Paul R. Connolly, 56, a partner in the noted Washington law firm of Williams & Connolly, died yesterday at Georgetown University Hospital following a heart attack.

Like Edward Bennett Williams, who is regarded as one of the leading criminal lawyers in the nation, Mr. Connolly was a trial lawyer. Like Williams, he defended many persons charged with criminal offenses. But his specialty was civil litigation. In the 30 years that he practiced here, he tried cases ranging from personal injuries and contracts to antitrust matters and the Alaska pipeline.

Mr. Connolly and Williams became partners in 1967. One was expert in criminal law, the other in civil law, and their firm was capable of any kind of trial work.

In 1971, they were joined by Joseph A. Califano Jr., who had been President Johnson's chief adviser on domestic affairs and who now is secretary of Health, Education and Welfare. Califano, the 17th lawyer to join the firm, concentrated on corporate affairs, and the scope of legal services offered by what was then known as Williams, Connolly & Califano expanded. Williams & Connolly, which includes The Washington Post among its clients, now has more than 50 lawyers.

Both Williams and Califano credited Mr. Connolly with a major role in this growth.

"He made a tremendous contribution," Williams said. "I regarded him as one of the finest lawyers I ever knew."

"In human terms, he was the most decent person I ever met," Califano said. "He loved to litigate, he loved the law. In the law firm, he was the glue in terms of keeping everybody together."

Associates described Mr. Connolly as a perfectionist who tried each case as if it was to be his last.

Among his more publicized cases was the defense of Otto Kerner, former governor of Illinois and then a U.S. Court of Appeals judge. Kerner and Theodore J. Isaacs, who had been Illinois state revenue director, were convicted of bribery, conspiracy and related charges in connection with a scheme in which they were said to have bought race track stock at favorable terms and then granted favors to the tracks owners.

He won a case before the U.S. Supreme Court in which he represented Maryland colleges with church connections.The American Civil Liberties Union had challenged the Maryland state practice of providing financial aid to these institutions. The ACLU said that such aid violated the doctrine of separation of church and state.

In a case involving ownership of a device that separated the meat from chicken necks, Mr. Connolly suggested that members of the jury be permitted to ask questions about how it worked. The court agreed to this novel suggestion. Mr. Connolly's client won.

Mr. Connolly was not in awe of judges. A judge in the U.S. District Court in Washington twice overruled him in a case involving a contract, and then said:

"The court is watching you, Mr. Connolly."

"Mr. Connolly is watching the court," Mr. Connolly replied.

Paul Raymond Connolly was born in Baltimore on June 28, 1922. He remained a devout member of The Catholic Church throughout his life. Despite the hard times of the Great Depression, he was able to go to Loyola College in Baltimore and graduated in 1943.

He entered the Navy and is believed to have been the first American officer to visit Hiroshima after it was devastated by the atomic bomb on Aug. 6, 1945, in the closing days of World War II. Mr. Connolly, a lieutenant aboard the destroyer John Pierce, arrived in the city Aug. 15, the day after the Japanese surrender. It was an experience he often recalled in later years.

"It was the only time in my life I have really been ashamed to be an American," he told People magazine in 1975.

"People cowered by the side of the road. Many of them were badly disfigured with large sores running on their arms and faces. They had these vacant looks in their eyes, just a haunting terror.'God,' you said to yourself, 'these are human beings and we've done this' . . .. No one who has seen the results of an atomic bomb could consider using it again," he said.

Mr. Connolly entered Georgetown University Law School after his discharge from the Navy. There he met Edward Bennett Williams, who taught a course that Mr. Connolly took. Williams recruited him for the prestigious Washington law firm of Hogan & Hartson, and Mr. Connolly went to work there in 1948. Williams himself was just setting up his own practice.

Mr. Connolly remained with Hogan & Hartson until he resigned to join Williams.

Mr. Connolly was a former chairman of the litigation section of the American Bar Association. Last year he chaired a seminar on white-collar crime that he described as "the fastest growing legal specialty in the United States." He elaborated on his views in a speech to students in which he said:

"Once we understand - as older Josuits and their students will - that the prime matter of white-collar crime is money and dishonesty its substantial form, the reason for its proliferation is obvious. Our society has become so materialistic that money is nearly its only value and the competition for it has become so intense and the need for it so great that the means for its acquisition are tested, not by any morality, but by utility and acceptability. Never mind that the means are not honest. The test is, do they work?"

Mr. Connolly concluded by recalling an axiom he attributed to his mother: "Don't do anything you would not want to read about on the front page of the (Baltimore) Sunpapers."

An associate recalled that Mr. Connolly also lived by another maxim: "Take one case each year on behalf of one person or one cause that needs you and can't afford you."

Mr. Connolly was a member of the American, District of Columbia and Maryland bar associations. He was a fellow of the American College of Trial Lawyers and a former adjunct professor of law at Georgetown University.

He also was a member of the Metropolitan, Chevy Chase, George Town, Burning Tree and Mid-Ocean clubs.

Survivors include his wife, the former Mary Catherine Garvey, whom he married in 1948, of the home in Washington, and six children, Mary Tressa Hamby, of Reston, Paul Brian, of Chevy Chase, Margaret C., of Washington, Sheila B., of Chevy Chase, Michael Ignatius, a student at Pomona College in Claremont, Calif., and Peter Christopher, of the home.

Williams said he would ask Chief Judge William B. Bryant to adjourn the U.S. District Court here at the close of today's business in memory of his partner.