Marshall, who had been sick for a short time, died Monday night at his home in suburban Mount Kisco, said his agent, Clifford Stevens.
He starred as lawyer Lawrence Preston in The Defenders, a popular CBS courtroom drama series that ran from 1961 to 1965. His portrayal of the father in a father-and-son law firm won him Emmys in 1962 and 1963.
Marshall had reprised his role in The Defenders for two Showtime episodes in the 1997-1998 season.
His movie credits included The Caine Mutiny, The Silver Chalice, The Left Hand of God, Twelve Angry Men, Cash McCall, Town Without Pity, Compulsion, The Bridge at Remagen and Superman 2.
On Broadway he appeared in The Petrified Forest, The Iceman Cometh, The Skin of our Teeth, Jacobowsky and the Colonel, The Gambler, The Crucible and Waiting for Godot.
His distinctive voice was heard on commercials, and he was often used as a narrator or a host. He did the narration for In Memoriam: J.F.K. in 1966 and for several years was host of the annual PBS July 4 production, A Capitol Fourth.
Marshall's portrayals of politicians were so convincing that people sometimes mistook the distinguished looking actor for an actual lawmaker.
"I was on the phone in the Senate wing of the Capitol," he once recalled. "A woman asked me how to get to the third floor Senate gallery. She said, 'You must know, you're a senator.'"
He did have some experience in politics. He formed an environmentalist political party for a local election here in 1988. "It was a civics lesson for me what it takes to get elected. Well, I didn't win," he recalled.
Everett G. Marshall was born June 18, 1910, in Owatonna, Minn., the son of Norwegian parents.
While attending the University of Minnesota, he weighed entering the Episcopal ministry but said he "gave up on the clergy" when he discovered his leanings toward agnosticism.
His thespian course was determined in 1932 when he got started in radio in St. Paul and then moved on to Chicago where he performed with the Theater Guild on the Air.
The following year he joined a touring Shakespearean repertory company and eventually made it to Broadway. His first appearance was in a Federal Theater Project production of Prologue to Glory in 1938.
His film debut came in 1945 when he played a morgue attendant in The House on 92nd Street.
By the time he got the part in The Defenders, he estimated he had appeared in more than 400 TV shows, including Kraft Television Theatre, the Hallmark Hall of Fame, Playhouse 90 and Philco Playhouse.
The Defendrs, however, changed things for him.
"Although I'd been on television playing various parts, of course almost constantly for years, nobody seemed to recognize me on the street or in restaurants," he said in 1962. "Now people are likely to turn around and look at me."
He played the part of Dr. David Craig in the NBC series The New Doctors from 1969 to 1973. His character headed a combination hospital and research center dedicated to finding new medical techniques.
In the 1970s, Marshall also returned to his radio roots as host of the CBS Radio Mystery Theater.
He continued to act in his 80s, appearing in a summer stock presentation of Park Your Car in Harvard Yard in Westport, Conn., in 1992. He played an aging tycoon whose wife, the president's mistress, is murdered in the 1997 Clint Eastwood film, Absolute Power.
Marshall married Helen Wolf in 1939; they were divorced in 1953. They had a daughter, Jill, and a son, Degen.
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