The Interstate Identification Index or III (pronounced "triple-eye") is a national index of criminal histories (or rap sheets) in the United States of America, maintained by the Federal Bureau of Investigation (FBI) at the National Crime Information Center. Included in this index are individuals who have been arrested or indicted for "a serious criminal offense anywhere in the country".
The program is designed to facilitate the interstate exchange of criminal history records among State justice agencies. In addition to the interstate exchange, this index holds millions of fingerprint identification cards for criminals who have committed a serious enough crime to go to jail for over 24 hours.
Search results from the III give a list of states that have a criminal history on a given person. An investigator or analyst may then query those states directly to get specific criminal history, either through the National Law Enforcement Telecommunications System (NLETS) or by other means.
This makes the criminal justice system of each participating state no longer a completely closed system; the increased exchange of information between different law enforcement agencies increases the chances of bringing multi-state offenders to justice.