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). Included in this index are individuals who have been arrested or indicted for "a serious criminal offense anywhere in the country."[1] Search results from the III give a list of states that have 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. Simply put, if all the criminal histories of each state were put in one (very large) book, the III would be the index.
This is significant because the criminal justice system of each participating state is now no longer a completely closed system; the increased exchange of information between different law enforcement agencies increases the chances of catching multi-state offenders.