Mental Retardation and Crime The vast majority of people with mental retardation never break the law. Nevertheless, mentally retarded people may be disproportionately represented in America’s persons. Although people with mental retardation constitute somewhere between 2.5 and 3 percent of U.S. population, experts estimate they may constitute between 2 and 10 percent of the prison population. The disproportionate number of persons with mental retardation in the incarcerated populatio......