA. The result commonly suggests relationship ranges rather than a single deterministic family connection.
Step 6 — Conduct documentary genealogy research
Genealogists use public records and other lawful sources—such as birth, marriage, death, obituary, census, newspaper, property, social-media, and family-history information—to build trees and identify candidate family lines.
Step 7 — Return to ordinary police investigation
Age, sex, geography, chronology, criminal history, vehicle records, employment, witnesses, known associations, travel, and other evidence are used to narrow possible candidates.
Step 8 — Independently confirm the candidate
Where appropriate, investigators lawfully obtain a candidate reference sample or recover discarded biological material and use conventional forensic DNA analysis to determine whether the candidate can be included or excluded as the source.
4. A Defensible Investigative Sequence
5. Case Selection Matters
FGG is resource intensive and privacy sensitive. It should not automatically become the next investigative step whenever a CODIS search fails.
Unsolved homicide, sexual assault, kidnapping, and comparable serious offenses are the traditional core of FGG policy.
Genealogy can assist medical examiners, coroners, and investigators in restoring identity when conventional identification methods fail.
The biological sample should have a defensible connection to the unknown person whose identity the investigation seeks.
Broad genealogical searching for minor offenses can create proportionality, statutory, policy, and public-trust concerns.
Complex mixtures, contamination, degradation, or uncertain attribution can increase the risk of building a genealogy investigation around the wrong genetic source.
An agency should not use genealogy when it lacks resources to independently investigate and confirm the resulting lead.
6. Genealogy Databases Are Not Interchangeable
Law-enforcement access depends on both law and the rules of the particular genealogy service.
Some services expressly support law-enforcement matching under specified conditions. Others have prohibited or restricted investigative use, changed their policies over time, required warrants or legal process, or created user-controlled law-enforcement matching settings.
The practical consequence is important: investigators should preserve the service terms, privacy policy, law-enforcement guidance, opt-in or opt-out configuration, and account settings that were in effect when the search occurred.
7. Family-Tree Research Is Investigative Analysis
The genetic match is only the beginning. A genealogist may have to reconstruct multiple family branches, determine how apparently unrelated matches converge, account for adoptions or non-parental events, distinguish people with the same name, and place potential relatives in the correct geographic and chronological context.
Shared DNA can suggest plausible relationship ranges but often does not identify one unique genealogical relationship.
Genealogy conclusions depend on the accuracy and completeness of public records, family records, obituaries, databases, and researcher interpretation.
Adoption, donor conception, misattributed parentage, name changes, remarriage, informal family relationships, and incomplete records can disrupt apparently straightforward trees.
8. Third-Party Reference Samples Require Care
Investigators may sometimes ask relatives to provide DNA voluntarily to clarify a family branch or test a genealogical hypothesis. This can be highly informative, but it also creates privacy and consent concerns because a person's sample reveals biological information about relatives who did not provide a sample.
The DOJ interim policy directs investigators generally to seek informed consent before collecting a third-party reference sample for FGG, while recognizing limited case-specific circumstances where seeking consent could compromise investigative integrity.
9. Discarded DNA Is a Separate Legal Step
After genealogy and ordinary investigation identify a likely candidate, investigators may seek discarded biological material—such as a cup, straw, tissue, cigarette, food container, or other item—to compare the candidate's DNA with the forensic sample.
The constitutional treatment of abandoned property and DNA analysis varies by jurisdiction and by the nature of the analysis performed. Agencies should distinguish collecting an abandoned object from extracting and analyzing biological information found on it.
10. Genealogy Generates a Lead; Conventional DNA Confirms Identity
Investigative genealogy should not be treated as the final forensic identification.
Once a candidate is identified, investigators ordinarily return to STR-based forensic analysis or another validated comparison method using a lawfully obtained candidate sample. A discarded sample may be used as an investigative bridge, followed by a known reference sample obtained through consent, court order, warrant, booking authority, or another lawful process as applicable.
11. Fourth Amendment Questions Are Still Developing
The Supreme Court has not issued a decision specifically resolving the constitutionality of law-enforcement forensic genetic genealogy searches.
