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Familial Searching

Familial searching is an additional search of a law enforcement DNA database conducted after a routine search has been completed and no profile matches are identified during the process.

Familial Searching

Familial searching is an additional search of a law enforcement DNA database conducted after a routine search has been completed and no profile matches are identified during the process.  Unlike a routine database search which may spontaneously yield partial match profiles, familial searching is a deliberate search of a DNA database conducted for the intended purpose of potentially identifying close biological relatives to the unknown forensic profile obtained from crime scene evidence.  Familial searching is based on the concept that first-order relatives, such as siblings or parent/child relationships, will have more genetic data in common than unrelated individuals.  Practically speaking, familial searching would only be performed if the comparison of the forensic DNA profile with the known offender/arrestee DNA profiles has not identified any matches to any of the offenders/arrestees.  

Familial searching is often confused with what occurs when a partial match results from the routine search of the DNA database.  A partial match is the spontaneous product of a regular database search where a candidate offender profile is identified as not being identical to the forensic profile but because of a similarity in the number of alleles shared between the two profiles, the offender may be a close biological relative of the source of the forensic profile.

While familial searching is now being performed in several jurisdictions in the United States, the United Kingdom (UK) has the most experience conducting familial searching of their National DNA Database.  Since 2003, the UK has conducted approximately 200 familial searches resulting in investigative information used to help solve approximately 40 serious crimes (as of May 2011).  The UK has developed detailed protocols for familial searches that include an approval process, considerations for prioritization, research of family history, and training of law enforcement officers.  One of the key components responsible for the effectiveness of the UK’s system is that the search is not based upon genetics alone.  Age, and more importantly, geographic location, are combined with the genetic data to produce a ranked list of potential relatives of the unknown forensic profile.

In considering whether familial searching should be implemented in your jurisdiction, it is important to recognize that a relative must already be in the database in order for the search to identify them as a potential relative of the forensic profile.  It should be noted that even if a relative is in the database, it is possible that the relative may not be included in the ranked list produced by the familial search.  For example, California’s validation of their familial searching protocol showed that approximately 93% of fathers and 61% of full siblings were identified by their familial search procedure using the CODIS 13 core loci in searching a database of approximately one million DNA profiles (96% of fathers and 72 % of full siblings were identified using 15 loci) [1].  However, regardless of whether or not a relative is in the database, a familial search will always generate a ranked list of potential candidates for evaluation. 

Is familial searching currently conducted at the national level?  No, familial searching is not currently performed at the National DNA Index System.  See Federal Register Vol. 73, No. 238 (December 10, 2008 at page 74937). 

What States perform familial searching?  As of June 2011, California, Colorado, Texas and Virginia perform familial searching.

Can familial searching help to solve some cases?  Yes, when applied properly.  There are several considerations States should take into account when evaluating whether to move forward with familial searching within their state.

Discussion Topics for States Considering Familial Searching:


  • Consider the applicable state laws and regulations governing the DNA databasing program to determine the best legal approach.  Because many of the State laws are silent on the issue of familial searching, it is important to have a full legal review to evaluate whether familial searching is authorized in your jurisdiction.  Those states which have adopted or rejected familial searching have done so under a variety of authorities:
    • California implemented its familial search program with the approval of their Attorney General.  Several other states have recently introduced legislation (currently still in committee): Minnesota, Pennsylvania, and Tennessee.  Two jurisdictions currently prohibit, by law, the use of familial searching; Maryland and the District of Columbia.  Other jurisdictions have implemented familial searching based upon laboratory policy.


  • Staff
    • Implementation of a successful familial search program takes time and requires significant resources and staff.  Personnel with an expertise in kinship comparisons are necessary. 
    • Consider forming a Task Force to review requests for familial searches as well as evaluating any familial search results.  Such a Task Force should include laboratory personnel as well as law enforcement personnel with access to criminal history records for researching background information on potential linkages. 
  • Software
    • The current version of CODIS software does not have the capability to efficiently search and return information for familial searching.  The states that conduct familial DNA searches use specially designed software (not CODIS) to conduct these searches.
    • As with implementation of any new software, validation is required before use of such software in laboratory operations.  Any validation must be conducted in accordance with Standard 8 of the FBI’s Quality Assurance Standards. 
    • Develop Standard Operating Protocols for familial searching before implementing a familial search program.
  • Policies and Procedures
    • Policies and procedures regarding familial searching should be approved prior to implementation.  Policies and procedures should address, at a minimum, the following topics:
      • Privacy Considerations
      • Release of information
      • Process for approval of search requests (Board decision, Laboratory management, etc)
      • Types of crimes eligible and other criteria for familial searching
      • Frequency of searches
      • Use of additional genetic testing (e.g. YSTR) to narrow search results
      • Reporting of search results
      • Categories searched (offenders only, offenders and arrestees, etc.)

Training for Law Enforcement

1 S.P. Myers, et al., Searching for first-degree familial relationships in California’s offender DNA database: Validation of a likelihood ratio-based approach, Forensic Sci. Int. Genet. (2010).