DNA Testing

Biometrics and Fingerprints

The Combined DNA Index System, or CODIS, blends forensic science and computer technology into a tool that enables federal, state, and local forensic laboratories to exchange and compare DNA profiles electronically, thereby linking serial violent crimes to each other and to known offenders. Using the National DNA Index System of CODIS, the National Missing Persons DNA Database also helps identify missing and unidentified individuals.

CODIS generates investigative leads in cases where biological evidence is recovered from the crime scene. Matches made among profiles in the Forensic Index can link crime scenes together, possibly identifying serial offenders. Based upon a match, police from multiple jurisdictions can coordinate their respective investigations and share the leads they developed independently. Matches made between the Forensic and Offender Indexes provide investigators with the identity of suspected perpetrators. Since names and other personally identifiable information are not stored at NDIS, qualified DNA analysts in the laboratories sharing matching profiles contact each other to confirm the candidate match.

The FBI Laboratory’s CODIS began as a pilot software project in 1990, serving 14 state and local laboratories. The DNA Identification Act of 1994 formalized the FBI’s authority to establish a National DNA Index System (NDIS) for law enforcement purposes. Today, over 190 public law enforcement laboratories participate in NDIS across the United States. Internationally, more than 90 law enforcement laboratories in over 50 countries use the CODIS software for their own database initiatives.

Through the combination of increased federal funding and expanded database laws, such as the DNA Fingerprint Act of 2005, the number of profiles in NDIS has and will continue to dramatically increase, resulting in a need to re-architect the CODIS software. A considerable focus during this time will be to enhance kinship analysis software for use in identifying missing persons. This next generation of CODIS will utilize STR and mtDNA information, as well as metadata (such as sex, date of last sighting, age, etc.) to help in the identification of missing persons. The re-architecture will also enable CODIS to include additional DNA technologies, such as Y-Short Tandem Repeat (Y-STR) and mini-Short Tandem Repeat (miniSTR).

The FBI Laboratory is committed to the support of the CODIS program. With the continued cooperation and collaboration of legislative bodies and all components of the criminal justice community—law enforcement, crime laboratories, victims, prosecutors, and the judiciary—the future of DNA, CODIS, and NDIS holds even greater promise to solve crime and identify missing persons.


The CODIS Unit—made up of program managers, forensics system program managers, biologists, auditors, management and program analysts, and paralegal specialists—manages CODIS and NDIS.

The unit is responsible for developing, providing, and supporting the CODIS program to federal, state, and local crime laboratories in the United States and selected international law enforcement crime laboratories to foster the exchange and comparison of forensic DNA evidence from violent crime investigations. The CODIS Unit also provides administrative management and support to the FBI for various advisory boards, Department of Justice grant programs, and legislation regarding DNA.

Quality Assurance 

The DNA Identification Act of 1994 required the formation of a panel of distinguished professionals, from the public and private sectors, to address issues relevant to forensic DNA applications. This panel, the DNA Advisory Board (DAB), first convened in 1995. An early mission of the DAB was to develop and implement quality assurance standards for use by forensic DNA testing laboratories. The scope was quickly expanded to include forensic DNA databasing laboratories, as well. The DAB fulfilled this role, recommending separate documents detailing quality assurance standards for both applications.

The Quality Assurance Standards for Forensic DNA Testing Laboratories and the Quality Assurance Standards for DNA Databasing Laboratories were first issued by the Director of the FBI in October 1998 and April 1999, respectively. Both documents have become benchmarks for assessing the quality practices and performances of DNA laboratories throughout the country. When the DAB’s statutory term expired, it transferred responsibility for recommending revisions of these quality assurance standards to the Scientific Working Group on DNA Analysis Methods (SWGDAM).

The DNA Identification Act of 1994 also required that the FBI Laboratory ensure all DNA laboratories that are federally operated, receive federal funds, or participate in the National DNA Index System (NDIS) demonstrate compliance with the standards issued by the FBI. Typically, documentation of a laboratory’s compliance with a stated standard has been measured through an audit process. Such audits have been performed by forensic scientists, either internal or external to the laboratory, and serve to identify compliance with established standards.