Existing doctrine addresses pieces of the problem: physical collection of DNA, analysis of forensic identification markers, information voluntarily shared with third parties, searches of digital databases, abandoned property, and informational privacy. But SNP-based genealogy raises a distinctive issue because a forensic profile can reveal biological relationships through information contributed by people who may have no connection to the investigation.
12. Maryland v. King: Important, but Not an FGG Case
In Maryland v. King, 569 U.S. 435 (2013), the Supreme Court held that when police make a valid arrest supported by probable cause for a serious offense and bring the person to the station for detention, taking and analyzing a cheek swab for DNA identification can be a reasonable booking procedure under the Fourth Amendment.
The Court emphasized the limited identification-focused CODIS analysis before it. The opinion noted that the loci used did not, on the record then presented, reveal private medical or hereditary information and that the Maryland statute imposed safeguards on use.
13. State v. Westrom: What the Minnesota Supreme Court Actually Decided
State v. Westrom, 6 N.W.3d 145 (Minn. 2024), is one of the most important appellate cases arising from an investigation that used forensic genetic genealogy—but its holding is narrower than the case's genealogy background.
Investigators developed a SNP profile from DNA recovered at a 1993 murder scene and searched commercial genealogical databases. A potential first-cousin relationship helped investigators build a family tree that identified Jerry Westrom as a candidate. Officers later followed Westrom to a hockey game, recovered a napkin he discarded, and generated an STR profile that matched the crime-scene evidence. A warrant was then obtained for a known DNA sample.
On appeal, the Minnesota Supreme Court held that analysis of the DNA on the discarded napkin was not a search under the federal or Minnesota constitutions where the analysis was capable only of matching the DNA for identification. Critically, however, the court stated that Westrom had not challenged on appeal creation of the earlier SNP profile or the genealogical analysis.
The Minnesota court expressly declined to decide the potential privacy concerns associated with that SNP analysis. The U.S. Supreme Court denied Westrom's petition for certiorari on October 21, 2024.
14. Why Genetic Genealogy Creates Unusual Privacy Concerns
One person's genetic profile necessarily conveys information about biological relatives who may never have submitted DNA or consented to law-enforcement use.
SNP profiles contain far more genetic markers than traditional identification-focused CODIS profiles and can support relationship inference.
Genealogical analysis may reveal adoption, misattributed parentage, donor conception, unknown siblings, or other sensitive family information unrelated to the crime.
Users may have joined a genealogy service for ancestry research without anticipating law-enforcement searching, particularly under older terms of service.
Profiles generated for one investigation can create serious governance concerns if retained, reused, transferred, or searched for unrelated purposes.
Agency policy should prohibit analysis for disease predisposition, psychological traits, or other information unrelated to lawful identification purposes.
15. U.S. Department of Justice Interim Policy
DOJ's Interim Policy: Forensic Genetic Genealogical DNA Analysis and Searching, effective November 1, 2019, established a federal framework for investigative use of the technique. It remains a highly influential reference point even for nonfederal agencies.
The policy generally contemplates FGG after ordinary forensic methods, including CODIS where applicable, have been pursued without producing the needed lead. It also addresses case eligibility, laboratory processes, genealogy-service rules, third-party samples, covert collection, investigative confirmation, privacy, limitations on genetic use, and disposition of profiles and records.
FGG is generally positioned as a later investigative technique after ordinary forensic processes have failed to identify the source.
The federal framework requires attention to whether the genealogy service provides notice that law-enforcement searching may occur.
Informed consent, confidentiality, limited use, and careful handling of reference samples are recurring policy protections.
A genetic association must be followed by further investigation; genealogy is not a substitute for independent probable-cause development.
Genetic information should be used for identification purposes rather than medical, psychological, or unrelated trait analysis.
Case approval, testing, searching, genealogical analysis, investigative follow-up, reference samples, and confirmation should be reproducible and reviewable.
16. State Regulation Is Becoming a Major Part of FGG Law
States have taken different approaches. Some regulate law-enforcement genetic genealogy directly. Others regulate direct-to-consumer genetic data, provider disclosure, warrants, consent, genetic privacy, or law-enforcement access through broader statutory schemes.
This creates an unusually jurisdiction-sensitive technology. The legality of a database search may turn not only on the location of the investigating agency, but also on the statute governing the service, the consumer whose genetic data is disclosed, the laboratory, the location of the biological sample, or other choice-of-law questions.
