In the previous post, I mentioned familial DNA. It is used in California where Virginia Brooks was murdered in 1931. So, would it be possible to collect DNA from a gunnysack or garments in evidence since 1931? Hopefully still in evidence. This is what the FBI has to say about it.

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 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.

Familial searching is not currently conducted at the national level or performed by the National DNA Index System [see Federal Register Vol. 73, No. 238 (December 10, 2008, at page 74937)]. To evaluate the feasibility of familial searching at the national level, the FBI’s CODIS Unit sought input from the Scientific Working Group on DNA Analysis Methods (SWGDAM) on specific questions relating to the efficiency of kinship matching compared to counting shared alleles, false positives and optimal database size, and optimal number of ranked candidates for the 10 million DNA profile database. SWGDAM provided the CODIS Unit with the following recommendations: (1) the use of kinship LRs is the preferred method for familial searching; (2) ranked lists should be reviewed since the true relative is not always ranked as the #1 candidate, and additional filters should be used to reduce the number of false positives; and, (3) since it is difficult to establish a threshold ranking for review of a ranked list when searching a database of over 10 million records when additional filters of metadata, geography, and Y-STR testing may not be available, routine familial searching at the national level is not recommended at this time.[2]


It is more important if more children were murdered by the same murderer(s) in later years, like the Everett sisters and their friend Jeanette in 1937.


Familial Searching (FBI)
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