More than 500 people in federal prison for selling crack in Pennsylvania could be released early under new sentencing guidelines designed to reduce disparities that punished dealers more harshly than those who sold the powdered form. Drug policy experts said the changes are long overdue in a system designed in response to panic over the crack epidemic perceived across the nation in the 1980s."They were enacted in a climate of fear and lots of media attention about how crack was affecting our communities," said Steven Belenko, a professor of criminal justice at Temple.