17. Maryland Has a Detailed Judicial-Authorization Framework
Maryland enacted one of the nation's most detailed statutory schemes for forensic genetic genealogical DNA analysis and searching. The law defines FGG profiles, direct-to-consumer genetic genealogy services, and forensic genetic genealogical DNA analysis and search.
Maryland's framework requires judicial authorization and establishes statutory criteria, process requirements, restrictions, and safeguards for qualifying searches. The Maryland General Assembly continued considering amendments to the affidavit requirements in 2026, demonstrating that this regulatory model remains active rather than static.
18. Utah Regulates Investigative Genetic Genealogy by Statute
Utah has enacted statutory requirements governing investigative genetic genealogy, qualifying cases, database utilization, third-party DNA samples, law-enforcement and prosecutorial consultation, confirmatory testing, retention, destruction, and reporting.
Utah's framework reflects several principles that should be considered even where not legally mandatory: use FGG only in qualifying matters, search conventional forensic systems first when appropriate, require additional investigation before arrest, confirm the genetic hypothesis, and control retention and destruction.
19. Evidence, Discovery, and Disclosure
FGG investigations can generate an unusually large chain of scientific, genealogical, vendor, database, documentary, and investigative material.
| Record | Why It Matters |
|---|---|
| Original forensic sample records | Establish source, collection, chain of custody, condition, quantity, mixtures, and prior testing. |
| Traditional forensic testing | Documents STR development, CODIS eligibility, searches, exclusions, and why FGG was considered. |
| SNP laboratory records | Show laboratory method, quality metrics, contamination controls, profile generation, limitations, and accreditation. |
| Genealogy-service records | Document database used, account configuration, search date, law-enforcement access rules, match information, and service response. |
| Genealogist work product | Shows family-tree construction, relationship hypotheses, sources, alternatives, exclusions, and analytical steps. |
| Third-party reference samples | Consent, collection method, purpose, testing, retention, and destruction may become material. |
| Candidate-investigation records | Explain how investigators moved from a family branch to a particular candidate using non-genetic evidence. |
| Discarded DNA collection | Documents surveillance, abandonment, collection, chain of custody, contamination controls, and scope of analysis. |
| Confirmatory DNA | Provides the conventional forensic comparison supporting inclusion or exclusion. |
| Vendor communications | May reveal methods, limitations, investigative recommendations, database practices, or material changes in interpretation. |
20. Governance Framework for Agencies Using FGG
Define qualifying crimes, unidentified-remains cases, exhaustion requirements, sample quality, and circumstances permitting exceptions.
Require prosecutor consultation before testing or database search, particularly where statutory or constitutional questions are unsettled.
Identify when a warrant, court order, judicial authorization, consent, or other process is required by state law or provider rules.
Establish qualifications, accreditation, validation, contamination controls, profile quality thresholds, and documentation requirements.
Preserve and comply with the terms, notices, opt-in rules, privacy settings, and law-enforcement restrictions in effect at the time of the search.
Define training, documentation, conflict checks, peer review, source citation, and quality-control expectations for genealogy work.
Limit collection, review, disclosure, and retention of information concerning relatives who are not investigative targets.
Require independent forensic confirmation before treating a genealogy candidate as the biological source of crime-scene evidence.
Do not permit arrest based solely on a genealogy association; require independent probable-cause development.
Address forensic SNP profiles, third-party reference samples, database accounts, vendor copies, work product, and post-case disposition.
Establish how genealogy, laboratory, database, vendor, and confirmatory materials are preserved and provided to prosecutors.
Track searches, qualifying offenses, approvals, leads, identifications, arrests, exonerations, costs, errors, and complaints.
21. Questions Every Agency Should Answer Before Using FGG
22. What Comes Next
States are likely to continue defining qualifying cases, judicial authorization, database access, third-party sampling, reporting, and destruction requirements.
Congress and DOJ continue examining grant standards, laboratory requirements, privacy safeguards, reporting, and formal rules for FGG.
Improved sequencing may allow usable genealogy profiles from older, smaller, degraded, or otherwise challenging forensic samples.
Appellate courts will increasingly confront questions about SNP analysis, database searches, relatives' privacy, discarded DNA, warrants, and remedies.
