Cover: Forensic Familial and Moderate Stringency DNA Searches

Forensic Familial and Moderate Stringency DNA Searches

Policies and Practices in the United States, England, and Wales

Published Aug 12, 2019

by Tepring Piquado, Carl F. Matthies, Lucy Strang, James M. Anderson

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Research Questions

  1. What are the characteristics and quality of DNA samples collected in the United States?
  2. What is the typical process for familial or moderate stringency searching and partial-match reporting in the United States?
  3. How often are familial and moderate stringency searches conducted in the United States?
  4. Can the history and practice in England and Wales inform decisionmaking for policymakers in the United States?

Forensic DNA testing has helped law enforcement solve crimes, often long after the investigative trail has gone cold. Familial DNA and moderate stringency search protocols are logical extensions for cases where there is no exact DNA match. Although familial DNA searching is permissible in most states, it is used sparingly. Additionally, policies governing the use of familial searching lack consistency, and lawmakers might be uncertain about the procedure's effectiveness in solving or deterring crime — and about the unintended implications and legal, ethical, and practical barriers to its wider adoption.

The authors provide a baseline for criminal justice policymakers to better understand the ways in which familial DNA and moderate stringency testing are being used in the field today. Their findings are based on a U.S. survey and study of practices at state and local forensic laboratories and interviews with representatives of two states — California and Texas — that have used the technique in different ways. Additional qualitative interviews shed light on how the issues of privacy, public safety, and budget consciousness have shaped policies on familial DNA searching in England and Wales. The authors fill a knowledge gap for academics and practitioners about the history, prevalence, and typical practice of this technique and for policymakers seeking to make informed decisions on whether an expansion of the U.S. DNA databases would be acceptable by society in investigating how crimes can potentially be solved or prevented.

Key Findings

  • Familial DNA searching and the expanded use of genetic-based investigation raise difficult legal, ethical, and policy concerns.
  • Although familial searching is permissible in many states, it is used sparingly.
  • California and Texas, the two largest states by population, also have the two largest state-level DNA databanks, but they restrict the use of familial DNA testing to situations that justify its use and where the public safety implications are most acute. As of 2018, these two states combined had approved and conducted fewer than 100 familial searches.
  • Familial and moderate stringency DNA searches effectively increase the number of individuals to investigate because they include individuals who have not been convicted, arrested, or even suspected of committing a crime, which raises important concerns about intrusiveness and privacy. Known racial disparities in the criminal justice system might result in racially biased genetic population surveillance.
  • Continual advancements in forensic DNA testing suggest that familial searching at these laboratories may be replaced by more-powerful alternatives in the future.
  • Local labs want to see improvements in the Code DNA Index System software to facilitate data queries and production of statistical reports.
  • It is unclear whether familial or moderate stringency searches are more cost-effective overall than the status quo.


  • Because accountability and transparency are essential for public confidence in law enforcement, greater efforts are needed to obtain reliable statistics from the different U.S. databases. Implementing standardized reporting formats across all the databases would better inform research and lead to better insight into the efficacy of familial and moderate stringency DNA searching and the reporting of partial match results.
  • Following the example set in England and Wales, the United States could benefit from publishing annual reports with information about the methodology used, the number of searches done each year, and the match rates. For the future improvement of policies, this information should be made publicly available online.
  • Further research is also needed to collect more detailed information on the direct and indirect costs of familial and moderate stringency DNA searching — including the upfront investment in software, unit costs for laboratory materials, and labor costs. Policymakers would then have an evidence-based cost analysis for making better decisions about the most efficient crime reduction expenditures.

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The research described in this report was sponsored by the National Institute of Justice and conducted in the Justice Policy Program within RAND Social and Economic Well-Being.

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