Richard Widmark, a self-effacing actor who played cackling maniacs, dedicated public servants and maverick leading men with equal distinction during a five-decade career in film and television, died March 24 at his home in Roxbury, Conn. He was 93.

His wife, Susan Blanchard, said yesterday that Mr. Widmark had been ill for a long time, and she did not elaborate. "He was a very private man," she said.

A veteran of more than 70 films, Mr. Widmark showed enormous range: strong military men ("Halls of Montezuma," "The Bedford Incident"), obsessed detectives ("Madigan"), Western heroes ("The Alamo") and insolent underworld figures, notably his explosive debut as a cold-blooded killer in 1947's "Kiss of Death."

Mr. Widmark was "a quiet genius" and "the kind of star whose mastery sneaks up on you," Film Comment magazine noted. Director Samuel Fuller once said Mr. Widmark was an ideal choice to play modern, complex heroes. "He could be a heavy, he could be the lead," Fuller said. "He could go either way."

Mr. Widmark had an unconventional leading-man face, almost gaunt with a lock of blond hair falling on his high forehead. It took several years before he was cast as a protagonist, and even then, his good guys were often misanthropes or men fixated on a mission.

His renown initially came from playing streetwise heavies, starting with "Kiss of Death." As Tommy Udo, he elevated his high-pitched giggle to a sinister art form. In the film's most memorable scene, he gleefully tied an old lady into a wheelchair and shoved her down a staircase.

"Kiss of Death" brought Mr. Widmark his only Academy Award nomination, for a supporting role. By many accounts, he stole the show from the nominal star, Victor Mature, as a crook who turns state's evidence and is preyed upon by Udo.

Reviewer Pauline Kael wrote that when Mr. Widmark grins onscreen, "his white teeth are more alarming than fangs."

Although he continued to play bad guys in several more pictures, Mr. Widmark said he did not want audiences to believe his acting was limited to Udo's quirks. "For two years after that picture," he told the New Yorker magazine, "you couldn't get me to smile."

He was the asthmatic gangland boss in "The Street With No Name" (1948); the racist patient who taunts a black medical resident (played by Sidney Poitier) in Joseph L. Mankiewicz's "No Way Out" (1950); a doomed American hustler in London in Jules Dassin's "Night and the City" (1950); and a pickpocket who helps uncover a communist spy ring in Fuller's "Pickup on South Street" (1953).

Poitier later wrote in a memoir that Widmark "was the most pleasant and refreshing surprise in my initial exposure to the Hollywood scene. The reality of Widmark was a thousand miles from the characters he played. That shy, gentle, very private person helped me to learn the ropes of filmmaking and was among the first in Hollywood . . . to open his home to me socially."

Mr. Widmark tried to persuade studio bosses to put him in more sympathetic parts. He felt so out of place in "No Way Out" that he kept apologizing to co-star Poitier between takes for the racist dialogue.

His bosses eventually recognized his versatility: In Elia Kazan's "Panic in the Streets" (1950), he was the Public Health Service doctor who tracks down a criminal carrying the plague around New Orleans. In "Don't Bother to Knock" (1952), he was an airline pilot easily seduced by a mentally disturbed babysitter (played by Marilyn Monroe in one of her key early parts).

He once said Monroe was "God-awful to work with. Impossible, really." He said she shut herself in her dressing room, appeared nervous when she came out and seemed constantly distracted, behavior that contrasted with Mr. Widmark's low-key demeanor and devotion to craft.

Mr. Widmark said his fame in "Kiss of Death" at 33, an older age than when most leading men achieve success, spurred a lifelong wariness of celebrity culture.

"I never thought I was a star," he once told a reporter. "I always figured I was a working actor waiting for the next job." Fame, he also said, "was all baloney and could blow away in a minute."

His idol was Spencer Tracy, with whom he appeared as the resentful son in "Broken Lance" (1954) and as the American prosecutor to Tracy's judge in "Judgment at Nuremberg" (1961). He said Tracy was the "greatest listener in this business," working deceptively hard at making each line appear natural.

One of Mr. Widmark's last hits was Don Siegel's "Madigan" (1968), a remake of Akira Kurosawa's "Stray Dog" (1949). He played Daniel Madigan, a police detective who single-mindedly hunts down a man who stole his gun. The film set a standard for later movies about distressed cops, such as Siegel's "Dirty Harry."

"I suppose I wanted to act in order to have a place in the sun," Mr. Widmark told the New Yorker. "I'd always lived in small towns, and acting meant having some kind of identity."

He was born Dec. 26, 1914, in Sunrise, Minn., to a salesman and his wife. The family settled in Princeton, Ill., where Mr. Widmark played football, wrote for the school paper and was active in his school drama club. A moviegoer since his grandmother first took him at age 3, he said he always wanted to be a film actor.

He was a speech and political science graduate of Lake Forest College in Illinois, and he taught in the school's drama department. A classmate helped him get a job on a New York radio show, "Aunt Jenny's Real Life Stories," and soon he was getting bigger radio and theater parts.

He performed regularly in the 1940s after a perforated eardrum exempted him from military service during World War II.

He said he specialized in portraying "young, neurotic guys" on radio, which led to his being cast in "Kiss of Death." Twentieth Century Fox studio chief Darryl F. Zanuck hired him as Udo over the objections of director Henry Hathaway, who wanted to use a nightclub habitu¿ named Harry the Hipster.

Mr. Widmark's memorable staircase encounter with the old lady was the first scene filmed. Despite its effectiveness, Hathaway made life hard on the set for the inexperienced film actor, either not talking to him at all or embarrassing him in front of others. One day, after the director insulted him, Mr. Widmark quit and walked off the set.

He said Hathaway's assistant chased him and asked the actor to have lunch with the director. It was a wordless meal, but a respect was born. "After that, Henry left me alone," he said.

They worked together on several more films, including "Down to the Sea in Ships" (1949) and "Garden of Evil" (1954).

Mr. Widmark said he was glad when his seven-year studio contract ended so he could have more control over his choice of roles. In 1958, he was Robert Taylor's threatening former partner in "The Law and Jake Wade" and Doris Day's husband in the adoption comedy "The Tunnel of Love."

He formed a production company in the late 1950s and went on to appear as Jim Bowie in John Wayne's only directorial effort, "The Alamo" (1960). His other Westerns of the period included "How the West Was Won" and two of director John Ford's final films, "Two Rode Together" and "Cheyenne Autumn."

Despite his largely positive notices, he acknowledged he made some duds. He once joked that he forced his daughter to watch "Run for the Sun," his 1956jungle adventure film, when she misbehaved.

Generally reserved except about his liberal political beliefs, he said he modeled his portrayal of a recklessly hardened Cold War destroyer captain in "The Bedford Incident (1965) on Sen. Barry Goldwater (R-Ariz.), the conservative presidential candidate in 1964.

Starting in the 1970s, his age made leading parts scarce. He took roles, often with scripts he considered ludicrous ("The Swarm," for example), for the fun of working alongside top-flight actors.

He accepted the part of the corpse in "Murder on the Orient Express" (1974) just so he could say John Gielgud played his valet.

His first wife, Jean Hazlewood Widmark, whom he married in 1942, died in 1997.

In addition to his wife, whom he married in 1999, survivors include a daughter from his first marriage, Anne Heath Widmark of Santa Fe, N.M., who was divorced from Baseball Hall of Famer Sandy Koufax.