The National Instant Criminal Background Check System (NICS) was implemented on November 30, 1998 as a result of the Brady Handgun Violence Prevention Act of 1993. NICS is a national system used by Federal Firearms Licensees to instantly determine whether a prospective buyer is eligible to buy firearms by checking available records.
The NICS searches three nationally held databases with every check.
The Interstate Identification Index (III), which houses criminal history records; the National Crime Information Center (NCIC), which houses records such as warrants and protection orders; and the NICS Index.
The NICS Index was created specifically for use by the NICS and contains descriptive information on persons determined to be disqualified from possessing a firearm based upon state or federal law.
Local, state, federal, and tribal entities voluntarily contribute information to the NICS Index. This information contains prohibiting information that may not be found in the III or the NCIC. It should be noted that felony data is usually contained in the III, and, therefore, there may be few or no entries in this category in the NICS Index. In contrast, the NICS Index is the logical location to share adjudicated mental health data if the law allows.
The contributing agency is responsible for the accuracy and validity of the information; therefore, additions, deletions, and modifications are expected and occur on an on-going basis.