Combined DNA Index System

The Combined DNA Index System (CODIS) is the FBI-funded computer system that solves crimes by searching DNA profiles developed by federal, state, and local crime laboratories.

Origins of CODIS
CODIS was an outgrowth of the Technical Working Group on DNA Analysis Methods (TWGDAM, now SWGDAM) which developed guidelines for standards of practice in U.S. and Canadian crime laboratories as they began DNA testing in the late 1980s.

TWGDAM was sponsored by the FBI Laboratory which hosted several scientific meetings a year at Quantico, VA, to accelerate development of laboratory guidelines and peer-reviewed papers to support forensic DNA testing which was, to some, an unproven forensic tool. TWGDAM completed a white paper in October 1989 which provided conceptual and operational concepts for a Combined DNA Index System to share DNA profiles among crime laboratories similarly to automated fingerprint matching which had become commonplace in law enforcement during the 1980s.

In late 1990, the FBI Laboratory began a pilot project with six state and local crime laboratories to develop software to support each lab's DNA testing and allow sharing of DNA profiles with other crime laboratories.

The DNA Identification Act of 1994 formally authorized the FBI to operate CODIS and set national standards for forensic DNA testing. TWGDAM guidelines served as interim standards until recommendations were provided by a DNA Advisory Board required under the Act.

CODIS Indexes and Database Structure


The word "Index" in the CODIS name is not arbitrary. CODIS was designed to be a system of pointers to help public US crime laboratories compare and exchange DNA profiles. CODIS is not a criminal history database like the National Crime Information Center (NCIC). A record in the CODIS database, known as a CODIS profile, consists of a specimen identifier, an identifier for the laboratory responsible for the profile, and the results of the DNA analysis (known as the DNA profile). Other than the DNA profile, CODIS does not contain any personal identity information -- the system does not store names, dates of birth, social security numbers, etc.

In its original form, CODIS consisted of two indexes: the Convicted Offender Index and the Forensic Index. The Convicted Offender Index contains profiles of individuals convicted of crimes; state law governs which specific crimes are eligible for CODIS. (All 50 states have passed DNA legislation authorization the collection of DNA profiles from convicted offenders for submission to CODIS.) The Forensic Index contains profiles developed from biological material found at crime-scenes.

In the past several years, CODIS has added several other indexes, including: an Arrestee Index, a Missing or Unidentified Persons Index, and a Missing Persons Reference Index.

CODIS has a matching algorithm that searches the various indexes against one another according to strict rules that protect personal privacy. For solving rapes and homicides, CODIS searches the Forensic Index against itself and against the Offender Index. A Forensic to Forensic match provides an investigative lead that connects two or more previously unlinked cases. A Forensic to Offender match actually provides a suspect for an otherwise unsolved case. It is important to note that the CODIS matching algorithm only produces a list of candidate matches. Each candidate match is confirmed or refuted by a Qualified DNA Analyst. (To become Qualified, a DNA Analyst must meet specific education and experience requirements and undergo semi-annual proficiency tests administered by a 3rd party.)

CODIS databases exist at the local, state, and national levels. This tiered architecture allows crime laboratories to control their own data -- each laboratory decides which profiles it will share with the rest of the country. As of 2006, approximately 180 laboratories in all 50 states participate in CODIS. The national level, the National DNA Index System, or NDIS, is operated by the FBI at an undisclosed location.

Relative size
As of May 2007, 177,870 forensic profiles and 4,582,516 offender profiles have been accumulated, making it the largest DNA databank in the world, surpassing the United Kingdom's National DNA Database, which consisted of an estimated 3,976,090 profiles as of June 2007. As of the same date, CODIS has produced over 49,400 matches to requests, assisting in more than 50,343 investigations.

The growing public approval of DNA databases has seen the creation and expansion of many states' own DNA databanks. California currently maintains the third largest DNA databank in the world (naturally, as CODIS contains all states' databank information). Political measures such as California Proposition 69 (2004), which increased the scope of the databank, have already met with a significant increase in numbers of investigations aided.

In order to decrease the number of irrelevant matches at NDIS, the Convicted Offender Index requires all 13 CODIS STRs to be present for a profile upload. Forensic profiles only require 10 of the STRs to be present for an upload.

Privacy concerns
The CODIS database originally was only used to collect DNA of convicted sex offenders. Over time, this has expanded. Currently all fifty states have mandatory DNA collection from sex offenders and nearly 40 states from all convicted felons. Other states have gone further in collecting DNA samples from juveniles and all suspects arrested. In California, as a result of Proposition 69 in 2004, within five years all suspects arrested for a felony, as well as some individuals convicted of misdemeanors, will mandatorially have their DNA collected. In addition to this, all members of the US Armed Services who are convicted at a Special Court Martial and above are ordered to provide DNA samples, even if their crime has no civilian equivalent (for example adultery).

Currently, the ACLU is concerned with the increased use of collecting DNA from arrested suspects rather than DNA testing for convicted felons. Along with the ACLU, civil libertarians oppose the use of a DNA database for privacy concerns as well as possible institutionalized discrimination policies in collection.