Familial Searching – An Interview with Rock Harmon

Familial Searching has been getting a lot of attention lately, and for good reason. In the fight against crime, it is essential that law enforcement is able to use all of the tools at their disposal. In the United Kingdom, Familial Searching has been used since 2003 to help solve approximately 40 serious crimes (as of May 2011). If you’re considering implementing Familial Searching in your jurisdiction, I encourage you to read the Familial DNA Searching: Current Approaches Report published by the Forensic Technology Center of Excellence.

In order to learn more about Familial Searching, I sat down with Rock Harmon, retired Senior Deputy District Attorney for Alameda County, California after 33 years. Currently, Rock is employed as a consultant to numerous law enforcement agencies dealing with such issues as cold case investigation and other issues related to forensic DNA typing.



WRITTEN BY: Tara Luther, Promega




What is familial DNA search? When was it developed/first used?

Familial searching (FS) is an additional search of a DNA profile in a law enforcement DNA database that is conducted after a routine search fails to identify any profile matches. The FS process attempts to provide investigative leads to agencies engaged in the pursuit of justice by identifying a close biological relative of the source of the unknown forensic profile obtained from crime scene evidence. FS is based on the concept that first‐order relatives, such as a sibling or parent/offspring, often will have more alleles of their DNA profiles in common than those of unrelated individuals.


In brief, how does it work?

Familial Searching is based on the concept that first-order relatives—such as a sibling or parent/offspring— often will have more alleles of their DNA profiles in common than those of unrelated individuals. FS involves a two‐phase process. The first phase of FS produces a candidate list from the DNA database ranked by likelihood ratio estimates supporting the specified relationship (i.e., parent– offspring and full sibling) compared with the alternate hypothesis of being unrelated. The second phase of the process typically uses additional genetic testing, such as analysis with lineage markers, usually Y‐ STRs, to confirm or refute the specified relatedness.


In what types of cases is familial DNA search most appropriate and effective?

Familial Searching is suitable for use to try to produce investigative leads from biological evidence in any unsolved crime where that evidence is material. It is typically used for unsolved rapes and murders after the evidence profile has been uploaded to CODIS and no offender hit has been produced.


What states are currently using the technique?

Virginia, Colorado, Texas, California, Wyoming, Utah, Minnesota, Florida, Michigan


Have these states demonstrated success?

Yes, to varying degrees. An effort was made to calculate a success metric for Familial Searching using the same criteria that the FBI uses to calculate the effectiveness of CODIS. Of the 90 FS cases in Denver to date, 23 of the database searches resulted in identification of a true biological relative of the evidentiary sample (a success rate of approximately 26%). California’s success metric is 26/66, or 39%. This data suggests that FS can be at least as successful as CODIS is.


What are the legal limitations/ramifications?

There are none once it is determined that the existing state database law implicitly authorizes Familial Searching as all nine states have determined. There are no changes to anyone’s 4th Amendment rights inherent in FS.


What concerns may be preventing or slowing its use in the field?

Misconceptions and confusion abound! Questions about statutory interpretation are answered by scientists, not lawyers. Whether or not legislative changes are necessary are the principal subject of confusion. The fact that every state using FS found authorization in their existing database law is either unknown or of little concern.

Perhaps the biggest obstacle to FS is the shocking underutilization of Y-strs in about half of the government labs in the US. While this inadequacy denies a valuable tool from law enforcement in those jurisdictions, its absence also dooms any future for FS because the Y-str lineage testing is a vital major component of FS.


One could expect Familial Searching might produce investigative leads in 84,760 cases. Share on X


Are there ways to overcome these concerns?

Open, meaningful discussion among the labs, law enforcement, and knowledgeable prosecutors can easily inform and address any concerns.


What are the ramifications for law enforcement not being able to use Familial Searching to solve crimes in their jurisdictions?

Currently, there are approximately 326,000 unidentified forensic profiles in NDIS that have not been associated with aiding an investigation. If the success rate of FS is maintained at the same rate as that in Denver (26%), then one could expect FS to produce valuable investigative leads in about 84,760 additional cases.

Instead law enforcement has been turning to highly unproductive practices such as DNA dragnets, genealogy, pictures from DNA, and bio-ancestry information instead of having meaningful discussions about implementing FS.


What do you see for the future of familial DNA search?

While the potential of Familial Searching has been demonstrated, interest in adopting FS appears to be waning.



Rockne Harmon graduated from the United States Naval Academy in 1967 and served four years active duty.  He served a combat tour in Vietnam as Officer in Charge of a Navy Swift Boat and received the Purple Heart for wounds received in combat.  After his military service he attended the University of San Francisco School of Law and graduated in 1974.  He is a Fellow of the American Academy of Forensic Sciences.

He was the prosecutor in a triple murder case that established the general acceptance of conventional serological methods, the precursor to today’s DNA technology.( People v. Lawrence Reilly).  As a result of that case he was in a position to assist the forensic science community as it began the implementation of DNA typing soon thereafter.

He has written and lectured extensively on the subject of the admissibility of forensic evidence, particularly DNA evidence. In 1998 he received an award from the FBI Director for his efforts supporting the FBI in their first decade of DNA typing.   In 2003 he received the Achievement Award from the International Homicide Investigators’ Association for his work on cold cases.

He was the Chairman of the California District Attorneys’ Association Forensic Science Committee and was on the Advisory Board to the International Homicide Investigators’ Association for many years.   At Alameda County he developed a highly successful protocol for solving old or unsolved cases using DNA typing.  He was the driving force behind the California Attorney General’s decision to implement familial DNA searching in California that led to the arrest of the “Grim Sleeper” serial killer in 2010.

He was one of the prosecutors in People v. O. J. Simpson.