Combined DNA Index System (CODIS)

Date: Established in 1990

Identification: Database maintained by the Federal Bureau of Investigation that stores DNA profiles for comparison purposes, used by federal, state, and local crime laboratories.

Significance: CODIS allows forensic laboratories to compare DNA profiles related to crimes (forensic profiles) to those obtained from other crimes or from individuals previously convicted of felonies. Through such comparisons, links may be found between crime scenes and repeat offenders may be identified.

The Combined DNA Index System, better known as CODIS, was established as the result of a suggestion from the Technical Working Group on DNA Analysis Methods; the intent was to create a national database of DNA (deoxyribonucleic acid) profiles collected from convicted criminals. When CODIS was initiated in 1990 as a pilot project of the Federal Bureau of Investigation (FBI), it included fourteen state and local laboratories.

The DNA Identification Act of 1994 allowed the formation of a national DNA database and clarified which types of DNA evidence could be stored in it. DNA profiles from persons convicted of crimes, evidentiary items obtained from crime scenes, and unidentified human remains were to be included, as well as profiles voluntarily submitted by relatives of missing persons. In 1998, the national database became operational, and by 2003 it was accepted by all fifty states. Qualified city, county, regional, state, and federal crime laboratories, as well as labs in several in other countries, now contribute to this powerful crime-solving tool.

Structure of the Database

CODIS is operational at three tiers: the National DNA Index System (NDIS), the State DNA Index System (SDIS), and the Local DNA Index System (LDIS) levels. A DNA profile originates locally and then migrates to the state and national levels. This approach allows each state access to a database that is concurrent with its individual legislation, including what crimes will result in submission of a DNA profile (for example, sexual assault, any violent crime, all felonies).

CODIS consists of two main databases: the forensic index and the convicted offender index. The forensic index contains data on DNA profiles obtained from victims or crime scenes, whereas the convicted offender index includes the profiles of those convicted of offenses. Using the two indexing systems, it is possible to link crimes together for the purpose of identifying a repeat perpetrator or to link a crime to a person who is or was in prison. Other databases existing in CODIS include the arrestees index, the missing persons index, the unidentified human remains index, and the biological relatives of missing persons index. Whether an individual state participates in these at the national level depends on state policy or law. In order for a state to be eligible to participate in CODIS, the appropriate state authority must sign a memorandum indicating that the state’s laboratory (or laboratories) adheres to FBI quality assurance standards; the laboratory must also pass a series of inspections and subsequent reviews.

A DNA profile found in CODIS contains only the following: an identification code for the submitting agency, an identification number for the specimen, the DNA profile itself, and the name of the person who submitted the information. Only the submitting laboratory can place a name on a DNA profile. The limited data ensure that the DNA profiles are not exploited and that the identities of those whose profiles are submitted to the database are protected. It is also important to note that the profiles do not contain any information about medical conditions. CODIS is accessible only to those working within the field of law enforcement. Participating laboratories submit their information through a secure intranet called CJIS WAN, which is located in Clarksburg, West Virginia.

Putting a DNA Sample Through CODIS

DNA samples can be taken from convicted persons in several different ways. Blood or buccal swabs (swabs of the inside of the cheek) are generally collected, although in theory almost any tissue could be used. Forensic samples come from a huge variety of sources, the most common being semen from sexual assault cases, but blood, hair, saliva, bone, or virtually any other tissue or body fluid can be tested. New developments have allowed for touch samples—samples extracted from items that have come into direct contact with the persons of interest (such as held objects)—to be used also as potential sources of profiles.

DNA profile information is submitted to CODIS in the form of short tandem repeats (STRs). Thirteen core STR loci were chosen for use with CODIS; the profiles of convicted offenders must contain all thirteen of these loci to be uploaded to CODIS, whereas forensic profiles, which often originate from less-than-ideal sources, are required to have at least ten loci.

At the local level, analysts have some leeway when searching the database. For instance, a laboratory may require that a complete match be made at a locus for that locus to be considered, whereas another laboratory, recognizing that degraded DNA from a crime scene can result in the loss of part of a profile, might find a partial profile probative. Likewise, the minimum number of loci needed to be considered informative can vary from case to case.

After a potential match has been found by CODIS, the laboratories responsible for the corresponding profiles must contact each other to authenticate the results. The samples are often then retested to ensure the validity of the match. Upon confirmation that the two profiles are consistent with each other, the laboratories exchange any additional information they need.

Bibliography

Balding, D. J., and P. J. Donnelly. “Evaluating DNA Profile Evidence When the Suspect Is Identified Through a Database Search.” Journal of Forensic Sciences 41 (1996): 603–7.

Butler, John M. Forensic DNA Typing: Biology, Technology, and Genetics of STR Markers. 2d ed. Burlington, Mass.: Elsevier Academic Press, 2005.

Houck, Max M., and Jay A. Siegel. Fundamentals of Forensic Science. 3rd ed, Elsevier/Academic Press, 2015.

Mercer, Stephen, and Jessica Gabel. “Shadow Dwellers: The Underregulated World of State and Local DNA Databases.” New York University Annual Survey of American Law, vol. 69, no. 3, 2014, pp. 639–97. Legal Source, search.ebscohost.com/login.aspx?direct=true&db=lgs&AN=100913984&site=eds-live. Accessed 30 Dec. 2016.

National Research Council. The Evaluation of Forensic DNA Evidence. Washington, D.C.: National Academy Press, 1996.

Walton, Richard H. Cold Case Homicides: Practical Investigative Techniques. Boca Raton, Fla.: CRC Press, 2006.