Investigators and prosecutors should confirm that the DNA of a suspect identified through the familial-searching process exactly matches the DNA left by the alleged perpetrator. A familial DNA search result is only a lead that is then followed up and investigated until a DNA sample of the suspect is obtained and tested.

Familial searching is used to generate investigative leads, not to establish that a suspect is the source of the crime scene DNA. Under confirmatory procedures, once a candidate is identified, investigators must obtain a sample from the suspect and compare it directly to the crime-scene profile; if there is no direct match, the suspect is excluded.

“If a suspect is identified after a genetic association has occurred, STR DNA typing must be performed, and the suspect’s STR DNA profile must be directly compared to the forensic profile previously uploaded to CODIS. This comparison is necessary to confirm that the forensic sample could have originated from the suspect.” The policy describes this step under “Post-FGG Investigative Testing” as a requirement before relying on FGG leads in a case, but it does not state that such confirmatory testing is a universal legal prerequisite for making an arrest in all jurisdictions or all types of DNA-based identifications.

Once a suspect is identified via investigative genetic genealogy and relevant police work, confirmatory testing must be done using direct STR profile matching. Confirmatory matching requires a direct match between the suspect's and forensic sample's STR profile data; failure of that match means the suspect is excluded from further investigation.

Summarizing the DOJ policy, the site notes that the interim policy "establishes general principles for the use of FGGS by Department components" and that it applies when DOJ agencies or federally funded investigations use forensic genetic genealogy. It explains that the policy provides guidance on how FGG is used to generate investigative leads but that it “does not control investigative, scientific, or prosecutorial activities or decisions not specifically addressed,” indicating that it is not a comprehensive federal rule governing when arrests may occur in every DNA-based case.

In guidance about using federal grant funds, BJA states: “Effective in FY 2020, award recipients utilizing grant funds for forensic genealogy testing must adhere to the United States Department of Justice (DOJ) Interim Policy on Forensic Genetic Genealogical DNA Analysis and Searching (FGGS).” It adds that funds may be used for “investigative activities associated with the location, collection, and analysis of suspect DNA samples for comparison/identification of the actual perpetrator.” This reinforces that, under DOJ grant conditions, investigators are expected to collect and test a suspect’s own DNA to confirm FGG leads, but it frames this as a condition of funding and investigative best practice, not as a universal legal requirement before any arrest.

Describing U.S. federal practice, the article states: “Once a possible identity of the unknown has been reached, as per the US DOJ interim policy, a reference DNA sample of the potential candidate must be collected, forensic STR profiled, and compared to the original forensic profile, prior to any arrests being made.” It continues: “Reference DNA samples are collected by the law enforcement agency by requesting a sample from the candidate, or through surreptitious DNA collection, subject to all legal requirements for such collection. The resulting reference STR profile comparison to the forensic unknown will either confirm or refute the findings of the FGG investigation.” This explains that, under DOJ’s interim policy for FGG, investigators are expected to obtain and test the suspect’s own DNA to confirm a match before an arrest based on an FGG lead, but it is describing DOJ policy for FGG cases, not a general nationwide legal rule for all familial DNA searching.

The DOJ press release explains that forensic genetic genealogy "provides an alternative option" when CODIS searches fail, and that it is used to “generate a lead.” It states that the Interim Policy “provides the first comprehensive guidance to law enforcement on the use of FGG” and that it outlines “how the practice is used to generate leads for unsolved crimes.” It emphasizes that FGG is a lead‑generation tool, while traditional forensic DNA comparison is still needed to make an evidentiary match, but the release does not separately articulate a generally applicable legal rule that an arrest cannot occur until a suspect’s DNA has been obtained and tested in every case involving familial DNA searching.

State laws in many jurisdictions require DNA collection after arrest for specified offenses. For example, Virginia law states that all persons arrested for a felony offense shall have a DNA sample drawn or taken at the time of booking or as soon as practicable after arrest.

In discussing the DOJ policy, the article notes that “the 2019 Department of Justice FGGS interim guidelines” require that, after a genetic association is developed, “investigators must obtain a reference sample from the suspect and conduct STR testing to directly compare with the crime‑scene profile before making an arrest based on that lead.” The article also observes that these guidelines are internal policy for federal cases and grant‑funded investigations, and that “state and local agencies not using federal resources are not directly bound by the DOJ interim policy,” though many may voluntarily follow it as a best practice.

