John M. O’Donnell, Justice Department lawyer

John M. O’Donnell, a retired antitrust lawyer who served in the Justice Department for four decades, died March 28 at his home in Bethesda. He was 91.

He had pneumonia, said his daughter Peggy O’Donnell.

Mr. O’Donnell joined the Justice Department in the early 1950s and oversaw cases involving proposed mergers and possible monopolies. In 1975, he served on the staff of President Gerald R. Ford’s clemency board. He retired in 1980.

John Michael O’Donnell was born in Troy, N.Y. He served in the Army during World War II. Before moving to Washington, he worked in lumberyards in New York.

He was a 1950 graduate of Catholic University and a 1953 graduate of American University’s law school.

He was a volunteer with Montgomery County police.

Survivors include his wife of 64 years, Mildred Broscious O’Donnell of Bethesda; five children, M.A. O’Donnell of Chevy Chase, Peggy O’Donnell and Anne O’Donnell, both of Philadelphia, Michael O’Donnell of Akron, Ohio, Frank O’Donnell of Groveland, Mass., and John M. O’Donnell Jr. of Chicago; four brothers; and four grandchildren.

— T. Rees Shapiro