NICS scans federal databases like the National Crime Information Center and Interstate Identification Index for information. If a purchaser has been convicted of a felony, or misdemeanours with sentences exceeding two years, or has been declared "mentally defective" by a court, then he or she won't pass the background check.
However, denials are rare, occurring less than 1% of the time. "More than 100 million such checks have been made in the last decade, leading to more than 700,000 denials," the FBI says on its website.
But gun buyers don't have to go through a background check when they make a purchase at a gun show.
Most Americans live somewhere near a gun show. The website
www.gunshows-usa.com lists 29 gun shows scheduled for this coming Father's Day weekend, from Las Vegas and Philadelphia to Hickory, N.C. and Salmon, Idaho.
You won't find them in cities like New York, Chicago and Washington, D.C., where gun laws are far more restrictive.