Alper was born in Revere, Massachusetts and attended Harvard College and the Harvard Institute of Criminal Law.[2] After completing his studies worked for Massachusetts Juvenile Court (1933-1935), Charlestown State Prison and the Federal Bureau of Prisons.[3] Alper also worked as a research director of the Massachusetts Child Council, the New York State Legislature's Committee on the Courts (1941) and the American Parole Association (1942).[2]
In 1943 Alper joined the United States Army and served in North Africa and Italy.[4]
Alper was the first chief of the United Nations Criminal Justice and Crime Prevention Unit after its inception.[5] He was also a founding member of the United Nations Staff Association and its first president, until his dismissal in 1951 due to his objection to racial segregation in the UN blood drive.[6] His termination of the contract was one of the first brought before the Administrative Tribunal of the United Nations.[7]
Alper taught at The New School for Social Research and, from 1966 to 1993, was a professor at Boston College.[3] He was regarded as "a pioneer in advocating alternatives to traditional methods of punishment for juvenile offenders" and served as a member of the National Council on Crime and Delinquency and the Massachusetts Governor's Committee on Law Enforcement, Correctional Planning, Violence and Crime.[2]