Combined DNA Index System

While CODIS is generally used for linking crimes to other crimes and potentially to suspects there are non-criminal portions of the database such as the missing person indexes. The National Missing Person DNA Database, also known as CODIS(mp), is maintained by the FBI at the NDIS level of CODIS allowing all states to share information with one another. Created in 2000 using the existing CODIS infrastructure, this section of the database is designed to help identify human remains by collecting and storing DNA information on the missing or the relatives of missing individuals.[7][8] Unidentified remains are processed for DNA by the University of North Texas Center for Human Identification which is funded by the National Institute of Justice.[9] Nuclear, Y-STR (for males only), and mitochondrial analysis can be performed on both unknown remains and on known relatives in order to maximize the chance of identifying remains.[7]

As of September 2020, NDIS contained more than 14 million offender profiles, more than 4 million arrestee profiles and more than one million forensic profiles.[10][11] The effectiveness of CODIS is measured by the number of investigations aided through database hits. As of September 2020, CODIS had aided in over 520 thousand investigations and produced more than 530 thousand hits.[10][11] Each state has their own SDIS database and each state can set their own inclusionary standards that can be less strict than the national level. For this reason, a number of profiles that are present in state level databases are not in the national database and are not routinely searched across state lines.[12]

The original 13 core loci and their locations on the genome plus the sex determining locus Amelogenin (AMEL).

Prior to January 1, 2017, the national level of CODIS required that known offender profiles have a set of 13 loci called the "CODIS core". Since then, the requirement has expanded to include seven additional loci. Partial profiles are also allowed in CODIS in separate indexes and are common in crime scene samples that are degraded or are mixtures of multiple individuals. Upload of these profiles to the national level of CODIS requires at least eight of the core loci to be present as well as a profile rarity of 1 in 10 million (calculated using population statistics).[4]

Loci that fall within a gene are named after the gene. For example, TPOX, is named after the human thyroid peroxidase gene.[16] Loci that do not fall within genes are given a standard naming scheme for uniformity. These loci are named D + the chromosome the locus is on + S + the order in which the location on that chromosome was described. For example, D3S1358 is on the third chromosome and is the 1358th location described.[17] The CODIS core are listed below; loci with asterisks are the new core and were added to the list in January 2017.[18]

The loci used in CODIS were chosen because they are in regions of noncoding DNA, sections that do not code for proteins. These sections should not be able to tell investigators any additional information about the person such as their hair or eye color, or their race.[19] However, new advancements in the understanding of genetic markers and ancestry have indicated that the CODIS loci may contain phenotypic information.[20][21]

Current laws governing DNA collection as of 2018.

     Collection upon conviction only
     Collection from some felony arrests
     Collection from all felony arrests

The original purpose of the CODIS database was to build upon the sex offender registry through the DNA collection of convicted sex offenders.[22] Over time, that has expanded. Currently, all 50 states collect DNA from those convicted of felonies. A number of states also collect samples from juveniles as well as those who are arrested, but not yet convicted, of a crime.[11][23] Note that even in states which limit collection of DNA retained in the state database only to those convicted of a crime, local databases, such as the forensic laboratory operated by New York City's Office of Chief Medical Examiner, may collect DNA samples of arrestees who have not been convicted. The collection of arrestee samples raised constitutional issues, specifically the Fourth Amendment prohibiting unreasonable search and seizure. It was argued that the collection of DNA from those that were not convicted of a crime, without an explicit order to collect, was considered a warrantless search and therefore unlawful.[24] In 2013, the United States Supreme Court ruled in Maryland v. King that the collection of DNA from those arrested for a crime, but not yet convicted, is part of the police booking procedure and is reasonable when that collection is used for identification purposes.[25]

The inheritance pattern of some DNA means that close relatives share a higher percentage of alleles between each other than with other, random, members of society.[26] This allows for the searching of close matches within CODIS when an exact match is not found. By focusing on close matches, investigators can potentially find a close relative whose profile is in CODIS narrowing their search to one specific family. Familial searching has led to several convictions after the exhaustion of all other leads including the Grim Sleeper serial killer.[27] This practice also raised Fourth Amendment challenges as the individual who ends up being charged with a crime was only implicated because someone else's DNA was in the CODIS database.[28] As of April 2018, twelve states have approved the use of familial searching in CODIS.[29]