Samuel Walker is Professor Emeritus of Criminal Justice at the University of Nebraska at Omaha. After retiring in 2005 he has continued his research, writing and consulting on police accountability, citizen oversight of the police, early intervention systems for police officers, and civil liberties.

Professor Walker is the author of 14 books, which have appeared in 33 different editions. His most recent book is Presidents and Civil Liberties from Wilson to Obama (2012). His other books include The Police in America: An Introduction [with Charles M. Katz] (8th ed., 2013), Police Accountability: The Role of Citizen Oversight (2001), Taming the System: The Control of Discretion in Criminal Justice, 1950–1990 (1993), Sense and Nonsense About Crime (7th ed., 2011), The Color of Justice: Race, Ethnicity, and Crime in America (with C. Spohn & M. De Lone) (5th ed., 2003), and In Defense of American Liberties: A History of the ACLU (2nd ed., 2000). He is the author of Early Intervention Systems for Law Enforcement Agencies: A Planning and Management Guide (2003), published by the COPS Office of the U.S. Department of Justice.

Professor Walker has served as a consultant to the Civil Rights Division of the U.S. Department of Justice and to police departments, local governments and community groups in over 35 cities and counties across the country on different police issues.