The editorial explains: “The 2019 DOJ interim policy provides guidance on the use of FGG in criminal investigations. Importantly, the policy primarily applies to cases investigated by federal law enforcement agencies, cases funded by federal grants (including grants passed through to state, local, or tribal agencies), and cases where DOJ personnel, contractors, or grantees are directly involved in the process.” It notes that the policy “does not directly regulate state or local cases that are funded by non‑federal sources; however, many agencies look to the DOJ policy guidelines as a national standard,” indicating that while DOJ policy may call for confirmatory STR testing of a suspect’s DNA before arrest in FGG cases, that requirement is policy‑based and not automatically binding on all non‑federal investigators using familial or genealogical DNA techniques.

Surveying Illinois practice, the article describes the administrative framework for familial searches: “A prerequisite to initiating a familial search starts with the completion of a ‘Memo of Understanding’ (MOU) that must be signed by…” and then outlines conditions for using familial DNA in investigations. It also discusses the Illinois DNA Database Law, explaining that it “allows the Illinois State Police to obtain samples of biological material from those in custody” and mandates submission for certain categories. The focus is on when familial searches can be used and how DNA can be collected from people already in custody; the article does not identify any Illinois statute or rule that categorically requires police to obtain and test a suspect’s DNA and confirm an exact match to the crime scene sample as a *legal prerequisite* to arresting the suspect.

The Maryland Act requires judicial authorization before initiating a forensic genetic genealogical search. It also requires that the forensic sample satisfy specific criteria and that law enforcement use the method only after state and national databases have been tested without success.

Surveying state practices on familial DNA searching, the article explains that many state policies treat familial DNA hits as investigative leads that must be corroborated. It notes that jurisdictions such as California and Colorado require additional investigative work and often direct comparison of the suspect’s DNA profile with the crime‑scene profile before prosecution, but “the specific procedural requirements, including whether a confirmed STR match is obtained before arrest, vary by jurisdiction and are usually set by state laboratory policies or memoranda, not by a uniform national rule.” This indicates that while confirmatory suspect testing is common practice and often required by policy, it is not universally mandated in the same way everywhere.

Britannica explains that DNA profiling is used to compare biological samples and identify possible matches, but a match from an indirect or partial comparison is not the same as a direct identification of a specific individual. This supports the distinction between a familial lead and confirmatory testing.

The abstract says familial DNA analysis yields valuable investigative insights when a reference sample is absent and involves stricter criteria than standard DNA testing. It notes that high-stringency matching requires exact profile matches, reinforcing that familial searching is not itself an exact-match determination.

Under existing New York regulations, a familial search may be used only when there is a partial match between the crime-scene profile and a stored offender profile. Practically, familial searching is used only after a comparison of the forensic DNA profile with known offender or arrestee profiles has not identified any match.

Unless and until it is determined that a suspect's DNA profile matches the single-source forensic sample recovered from the crime scene, law enforcement may only interview a suspect identified by familial DNA testing if the suspect is first told that the partial match is not conclusive proof that the crime-scene DNA belongs to the suspect.

This article argues against a categorical constitutional or statutory rule requiring probable cause for law enforcement to conduct familial DNA searches. It also argues against a ban on familial DNA searches in police or consumer databases.

In practice, a familial DNA hit is typically treated as an investigative lead, not probable cause by itself. Investigators usually obtain a reference sample from the suspect and compare it to the crime-scene profile before making a charging or arrest decision, but there is no universal legal rule requiring a confirmed exact DNA match before arrest in every jurisdiction.

A user quoting from the DOJ Interim Policy writes: “If a suspect is identified after a genetic association has occurred, STR DNA typing must be performed, and the suspect’s STR DNA profile must be directly compared to the forensic profile previously uploaded to CODIS. This comparison is necessary to confirm that the forensic sample could have originated from the suspect.” The commenter interprets this to mean that law enforcement should “use genetic genealogy to find the suspect, then get the suspect's DNA and compare to the DNA in evidence,” and notes that FGG is a tool to try to find a suspect but “is not ‘evidence’ that can support a prosecution” without a direct DNA comparison.