Active with the July 2020 audit documents and for audits conducted in accordance with the quality assurance standards (QAS) effective July 1, 2020, audit guidance can be located in the QAS guidance document.

Please direct questions regarding training for the quality assurance standards to QAS@fbi.gov

Planned Process and Timeline for Implementation of Additional CODIS Core Loci 

Coinciding with the revision of the FBI Director’s Quality Assurance Standards and an examination of the procedures for operation of the National DNA Index System (NDIS), the FBI Laboratory impaneled a CODIS Core Loci Working Group in May 2010 to evaluate the necessity for additional loci. Almost 12 years earlier, the FBI’s original STR Standardization Project had recommended the 13 CODIS core loci required (and still being used) for DNA data uploaded to NDIS. Despite the different environments in which the original STR Project and the current working group were and are operating, both recognized the importance of balancing the privacy issues attendant to storing genetic information with ensuring the effectiveness of CODIS to assist criminal investigations. Among its first tasks, the current working group recommended criteria for acceptance of any new CODIS loci, including no known association to medical conditions or defects (this refers to whether or not the loci is diagnostic of any known medical condition or disease status).1

In a letter to the editor of Forensic Science International Genetics announcing the proposed additional loci under consideration for CODIS, the working group identified the following three factors in support of expanding the current CODIS core loci: 1) facilitates greater discrimination, 2) assists in missing person investigations, and 3) encourages international data sharing efforts by having more loci in common with other countries for comparison purposes.2 The chairperson of the working group updated the DNA community on the selection of the potential additional CODIS core loci at the 22nd International Symposium on Human Identification, the 15th- 17th National CODIS Conferences, the European Network of Forensic Science Institutes’ 2011 DNA Working Group meetings, and the 2011 semiannual meetings of the Scientific Working Group on DNA Analysis Methods (SWGDAM). As the working group addressed the validation and implementation phases of the project, the attached process and timeline for determination of additional CODIS core loci were developed to keep the community apprised of the group’s progress and provide an outline for what remained to be accomplished. The working group held discussions with STR kit manufacturers (subject to non-disclosure agreements) on the development of STR kits that incorporate some or all of these proposed loci. Additionally, the working group identified the following statutory and operational requirements for adding new loci:

  • The Federal DNA Identification Act of 1994 [42 U.S.C. §14132] requires compliance with the quality assurance standards issued by the FBI Director. The Quality Assurance Standards for Forensic DNA Testing and DNA Databasing Laboratories define the minimum requirements for validation.
  • The Justice for All Act [Pub. Law 108-405 §203(f)] requires that the Department of Justice provide Congress with notice of the proposed use of new core markers 180 days in advance of any such implementation.
  • Operational Procedures for the National DNA Index System (NDIS) also contain minimum criteria for approval of additional loci or kits that will be acceptable at NDIS, such as concordant studies, mixed samples, non-probative samples, population studies, and precision studies.

Process for Determination of Additional CODIS Core Loci

Selection of laboratories to participate in validation studies:

  • Based upon recommendations from the CODIS Core Loci Working Group, the FBI will select laboratories representative of the forensic DNA community (i.e., casework, database, missing person, instrument platforms, kits, etc.), to participate in a validation project for the proposed CODIS core loci using criteria derived from the Quality Assurance Standards and NDIS Procedures.
    • Participating laboratories will be responsible for:
      • Management approval of participation agreement
      • Dedicated personnel for the length of the project
      • Instruments required for the validation
      • Samples for analysis
    • The FBI will be responsible for:
      • Costs of the STR kits used by participating laboratories
      • Definition and coordination of validation experiments, data evaluation, and assessment

Validation of proposed additional CODIS core loci:

  • Congress will be notified of the proposed additional CODIS core loci.
  • Participating laboratories will conduct validation experiments/studies in accordance with the Quality Assurance Standards.
  • Successful validation efforts will be dependent on as-yet-undetermined factors, such as:
    • Ability of kit manufacturers to make robust versions of kits available for purchase
    • Ability to include additional loci within existing 5-dye chemistry
    • Ability to configure existing instruments to run 6-dye chemistry
    • Separate validation tracks for casework and known database samples
    • Availability of federal funding
  • Compilation, review, and evaluation of validation results.
  • Feedback to kit manufacturers and incorporation of any resulting changes to kits in the validation plan.
  • Publication or posting of the validation results.
  • Ongoing progress reports to DNA community and other stakeholders.

