The Combined DNA Index System (CODIS) is a national database used in the United States to store and compare DNA profiles from crime scenes, convicted offenders, and missing persons. It helps law enforcement agencies identify suspects and solve cases by matching DNA evidence collected during investigations. CODIS operates at three levels: local, state, and national. Each level contains DNA profiles that can be searched against one another, facilitating collaboration among different jurisdictions. This system enhances the ability to link crimes and identify repeat offenders, ultimately aiding in the pursuit of justice.