Professor Slocum earned his B.S. from Newark College of Engineering (now New Jersey Institute of Technology). He worked as an electrical engineer for almost a decade, during which time he became active in the NAACP. As an NAACP official, he saw the law as in dire need of reform and decided to go to law school. He received his J.D. from Rutgers-Newark in 1970 and, upon graduation, was appointed to the faculty. He later earned his master of laws degree at Yale Law School. While a student at Rutgers, Professor Slocum became a spokesperson for the rights of people of color and other minorities within the law school community. Together with Professor Frank Askin and others, he formed a committee that led to the creation of the Minority Student Program – the most extensive and renowned program to train minority lawyers of any school in the U.S.
In 1974, Professor Slocum took a leave of absence to serve as executive director of the Council on Legal Education Opportunity (CLEO). Sponsored by the American Bar Association and funded by Congress, CLEO was the first national organization dedicated to recruiting minority students into law schools. He was elected president of CLEO in 1984. Professor Slocum became Public Advocate of the State of New Jersey in 1986 and later that year was appointed Public Defender. For five years he championed the causes of the voiceless underclass and the indigent defendant. In 1990 he returned to the law school where he taught until retiring from the faculty in 2001.
Professor Slocum has served on the board of the Essex County Legal Services Program and the Puerto Rican Legal Defense and Education Fund. He was for many years an active member of the National Conference on Black Lawyers and has served as general counsel of the National Organization of Black Law Enforcement Executives. He also served on several New Jersey Supreme Court committees, including the Committee on Racial Bias and the Court and the Committee on Jury Selection and Its Impact on Racial Minorities.