Historically, the attitudes of professional workers and researchers can be divided into four periods. The first period, from 1860 to 1919, is referred to as the hereditary era when the prevailing attitude was that all "feeble-minded" individuals were hereditarily predisposed to criminal behavior. The second period, from 1916 to 1925, is called the low intelligence era, during which opinions were widely held that low intelligence was the major cause of crime and antisocial behavior. The third and fourth periods are the environmental era (1925-1945) and the multiple factors era (1946-present). The current multiple factors era represents an eclectic approach to explain the relationship between criminal behavior and mental retardation that includes biological, psychological, social, and legal determinants. Due to the varied perspectives on mental retardation and criminality, there is no real agreement on the etiology of criminal behavior among the mentally retarded. Retarded individuals are at a decided disadvantage in the judicial system, and such biasing disadvantages mitigate against being able to use court data to effectively determine the relationship between crime and mental retardation. 35 references