NICS Improvement Act of 2003 - Amends the Brady Handgun Violence Prevention Act to require: (1) the head of each Federal agency that has records relating to persons for whom receipt of a firearm would violate Federal or State law to provide that information to the Attorney General for inclusion in the National Instant Criminal Background Check System (NICS); (2) the agency, upon being made aware that the basis under which a record was made available no longer applies, to correct the record and notify the Attorney General; and (3) the Department of Homeland Security to make available to the Attorney General records relevant to a determination that a person is disqualified from possessing or receiving a firearm and information about a change in such person's status for removal from NICS, where appropriate.
Directs the Attorney General to make grants to: (1) States and Indian tribal governments to establish or upgrade information and identification technologies for firearms eligibility determinations; and (2) States for use by the State court system to improve the automation and transmittal to Federal and State record repositories of criminal history dispositions, records relevant to determining whether a person has been convicted of a misdemeanor crime of domestic violence, court orders, and mental health adjudications or commitments.
Requires: (1) the Director of the Bureau of Justice Statistics to study and evaluate NICS operations and to report annually to Congress and to specified States regarding best practices; and (2) the Comptroller General to conduct an audit of the expenditure of all funds appropriated for criminal records improvement to determine how the funds were expended.