Interstate Agreement on Detainers Act. A law, originally enacted in 1956, in which the federal government, certain states, and the District of Columbia agree that a state may obtain custody of a prisoner for trial even though the prisoner is already incarcerated in another state. • Under the Act, if a prisoner makes a written request for disposition of the charges in the second state, the second state must try the prisoner within 180 days of the request. 18 USCA App. arts. I–IX. See UNIFORM MANDATORY DISPOSITION OF DETAINERS ACT.