1. A method for conducting a criminal background investigation of a person by using a pre-existing computer database that contains information about many persons, comprising the steps of: determining identifying information about a person whose background is to be investigated; determining the probability that information concerning the person of interest is not available in the computer database, including creating at least one probability measure, said at least one probability measure including determining the number of counties within a predetermined distance of a given county; determining which information in the computer database relates to the person of interest and which does not; creating an offense array that ranks offenses by level of severity and general crime category; applying information about the person of interest to the offense array; and creating an offense score for the person of interest.