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What Is CODIS?
Updated on September 13, 2023
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What Is CODIS?
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Combined DNA Index System (CODIS) is a computer software developed by the Federal Bureau of Investigation (FBI). It was made to support DNA databases across the country.1

Inside CODIS is the National DNA Index System (NDIS). The national DNA database contains DNA profiles shared by federal, state, and other cooperating labs.

The CODIS software makes it easy for law enforcement to compare DNA profiles left at crime scenes to DNA profiles of convicted offenders.

A DNA match can help detectives locate potential suspects during criminal investigations. It can also link recent crimes to older cases on file, which can be helpful in unsolved crimes.

How Does CODIS Work?

CODIS generates hits or matches by pulling its information from two entries:2

  • Forensic index — contains DNA profiles obtained from crime scene samples
  • Convicted index — has DNA profiles of people convicted for violent crimes

CODIS matches may contain investigative leads for crimes with biological evidence.

The software doesn’t store personally identifiable information, such as names. It only has a set of ID characters. This makes it easy to search profiles on the national database.3

State laws define which convicted offender must enter their profiles into their database. Some states require all felons to submit their DNA profiles.

The CODIS database allows forensic crime labs from different states and authorities to collaborate on the same crime investigation.

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What Does A CODIS Hit Mean?

A CODIS hit means a genetic match between two or more DNA profiles in the databases. Law enforcement can use it as a lead in solving cases. 

There are two types of CODIS hits:

Forensic Hit

A forensic hit is a match between forensic evidence from two or more cases. The agencies that submit the forensic samples can use them as a lead in crimes they’re handling. 

It can help in cases involving missing persons and unidentified remains, especially of close relatives. It can also uncover leads in cases of a suspected serial killer.

Offender Hit

An offender hit means the crime scene evidence matches a convicted offender’s genetic profile. 

It can identify them as potential suspects in a crime.

What Happens After A CODIS Hit?

Once CODIS identifies a match between two DNA profiles, the forensic labs that submitted them can start coordinating. They can exchange information about the matching DNA profiles.

A law enforcement agency can use CODIS matches to legally obtain DNA samples from the suspect. They can present the file to get a court order for DNA collection.

The casework lab can run a DNA analysis on the same DNA they collected from the crime scene and the potential suspect. This can confirm an exact match.

The detective can include the DNA results as evidence in court. Of course, they still need to investigate further and prove the offender’s involvement in the crime.

Example of How CODIS Works

In cases of sexual assault, the medical examiner can collect biological samples from the victim and create a DNA profile of the unknown perpetrator.

They can compare the unknown DNA to the state’s Convicted Offender and Arrestee Index. Investigators can also run the DNA profile against the Forensic Index.

If a match shows up, they can confirm the offender’s identity with the lab. Matching DNA profiles may also link two or more crimes if the DNA belongs to a repeat offender.

The law enforcement agencies handling the connected cases may exchange information. They can also work together and develop additional leads to help with their criminal investigation.

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Updated on September 13, 2023
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1 sources cited
Updated on September 13, 2023
  1. What Is CODIS?” National Institute of Justice.
  2. Understanding DNA Evidence: A Guide for Victim Service Providers.” U.S. Department of Justice.
  3. Frequently Asked Questions on CODIS and NDIS.” Federal Bureau of Investigation.

Cristine Santander
Cristine Santander
Content Contributor
Cristine Santander is a content writer for KnowYourDNA. She has a B.S. in Psychology and enjoys writing about health and wellness.
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