Selection of CODIS core loci:

  • Input will be obtained from, and progress reports provided to, the DNA community and other stakeholders.
  • Assessment and selection of new CODIS core loci will be performed.

Implementation of new CODIS core loci into NDIS operations:

  • The DNA community will be involved in review and development of the following:
    • Ongoing progress reports
    • Sufficient lead time necessary for implementation
    • Searching Strategies
    • Match Strategies
    • Confirmation Strategies
  • Congress will be notified of the new CODIS core loci required for upload and searching at NDIS.

Twenty CODIS Core Loci 

In early 2015, the FBI announced that the validation project for additional CODIS core loci had been completed and that an additional seven loci would be added to the CODIS core loci effective January 1, 2017.3 

Along with the original 13 loci, these additional seven loci—D1S1656, D2S441, D2S1338, D10S1248, D12S391, D19S433, and D22S1045—now comprise the CODIS core loci.

20 CODIS core loci:

  • CSF1PO
  • D3S1358
  • D5S818
  • D7S820
  • D8S1179
  • D13S317
  • D16S539
  • D18S51
  • D21S11
  • FGA
  • TH01
  • TPOX
  • vWA
  • D1S1656 
  • D2S441 
  • D2S1338  
  • D10S1248  
  • D12S391 
  • D19S433 
  • D22S1045 

Updated Timeline for Determination of Additional CODIS Core Loci

Form a working group to discuss initial selection
Establishes target goals
  • CODIS Core Loci Working Group with FBI chair and five members
  • Web meetings
May 2010 to present
Announce proposed additional CODIS core loci
Sets desired target goals and informs manufacturers
  • Working group chair
  • Publish proposed listing of CODIS core loci
April 2011 online (published January 2012)
Ongoing progress reports
Provides updates for DNA community
  • Working group chair
  • Present updates on status of CODIS Core Loci project at meetings
2010 to 2012
Implementation considerations and strategy
Identify issues for implementation and timeline
Working group
June 2011 to present
Manufacturers develop prototype kits
Creates tools to meet target goals
  • Manufacturers
  • Provide status reports to working group for timeline
2011 to 2012
Test and validate prototype kits
Examines if target goals can be met
  • Validation laboratories
  • Follow QAS compliant validation plan
2013 to 2014
Review and evaluate data from validation
Evaluates if desired performance is obtained
  • Provide feedback, if any, to manufacturers
In conjunction with and at the conclusion of validation (2013 to 2014)
Selection of new CODIS core loci
Allows protocols to be established
  • FBI
  • Seek input from DNA community and stakeholders
  • Notify Congress
November/December 2014
Implementation of new CODIS core loci at the National DNA Index System
Enables target goals to be met
All NDIS-participating labs
January 1, 2017

Related Resources

  • CODIS Brochure: The FBI Laboratory’s Combined DNA Index System (CODIS) blends forensic science and computer technology into an effective tool for solving crime.
  • Notice of Release of the 2015 FBI Population Data for the Expanded CODIS Core STR Loci:The FBI Laboratory announced an expansion of the original 13 short tandem repeat (STR) loci that have been the core of NDIS since 1997. Seven additional STR loci have been selected and will be required for upload and searching of DNA profiles at NDIS effective January 1, 2017.

  • Notice of Amendment of the FBI’s STR Population Data Published in 1999:In response to new, commercially available amplification kits that expand the number of loci in a multiplex reaction, the FBI Laboratory has retyped certain population samples to establish allele distributions for the additional loci and is providing the amended allele frequency tables for use by anyone interested in performing comparisons with previously published data.
1 For the complete list of criteria, please refer to Expanding the CODIS Core Loci in the United States, D.R. Hares, Forensic Sci. Int. Genet. 6 (2012), e52-e54.
2 This formal notification of the additional loci proposed by the working group for consideration as CODIS core loci was announced in the April 2011 on-line edition of Forensic Science International (FSI) Genetics and published in the January 2012 edition of FSI Genetics (D.R. Hares, Forensic Sci. Int. Genet. 6 (2012), e52-e54). An addendum (in press) is available online (D.R. Hares, Addendum to expanding the CODIS core loci in the United States, Forensic Sci. Int. Genet. (2012), doi:10.1016/j.fsigen.2012.01.003).
3 Selection and implementation of expanded CODIS core loci in the United States, D.R. Hares, Forensic Sci. Int. Genetics 17:33-34 (2015).

