- Connecticut, New York and U.S. Tax Court, 1970
- U.S. District Court, District of Connecticut, 1971
- U.S. Circuit Court of Appeals, 2nd Circuit and U.S. Claims Court, 1972
- Florida, 1975
- NY University School of Law, LL.M. (Taxation)
Associations & memberships
- Connecticut (Member: Section on Taxation; Executive Committee Young Lawyers Section, 1976-1980; Young Lawyers Tax Section, Chairman, 1976-1980), New York State and American (Member: Section on Taxation Committee on Civil and Criminal Tax Penalties, Subcommittee on Criminal Penalties, 1975-1983) Bar Associations
- The Florida Bar
Member, Connecticut Estate and Tax Planning Council, Board of Directors, 1981-1984. Chairman, Zoning Board of Appeals, Woodbridge, Connecticut, 1983-1995, 1997-2004. Connecticut Pension Consultants, Member, 1981-1990 and Director, 1985-1988. Town Moderator, Town of Woodbridge, 1994-1998.
Marshal D. Gibson Professional Corporation serves clients in New Haven and throughout Connecticut, New York and Florida.