If true, such practices would be a violation of civil rights. The U.S. Supreme Court ruled in 1964’s Massiah v. United States that police officers who use undercover informants to interrogate someone represented by counsel violate the accused’s Sixth Amendment right to an attorney. And failing to turn over exculpatory information on this practice is a violation of the defendant’s 14th Amendment due process rights under 1963’s Brady v. Maryland.