Familial Searching 

Note: Familial searching is not conducted at the federal level. States considering familial searching can review discussion topics as a starting point.

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. From 2003 to 2011, the UK conducted approximately 200 familial searches resulting in investigative information used to help solve approximately 40 serious crimes. 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). 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.

It is important to note that familial searching differs from forensic genetic genealogy, also known as genealogical/ancestry searching, long-range familial searching, and investigative genealogy.

Forensic genetic genealogy is conducted on non-law enforcement DNA databases and uses different markers than the 20 CODIS law enforcement offender database markers.

This type of searching is most commonly used by individuals who voluntarily submit their DNA data to third-party companies in an attempt to find relatives or develop family trees.

In some cases, law enforcement agencies are using forensic genetic genealogy to find the perpetrators of violent crimes by trying to identify their relatives; this type of searching led to the positive identification of California's Golden State Killer in 2018.

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.

Discussion Topics for States Considering Familial Searching 

While familial searching is not performed at the national level, the following states currently perform familial searching: Arkansas, California, Colorado, Florida, Michigan, Texas, Utah, Virginia, Wisconsin, and Wyoming.

Familial searching can help solve certain cases when applied properly. States considering familial searching can review the discussion topics below as a starting point. Additionally, the “Recommendations from the SWGDAM Ad Hoc Working Group on Familial Searching” provide more information on this topic, including an appendix on their familial searching studies.


  • Consider the applicable state laws and regulations governing the DNA databasing program to determine the best legal approach. Because many 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:
    • Several states perform familial searching with the approval of state officials—for example, California implemented its familial search program with the approval of the state attorney general. Other jurisdictions have implemented familial searching based upon an administrative determination or laboratory policy. Two jurisdictions, Maryland and the District of Columbia, currently prohibit, by law, the use of familial searching.


  • 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 to evaluate the familial search results. Such a task force should include laboratory personnel as well as law enforcement personnel and/or prosecutors, who are authorized to access criminal history records for researching background information on potential candidates.
    • Because the results generated by familial searching are not the same as CODIS matches, it is important to train law enforcement personnel on the appropriate follow-up, including additional investigative work.
  • Software
    • 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 (SOPs) for familial searching prior to implementation of a familial search program.
  • Policies and procedures should be developed and approved prior to implementation and address, at a minimum, the following:
    • Privacy considerations
    • Release of information
    • Criteria for familial search requests:
      • Types of crimes eligible for searching
      • Types of forensic DNA records eligible for searching
      • If all other investigative leads must first be exhausted
      • Approval by task force, board, laboratory management, etc.
    • Processes for familial search:
      • Type of DNA records to be searched (e.g., offenders only, offenders and arrestees
      • Frequency of searches
    • Use of additional filters for search results (e.g., YSTR testing, metadata)
    • Reporting of search results

Missing Person Comparison Request 

The FBI administers the National Missing Person DNA Database (NMPDD) as part of the National DNA Index System (NDIS). The NMPDD compares DNA records stored in the Missing Person, Relatives of Missing Person, and Unidentified Human Remains Indexes of NDIS.

Sufficient DNA data from both the human remains and the relatives of the missing person are needed to produce a statistically significant database association involving DNA profiles in a missing persons case. To maximize the potential for such associations, as much genetic information as possible should be requested and obtained in a missing person investigation.

This may be accomplished by:

  • Collecting DNA samples from multiple relatives.
    • Any relative of the missing person offering to provide a DNA sample should have a sample collected. The laboratory will assist in determining which samples should be analyzed and databased.
  • Requesting mitochondrial DNA (mtDNA) analysis on at least one maternal relative for all missing person cases, regardless of gender.
  • Requesting Y-STR analysis on at least one paternal relative if the missing person is a male.
  • Requesting mtDNA analysis on all unidentified human remains and Y-STR analysis on male remains.

