• County Courthouses: Counties generally have the most complete criminal history information. In most instances, county courthouses contain information about felonies, misdemeanors, infractions, and traffic violations in addition to arrests, cases without dispositions and expunged cases. Depending on the county, a search may be performed online or onsite. InfoMart recommends performing a search of every county of current or previous residence for every applicant.
• State Repositories: State databases of criminal information are compiled from county data. Because states rely on counties to report criminal information, such reporting can be inconsistent or infrequent and all levels of offenses may not be reported. To avoid obtaining inaccurate information from state repositories, InfoMart has developed a list of Recommended Statewide Searches for our clients.
• Federal Records Center: Only federal felony and misdemeanor records are available from this source. This constitutes a fairly narrow body of information because the vast majority of criminal activity concerns violations of state law. For federal cases, the only identifier available is name, which can make identification of a particular individual difficult.
• Multi-State Criminal History Search: InfoMart offers a Multi-State Criminal Search, which can contain a wealth of criminal information otherwise undisclosed by an applicant. The Multi-State Criminal Search contains record information from states representing over 90% of the population and has over 250 million records. The Multi-State Criminal Search is an effective "pre-screen" tool which, combined with a jurisdiction criminal history search, identifies criminal history records that otherwise would never be discovered.

(Source: http://www.seyfarth.com)