DNA Testing

Combined DNA Index System (CODIS)


The Combined DNA Index System, or CODIS, blends forensic science and computer technology into a tool for linking violent crimes. It enables federal, state, and local forensic laboratories to exchange and compare DNA records electronically, thereby linking serial violent crimes to each other and to known offenders and assisting in the identification of missing and unidentified individuals. States contribute their authorized and eligible DNA records to the National DNA Index System (NDIS) - the highest level of the CODIS hierarchy - where they are stored and searched on a daily basis.

CODIS generates investigative leads in cases where biological evidence is recovered from a crime scene. For example, 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 Program began as a pilot software project in 1990, serving 14 state and local laboratories. The DNA Identification Act of 1994 (see Federal DNA Identification Act under National DNA Index System below) formalized the FBI’s authority to establish a National DNA Index System (NDIS) for law enforcement purposes. Today, over 200 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. 

CODIS Resources:

National DNA Index System (NDIS)  

The National DNA Index System, or NDIS, is the national level of the CODIS System. NDIS contains DNA records contributed by participating federal, state, and local forensic laboratories. The DNA Identification Act of 1994 (34 U.S.C. §12592) authorized the establishment of this National DNA Index. The DNA Act specifies the categories of data that may be maintained in NDIS, as well as requirements for participating laboratories relating to quality assurance, privacy, and expungement.  

NDIS was implemented in October 1998 in accordance with the Federal DNA Identification Act. Effective August 2017, the Rapid DNA Act was enacted and authorized the Director of the Federal Bureau of Investigation to issue standards and procedures for the use of Rapid DNA instruments and resulting DNA analyses. 


All 50 states, the District of Columbia, the federal government, the U.S. Army Criminal Investigation Laboratory, and Puerto Rico participate in NDIS. 

Pursuant to the Federal DNA Identification Act, participation requirements for NDIS include, but are not limited to, the following: 

  • Status as a federal, state, or local criminal justice agency (“or the Secretary of Defense in accordance with section 1565 of title 10, United States Code”); 
  • Compliance with the FBI Director’s Quality Assurance Standards;  
  • Accreditation by a nonprofit professional association of persons actively engaged in forensic science that is nationally recognized within the forensic science community;  
  • Undergoing an external audit every two years to demonstrate compliance with the FBI Director’s Quality Assurance Standards; and  
  • Restricting access to, and limiting disclosure of, the DNA records in accordance with the provisions of the Federal DNA Act. 

NDIS Procedures Board  

The FBI empaneled an NDIS Procedures Board to develop procedures on the operation of the National DNA Index.  Chaired by the Chief of the FBI’s CODIS Unit, the current NDIS Procedures Board consists of 2 representatives of the FBI Laboratory’s DNA-related units, the NDIS Custodian, 6 representatives from state and local forensic DNA laboratories, the Chair of the Scientific Working Group on DNA Analysis Methods (SWGDAM) and a representative elected by the State CODIS Administrators.  The NDIS Procedures Board meets periodically to address issues raised by CODIS users and Administrators; to provide guidance for the users and the FBI on operational issues; and to ensure that such operational procedures comply with federal law and regulations. 

CODIS Core Loci  

DNA records submitted to NDIS by participating laboratories must contain the CODIS Core Loci. An additional seven loci were added to the CODIS Core effective January 1, 2017—D1S1656, D2S441, D2S1338, D10S1248, D12S391, D19S433 and D22S1045. See Selection and implementation of expanded CODIS core loci in the United States, D.R. Hares, Forensic Sci. Int. Genetics 17:33-34 (2015).  Following is a listing of the 20 CODIS Core Loci. 

  • CSF1PO 
  • D3S1358 
  • D5S818 
  • D7S820 
  • D8S1179 
  • D13S317 
  • D16S539 
  • D18S51 
  • D21S11 
  • FGA 
  • TH01 
  • TPOX 
  • vWA 
  • D1S1656 (effective January 1, 2017) 
  • D2S441 (effective January 1, 2017) 
  • D2S1338 (effective January 1, 2017) 
  • D10S1248 (effective January 1, 2017) 
  • D12S391 (effective January 1, 2017) 
  • D19S433 (effective January 1, 2017) 
  • D22S1045 (effective January 1, 2017) 

The STR Standardization Project recognized the importance of balancing the privacy issues attendant to storing genetic information with ensuring the effectiveness of this criminal justice DNA database 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). 

Because they were selected as law enforcement markers to be used for identification purposes only, the CODIS loci were specifically chosen because: (1) none are located within a gene or protein coding region; (2) they are located in regions commonly referred to as “junk DNA”; and (3) they have been studied and found to not be causative or indicative of any medical condition or disease status that could compromise an individual’s medical privacy.  Additionally, it is important to note that any reported correlation between a CODIS marker and a coding gene for a specific medical condition or disease does not necessarily mean that the CODIS marker is now linked or predictive of that medical condition without supporting studies that establish a functional role of the CODIS STR loci or variant in disease causation. 

To date, the CODIS STR loci continue to be studied for their predictive value and no CODIS locus or forensic STR variant has been demonstrated to directly cause or predict disease (external link).  Additionally, professional groups such as the Scientific Working Group on DNA Analysis Methods (SWGDAM) continue to investigate and publish on this topic as appropriate such as its Open SWGDAM Letter Regarding the Claims Raised in State v. Abernathy that the CODIS Core Loci are Associated with Medical Conditions/Disease States available at swgdam.org/publications

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, titled 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.

The most recent Quality Assurance Standards were revised and took effect July 1, 2020.  The accompanying Audit Documents and the Guidance Document applicable to both the Databasing and Forensic Standards can be found below. Please note that the QAS Guidance Document was recently updated and is effective as of January 1, 2023. 

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

Rapid DNA Analysis is the fully automated (hands-free) process of developing a CODIS acceptable STR profile from a database, known or casework reference sample. The “swab in-profile out” process consists of automated extraction, amplification, separation, detection, and allele calling without human intervention. 

The FBI Laboratory has been involved in the integration of Rapid DNA Analysis into the CODIS Program since 2010.  Federal legislation authorizing the use of Rapid DNA analysis to generate DNA records for storage and searching at the National DNA Index System was signed into law in August 2017. 

Learn more about Rapid DNA analysis, including the FBI’s efforts to integrate it into the arrestee booking station process as well as efforts to develop standards and procedures for the use Rapid DNA analysis for crime scene samples. 

Additional Resources 


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.