However, despite these efforts, when limited genetic information is available, associations may not be possible through database searches. Circumstances that may prevent a database association from occurring include:

  • The DNA data has not been uploaded to NMPDD/NDIS.
  • Insufficient STR results were obtained from the human remains.
  • The resulting DNA data contains a mtDNA or YSTR haplotype that is relatively common in the relevant population.
  • There is diminished allele sharing between relatives and remains when first-degree relatives (e.g., parents, offspring, or siblings) are not available to provide a sample.

If a law enforcement agency investigating a case believes that a particular set of remains may be those of a specific missing person, a request for a manual comparison may be warranted. A manual comparison is a direct comparison of the DNA data obtained from specific missing person-related records outside of the routine NMPDD searches. Known reference DNA records, such as offender and arrestee DNA records, are generally not subject to retrieval from CODIS for manual comparison purposes. Missing person reference DNA records, however, may be retrieved from DNA databases (CODIS) for manual comparison because these reference samples were obtained through a voluntary consent process and were contributed solely for the purpose of identifying a missing or unidentified person.

All requests for manual comparison shall be made by the investigating agency directly to the NDIS participating laboratory responsible for the missing person-related DNA records. Non-law enforcement agencies or organizations seeking manual comparisons should direct their requests to the appropriate investigating agency or medico-legal authority to ensure their involvement in this process. NDIS-participating laboratories shall not consider a request for a manual comparison of missing person-related records submitted by a non-law enforcement agency or organization.

When a laboratory receives a request for a manual comparison, all available information will be reviewed by the laboratory personnel. This includes not only the DNA data but other case-specific information (metadata), such as:

  • The missing person’s date of disappearance
  • The date the remains were found
  • The estimated age of the remains
  • The age of the missing person
  • Any other identifying features

Using this information, the NDIS participating laboratory will determine whether a routine search of NMPDD would be expected to produce an association. Based on this review, the laboratory may, in its discretion, deny the request for a manual comparison. If the genetic information from the human remains and/or relatives is limited, the laboratory may perform the comparison in accordance with its policies and protocols. When a manual comparison cannot exclude the possibility of a positive association, the laboratory will provide a report to the investigating agency that includes the appropriate kinship statistics.

If the DNA data for the human remains and reference samples are maintained by multiple NDIS participating laboratories, the laboratories will collaborate to exchange both DNA data and metadata. Once the comparison has been completed, the participating laboratories will ensure that all involved law enforcement agencies, medico-legal authorities, and laboratories are informed of the results.

Note: NDIS-participating laboratories do not have the legal authority to declare or confirm the identity of human remains. That determination will be made by the appropriate medico-legal authority (e.g., medical examiner or coroner).

Guidelines for Requesting a Missing Person Manual Comparison

  1. All requests for missing person manual comparisons must be submitted to the NDIS participating laboratory by the law enforcement agency or medico-legal authority responsible for the case.
  2. Non-law enforcement agencies or organizations seeking additional information or a manual comparison will submit the request to the law enforcement agency or medico-legal authority responsible for the case. That agency/authority will forward the request to the appropriate NDIS-participating laboratory. NDIS-participating laboratories will not consider requests received directly from non-law enforcement agencies or organizations.
  3. If the DNA data related to the case is maintained by multiple NDIS participating laboratories, the requesting agency will make reasonable efforts to determine the laboratories involved and provide that information with the request for a manual comparison.
  4. The NDIS-participating laboratory/laboratories maintaining the relevant DNA profiles will evaluate the data to determine, in its/their discretion, if a manual comparison is warranted. This evaluation will include:
    1. A comparison of metadata related to the individual reported missing and the human remains recovered
    2. A review of the available DNA data for completeness, number of available references, and their relationship to the missing person
  5. In the event of a positive association, all law enforcement agencies and medico-legal authorities involved in the case will be notified by an NDIS-participating laboratory. These participating laboratories will not provide laboratory reports or notifications to non-law enforcement agencies or organizations.


  • Direct questions regarding the Missing Persons program within the NDIS to the FBI Laboratory’s CODIS Unit at (703) 632-8315.
  • Direct questions regarding a specific case or comparison to the NDIS-participating laboratory that maintains the DNA data.