R. Kenneth Mundy, a dynamic Washington lawyer who could weave magic in a courtroom and was best known for defending Mayor Marion Barry against drug charges in 1990, died yesterday of a heart attack.

Mundy, 63, of Kensington, was taken to Holy Cross Hospital yesterday morning suffering from "respiratory distress" and was pronounced dead a few minutes later, according to a hospital spokesman.

One of the city's premier criminal litigators, Mundy in recent years had become the man to call for prominent people in trouble. His client list included former Congress members Mary Rose Oakar and Dan Rostenkowski, who had retained him after a nationwide search for co-counsel. He had defended former Maryland state senator Tommie Broadwater Jr. and won acquittal on federal mail fraud and perjury charges for Robert L. Green, a former president of the University of the District of Columbia.

As Barry's lead attorney in the mayor's perjury and drug trial, Mundy took strategic risks and wooed jurors with fiery rhetoric to beat back the most serious charges. The trial ended with Barry convicted of one misdemeanor cocaine possession charge and acquitted of a second, and the jury deadlocked on 12 other charges.

Mundy was "one of the most brilliant lawyers that this country will ever produce, which was evidenced in his representation of me in 1990," Barry said yesterday.

Mundy's defense of Barry brought him to national prominence, but many lawyers say he had been a legend around Washington area courthouses long before, particularly since his defense 16 years ago of Terrence Johnson, a black teenager charged with killing two white police officers in Prince George's County.

Mundy began practicing in the District in 1957 as one of the first black lawyers hired by the Federal Communications Commission. He moved into private practice in 1965 with his own small firm, practiced alone at times, and at the time of his death had a firm downtown, Mundy, Holt & Mance. As word of his abilities spread, he came to be called the "Edward Bennett Williams of the black community."

Mundy, who came equipped with wit, mischief and an abundance of confidence, ran into the reporter who wrote that phrase in a column shortly after it appeared. Mundy complimented the reporter on the piece and then told him, only half-jokingly, that he "should have called Edward Bennett Williams the Ken Mundy of the white community.' "

Mundy could joke about such things, but he grew up in the legal profession when black lawyers were rarely, if ever, hired by establishment law firms and when even wizardry like Mundy's seldom propelled them to national prominence. Mundy took on all kinds of cases, representing people in everything from crime to divorce to small business matters. He often represented lawyers accused of ethical misconduct, and did so for free because they were facing personal ruin. And his reputation grew.

Judges who watched Mundy work and lawyers who fought him across the courtroom said Mundy could find the strengths and weaknesses in any case and exploit them to their ultimate. U.S. Attorney Eric H. Holder Jr. recalled a judge once marveling at Mundy's skills in a criminal trial: "Man, you've got to see what Mundy is doing," Holder recalled the judge saying. "He's . . . working with nothing and he may be winning the case."

Mundy simply disarmed jurors, several admirers said. "He was able to convey to everyone, the judge, the jury, that he was a very nice person," said D.C. Superior Court Judge Henry H. Kennedy Jr. "I know this sounds pollyannish. . . . But sometimes jurors attribute to the client the qualities of the lawyer. His clients profited greatly from the respect that his demeanor and manner commanded."

None of it was just for show. The term "gentleman" was the one most often used to describe him, usually with the word "consummate" as the preface. Former federal prosecutor Nancy Luque recalled trying a murder case opposite Mundy. It was the first time they'd faced each other in the courtroom, and as the jury filed in, Mundy unobtrusively slipped her a note on a little edge of paper torn off his legal pad. It said: "Good luck. Good trial."

When the trial ended and Mundy had suffered one of his rare defeats, she said, he "turned to me and was incredibly gracious." In between, "he was aggressive and powerful. . . . He already had a reputation as a force."

Mundy was born in Akron, Ohio, in 1932, and as a teenager he already seemed to be honing his skills for the courtroom. He won oratorical contests, said former D.C. Council Chairman Sterling Tucker, who grew up with Mundy. "It did not surprise anybody that he became a lawyer," Tucker said. "He loved the soapbox."

He graduated from Kent State University in 1953 and from Case Western Reserve Law School in 1957. He once joked that he chose law because there were few professional choices for blacks in those days. "The ministry seemed overcrowded," he said. "And as you can see, I like to talk."

Mundy often was at his best in the most sensitive and toughest cases, finessing juries as he did in the Barry case and in the racially charged murder trial in 1979 of Terrence Johnson, then 15 years old, who was charged with shooting and killing two white Prince George's County police officers while being detained on a minor charge. Mundy argued that Johnson had been abused while being held and perhaps even feared for his life when he reached for an officer's gun. In a dramatic verdict, the jury acquitted Johnson by reason of temporary insanity in one killing and convicted him of manslaughter in the second. It was the first case to bring Mundy widespread prominence in the Washington area.

The Barry case did the rest. On many days during the two-month trial, Mundy dazzled or surprised. During some critical parts of the direct testimony of Hazel Diane "Rasheeda" Moore, the government's key witness against Barry, Mundy either dozed or feigned dozing off, showing the jury just how much weight to give her assertions, recalled one reporter covering the case. Then he dismantled her on cross-examination. In closing arguments, Mundy dropped a bombshell, admitting publicly for the first time that Barry had been an occasional cocaine user but asserting that this was not the issue in the trial; that specific charges were the issues they must decide. It was a daring gamble, but Mundy and his client won.

Mundy was as much a personality outside the courtroom as in. His signature became his hats: a jaunty straw boater one day, a modest little Panama another, or something with a bold, wide brim. Almost never did he wear the same one twice.

But that was Mundy. Seldom without a quip, and always in motion. His news conferences rolled up and down the streets outside the federal courthouse, as he headed for the subway and fed reporters' deadline needs.

"He literally was moving at 100 miles an hour throughout the day," said Chicago lawyer Dan K. Webb, who chose Mundy as his co-counsel in the Rostenkowski case and worked with him in recent months. "The only time I ever saw him sit still was . . . in court."

Mundy drove his beloved moped on weekends and even last Sunday got in two hours of tennis with a longtime friend, Chief D.C. Superior Court Judge Eugene N. Hamilton. He often put in 13-hour office days, said his partner, Robert Mance. There were too many clients and too little time.

Mundy is survived by his wife, Mignon; his son, Keith; three grandchildren; and two brothers, Ralph Mundy, of Akron, and Alonzo Mundy, of Wheaton.

Hamilton said that Mundy had been trying to slow down of late, even raising his fees a bit to try to keep clients away. But it didn't work. "He was such a good trial lawyer," Hamilton said, "that for people really in trouble {who} needed a good defense, he was irresistible." CAPTION: R. Kenneth Mundy, right, arrives at court with Marion Barry. Mundy defended Barry against drug charges.