Consumer genealogy companies may continue modifying law-enforcement access rules, opt-in settings, legal-process requirements, and privacy controls.
Genetic genealogy may increasingly be used not only to identify suspects but also to identify alternative perpetrators or assist innocence investigations.
23. Key Terms
24. Related ShieldPST.ai Resources
Place DNA, voice, gait, iris, fingerprint, and other biometric technologies within broader identification, privacy, evidence, and governance frameworks.
Open explainer →Compare genealogy databases with other privately operated data ecosystems accessed for investigative purposes.
Open explainer →Apply preservation, access control, audit, retention, and discovery principles to complex genetic and genealogy records.
Browse explainers →Genealogical investigations often rely on public-source records and online information to corroborate family relationships and candidate identities.
Open explainer →Connect genetic genealogy to privacy, Fourth Amendment, evidence, vendor management, procurement, policy, and oversight.
Open resource →Return to the Shield Technology Reference Library.
Browse explainers →25. Selected Authoritative and Primary Sources
Federal framework addressing eligibility, CODIS exhaustion, genealogy-service use, laboratories, third-party samples, investigative confirmation, privacy, retention, limitations, and oversight.
Review DOJ interim policy
DOJ explanation of how FGG differs from traditional CODIS searching and how genealogical matching is used to generate investigative leads.
Review DOJ announcement
Fourth Amendment decision addressing DNA collection by cheek swab from qualifying arrestees and identification-focused CODIS analysis under Maryland law.
Review Maryland v. King
Decision arising from an FGG investigation; holds that identification-focused STR analysis of DNA taken from a discarded napkin was not a search on the record presented, while expressly declining to decide privacy issues associated with the earlier SNP/genealogy analysis.
Review State v. Westrom
Supreme Court docket reflecting denial of certiorari on October 21, 2024.
Review Supreme Court docket
Detailed Maryland statutory framework defining FGG and establishing judicial authorization, eligibility, process, privacy, and related safeguards.
Review Maryland statute
2026 legislation proposing changes to affidavit requirements for judicial authorization of forensic genetic genealogical DNA analysis and searching.
Review Maryland 2026 legislation
Utah framework addressing qualifying cases, investigative genetic genealogy services, database utilization, third-party DNA, confirmatory analysis, retention, destruction, and agency reporting.
Review Utah legislation
Criminal case describing an investigation in which SNP testing and GEDmatch were used to generate a family tree and investigative leads, followed by conventional DNA evidence.
Review State v. Sharpe
26. Key Takeaways
- Forensic genetic genealogy is a lead-generation technique that combines dense forensic genetic profiling with genealogy databases and documentary family-tree research.
- FGG is materially different from traditional CODIS searching in marker density, database environment, purpose, relationship inference, and privacy impact.
- The best practice is to use appropriate conventional forensic methods first and reserve FGG for qualifying cases where ordinary identification methods have failed.
- Genealogy databases have different law-enforcement rules, and those rules can change. Agencies should preserve and comply with the terms in effect when a search occurs.
- A genetic association with a relative does not identify the perpetrator. It identifies a family relationship that must be investigated.
- Family-tree construction involves analytical judgment and should be documented with the same care as other significant investigative analysis.
- Third-party DNA samples raise consent and relational-privacy issues because one person's genetics reveals information about relatives.
- Discarded-DNA collection and genetic analysis are distinct legal steps; agencies should consult controlling jurisdictional law before treating abandonment as a complete answer.
- Candidate identity should be independently confirmed through conventional forensic DNA comparison before investigators characterize the person as the source of crime-scene DNA.
- Maryland v. King did not decide the constitutionality of forensic genetic genealogy.
- State v. Westrom likewise did not categorically approve SNP genealogy searching; its appellate holding focused on later identification-only STR analysis of discarded DNA.
- Maryland and Utah demonstrate the movement toward statutory controls governing case eligibility, judicial or prosecutorial review, database access, confirmation, retention, and reporting.
- FGG investigations may generate discoverable material far beyond the final STR report, including laboratory data, match information, genealogy work product, vendor communications, family trees, third-party samples, and candidate-narrowing records.
- The governing principle should be: genealogy can point investigators toward a person, but ordinary investigation and validated forensic evidence must establish whether that person belongs in the case.