Robert M. Boyd, 53, a retired D. C. police inspector who headed the homicide squad for many years and who was an instructor in behavioral science at the F.B.I Academy in Quantico, Va., died of cancer Sept. 21 at Mary Washington Hospital in Fredericksburg, Va.

Mr. Boyd, who was a graduate of the F.B.I. Academy, joined the D.C. police department in 1953 as an officer in the 3rd precinct. He subsequently served as a sergeant, lieutenant and homicide detective before being promoted to captain and commander of the department's homicide division, a position he held for a number of years.

He later was promoted to police inspector and was commander of the 7th district when he retired in 1976 to join the faculty at the F.B.I. Academy. d

Mr. Boyd, who was an instructor in the academy's behavorial science unit, was the first full-time instructor appointed to the academy from outside F.B.I. ranks. He lectured on homicide and robbery, areas in which he specialized during his police career. A former Montgomery County resident, he had lived in Fredericksburg since joining the academy.

He was born in Knoxville, Tenn., and moved to Washington with his family at an early age. He attended Eastern High School.

Mr. Boyd was a member of the F.B.I. National Associates, the Association of Retired Policemen of D.C., Harvard Associates in Police Science, the International Association of Chiefs of Police and the Appalachian Trial Club.

Survivors include his wife, Mary Ellen, of Fredericksburg, a son, Michael, of Gaithersburg, and a daughter, Susan, of New York City.

The family suggests that expressions of sympathy be in the form of contributions to the American Cancer Society.