The Combined DNA Index System is a database of DNA profiles from offender samples and case samples, which are used to assist investigations of cold criminal cases and prosecutions. The DNA profiles in the database are based on body fluid or hair left at the crime scene or collected from suspects and convicted offenders. By using the DNA database, criminal investigations with no suspects can be solved and assailants unknown to the victims can be identified. Matches made among profiles in the database can link crime scenes together, possibly identifying serial offenders. Based on a match, police in multiple jurisdictions can coordinate their respective investigations, and share the leads they developed independently. Suspects can also be identified when matches are made between case samples and offender samples. After CODIS identifies a potential match, qualified DNA analysts in the laboratories contact each other to validate or refute the match.
In 1995, the Texas Legislature passed a bill that established the DNA database and allowed DPS to begin compiling a database of DNA profiles of all sexual offenders in Texas and unknown forensic case samples. State law now requires all felons to provide DNA samples. Samples are also required from juveniles who have been committed to the Texas Youth Commission (TYC) for a felony offense. Probationers may also be required to provide a sample as a condition of probation regardless of offense.
The functional role of DPS in the DNA database is basically three-fold:
The success of the CODIS program is demonstrated by its ability to match DNA evidence samples to convicted offenders or other forensic samples in the database. On average, approximately 70 investigative leads are generated monthly by the CODIS program.