J. Harold Flannery graduated from Wilkes University and the University of Pennsylvania Law School. He began his legal career in the Civil Rights Division of the Department of Justice. Serving in that capacity for a decade, Justice Flannery litigated cases fighting against segregation and other civil rights violations. He served under such Attorneys General as Robert Kennedy and Nicholas Katzenbach.
After his time at the Department of Justice, he worked for the Harvard University Center for Law and Education for four years before returning to Washington to serve as the national director of the Lawyers Committee for Civil Rights Under the Law. Justice Flannery was involved in two landmark desegregation cases during that time: the Boston busing case Morgan v. Hennigan, 379 F. Supp. 410 (D. Mass. 1974), and the Detroit busing case Milliken v. Bradley, 418 U.S. 717 (1974). In 1975 Justice Flannery became a partner at the law firm of Foley Hoag LLP and maintained that position until Governor Michael Dukakis appointed him to the Superior Court in 1984. Governor William Weld appointed Justice Flannery to the Appeals Court in 1995. He was also an adjunct professor at Northeastern Law School, teaching trial practice. He passed away on December 8, 1998.
The Appeals Court's Memorial to Justice Flannery may be found at 49 Mass. App. Ct. 1123 (2000).