Combined DNA Identification System (CODIS) is the DNA database system launched by the Federal Bureau of Investigation (FBI) to support the criminal justice system based on DNA identification. It is basically a software that runs the identification process.

The FBI initiated a pilot project of DNA databasing in the United States, along with 14 participating local and state laboratories. Then in 1994, the Congressional DNA Identification Act authorized the FBI to establish a national database that includes- DNA identification profiles of the persons convicted of crimes and analysis of DNA samples recovered from crime scenes and unidentified human remains.

By 1997, 13 STR loci were selected and in 1998 they were implemented as the core loci for the national database, the CODIS.

Levels of CODIS

CODIS has three hierarchical levels namely: Local DNA identification system (LDIS), State DNA identification system (SDIS), and National DNA identification system (NDIS).

  • Local DNA Identification System is maintained at crime laboratories operated by police departments, sheriff’s offices, and local agencies.
  • A State DNA Identification System is maintained in each state and operated by a designated state laboratory. The DNA profiles stored in LDIS are directed to SDIS. SDIS also stores the DNA profiles generated from the state laboratories. It serves as the communication path through which LDIS and NDIS are able to exchange messages through encryption. 
  • National DNA Identification System is the highest level of the CODIS infrastructure, which contains DNA profiles contributed by the participating state and local laboratories. NDIS stores DNA profiles generated by federal laboratories, such as the FBI and the US Army Criminal Investigation Laboratory. Search for DNA profiles is allowed at a national level. All DNA profiles submitted to NDIS are automatically searched weekly against the state DNA profiles.

A search through the CODIS database may be requested either from the FBI or the International Police Organisation (INTERPOL).

Who is The Main Character of CODIS?

CODIS works on the principle of identifying the short tandem repeats(STRs) present in the DNA fragments. STRs are the repeated regions of DNA fragments that do not code for any protein. The STRs vary in length among individuals and are easy to analyze.

FBI has identified 13 STR loci for identification in CODIS and they are- CSF1PO, D3S1358, D5S818, D7S820, D8S1179, D13S317, D16S539, D18S51, D21S11, FGA, TH01, TPOX, vWA.

Here the question arises that why only 13 STRs are used for DNA profiling. Karen Norrgard, Ph.D. in his research paper. Forensics, DNA Fingerprinting, and CODIS explained that at the crime scene, the quantity of DNA samples is very small, and sometimes the samples may contain DNA from multiple sources.

If less than 13 core STRs are considered for DNA profiling, then the probability of a random match will be increased due to an increase in overall genotype frequency, which will complicate the identification procedure.

As of January 2017, the requirements to upload the profile is 20 STR loci, i.e., 7 more STR loci are identified that are- D1S1656, D2S441, D2S1338, D10S1248, D12S391, D19S433, D22S1045.

The number of repeats present in STR is called alleles. If the fragment of DNA contains the same alleles then it is called homozygous whereas the presence of different alleles on the DNA fragment makes it heterozygous. This also helps in differentiating the individuals.

How CODIS is Operated?

The DNA is extracted from the biological sample, STR regions are identified and directed to PCR amplification.  The 13 core STRs vary in length from 100 to 300 bases, allowing even partially degraded DNA samples to be successfully analyzed.

The STR loci vary in their complexity, for example, D7S820 STR is simple whereas D21S11 has complex patterns that vary in size by single base-pair because of the need to differentiate single-base differences, PCR products are typically resolved using automated DNA sequencing technologies with software that recognizes allele patterns by comparison to a known “ladder.”

The matching is done by allele profiling at all the 13 STR loci of the evidence sample and the suspect’s sample. If the match is negative then the suspect is excluded but if the match is positive, then a statistical calculation would be made to determine the frequency with which this genotype is observed in the population.

This calculation gives the frequency of the alleles in the individual’s ethnic group. A simple Hardy-Weinberg calculation is performed to get the frequency of the observed genotype of each STR. Multiplying together the frequencies of the individual STR genotypes then gives the overall profile frequency.

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.

Advantages of CODIS

The advantages of applying CODIS include:

  • It is one of the most useful techniques used for forensic DNA analysis.
  • STR alleles can be rapidly determined using commercially available kits.
  • STR alleles are discrete and behave according to known principles of population genetics.
  • The data are digital and therefore ideally suited for computer databases.
  • Laboratories worldwide are contributing to the analysis of STR allele frequency in different human populations
  • STR profiles can be determined with very small amounts of DNA

DNA Databases of India & Other Nations

CODIS is not the first database system to be established in the world. It was the NDNAD (National DNA Database) from the United Kingdom, in 1995. By the end of 1998, the national DNA database systems were introduced in Austria, Germany, Netherlands, New Zealand, and Slovenia.

In India, no such database system has been established yet. However, it was decided to follow the UK’s example of setting up a DNA database and a bill named The DNA Technology Regulation Bill was proposed in the Lok Sabha in July 2019. It was then sent to the Parliamentary committee where it was criticized for its misuse and ethical issues. 


Various statistical reports around the world have shown the growing rate of crimes against human beings and their investigation is time-consuming. DNA analysis has been proven useful in the accurate identification process.

Therefore it is important to establish DNA databases like CODIS in every nation to help in providing justice through the use of DNA profiles. It is not only useful in determining conviction but in some cases, it has been proven helpful in verifying innocence.

Also Have a Look at:

Frequently Asked Questions

1. Who Invented CODIS?

CODIS was maintained and invented by the Federal Bureau of Investigation.

2. Has CODIS Ever Been Hacked?

CODIS is maintained and protected by FBIs encryption and firewalls and is very secure. Hence, the CODIS has never been breached.

3. Why Was CODIS Originally Created?

CODIS was invented to create a database of the state’s convicted criminal’s DNA profile and use it to solve crimes for which no suspect is under the radar of investigators.

Categories: Fingerprints


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