According to the Encyclopedia Britannica, the due process revolution affected policing by changing the way that police officers went about their day-to-day duties. In addition, because the new guidelines required a higher degree of professionalism, police departments raised their recruiting standards, revamped training programs and initiated new procedures in the detainment and interrogation of suspects.
The due process revolution came about in the wake of several United States Supreme Court decisions in the 1960s. The first of these, in 1961, stipulated that evidence obtained by unlawful search and seizure could not be used in court. In 1964, the Supreme Court determined that if a suspect was not provided counsel upon request, his statements during trial were inadmissible as evidence. In 1966, the Supreme Court ruled that, before interrogation, the police must inform a suspect of his rights to remain silent and to have counsel present. This required police to quote what became known as "the Miranda rights" to a suspect upon arrest.
The principle of due process is mentioned twice in the U.S. Constitution, once in the fifth amendment and again in the fourteenth. In both places, it uses the same language, that no one shall be "deprived of life, liberty or property without due process of law." The first usage is in reference to the federal government, and the second is in reference to state governments.