Robert B. von Mehren, the last surviving lawyer in the infamous Alger Hiss trials, died Thursday at his home in Manhattan. He was 93.

The cause of death was congestive heart failure, according to his wife, Susan Heller Anderson, a writer and former reporter for The New York Times. A longtime seasonal resident of Chilmark, Mr. von Mehren bought his home from James Cagney in 1957.

As a young lawyer for the firm that is now Debevoise & Plimpton, Mr. von Mehren served on the defense counsel team representing Alger Hiss, a highly regarded former government official, during his two trials for perjury in 1949 and 1950. Whittaker Chambers, an editor at Time magazine and former Communist Party member, had testified before the Committee for the Investigation of Un-American Activities of the House of Representatives (also known as HUAC) and accused Mr. Hiss, then president of the Carnegie Endowment for International Peace, of being a Communist Party member and a spy for the Soviet Union while working for the U.S. government. Newspapers labeled The United States of America v. Alger Hiss “the trial of the century.”

“No criminal case had a more far-reaching effect on modern American politics than the Alger Hiss-Whittaker Chambers spy case, which held Americans spellbound in the middle of the twentieth century,” wrote Douglas Linder in the University of Missouri School of Law Journal. “The case catapulted an obscure California congressman named Richard Nixon to national fame, set the stage for Senator Joseph McCarthy’s notorious Communist hunting, and marked the beginning of a conservative intellectual and political movement that would one day put Ronald Reagan in the White House.”

Richard M. Nixon subsequently became nationally famous for his pursuit of Communists, especially Mr. Hiss, and 20 years later he was elected president. He revealed later, in the Watergate tapes, that he had mounted a systematic campaign of leaking information that would turn opinion against Hiss. “We won the Hiss case in the papers...I had to leak stuff all over the place. Because the Justice Department would not prosecute it. Hoover didn’t even cooperate. We had to develop a program, a program for leaking out information,” Nixon said on the tapes.

During the pretrial discovery process, Chambers produced evidence indicating that he and Hiss had been involved in espionage, which both men had denied previously under oath to HUAC. A federal grand jury indicted Hiss on two counts of perjury, as the statute of limitations had expired for the charge of espionage. After a first mistrial due to a hung jury, Hiss was tried a second time and, in January 1950, he was found guilty and sentenced to two concurrent five-year prison terms, of which he eventually served three and a half years. Mr. von Mehren, who worked almost exclusively on the Hiss case for nearly three years, attended every day of both trials and maintained contact with Mr. Hiss until the latter’s death in 1996. He believed that the proper decision, had it been possible, would have been the Scottish law verdict of “Not Proved.”

Among the many positions Mr. von Mehren held outside the law firm, those of which he was proudest were as legal counsel to the Preparatory Commission of the International Atomic Energy Agency, which composed the guidelines for the United Nations agency that exist today; consultant to the Rand Corporation on disarmament; consultant to the Hudson Institute on international law, and senior lecturer of law at the Wharton School, University of Pennsylvania.

Before his retirement as a partner in 1995, he was chairman of Debevoise’s litigation department and served as lead counsel in many landmark arbitrations, including Texaco Overseas Petroleum Company and California Asiatic Oil Company vs. the Government of Libya, protecting overseas assets invested in nationalized foreign governments’ property, a case ongoing today.

An active proselytizer of arbitration in dispute resolutions, Mr. von Mehren taught and lectured frequently all over the world. He pioneered international arbitration among American lawyers, serving in more than four dozen arbitrations after he “retired” from Debevoise. A prolific contributor to legal publications, he was a co-editor of American Arbitration: Principles and Practice (2009).

His pro bono positions included chairman, vice chairman and/or president of the International Law Association, the Practicing Law Institute, the American branch of the International Law Association, several committees of the City Bar Association of New York and the Harvard Law School Association of New York. He was an honorary member of the Commercial Bar of London and the Singapore Bar. He was also on the board of the American Arbitration Association, a fellow of the American Bar Foundation, the vice-president emeritus of the Axe-Hougton Foundation, and a member of the Council on Foreign Relations, the Century Association and the University Club.

Born in Albert Lea, Minn., he won a national scholarship to Yale University and graduated summa cum laude, then magna cum laude from the Harvard Law School, where he served as president of the law review in 1946. Upon graduation he became associated with Debevoise, where he spent most of his career until he became an international arbitrator. He clerked for Second Circuit Court of Appeals Judge Learned Hand, whose bawdy limericks he delighted in reciting from memory, and Supreme Court Justice Stanley F. Reed. He retired from arbitrating in 2013.

An avid sailor, Mr. von Mehren raced his beloved sailboat, the Mariner Phalarope, on Martha’s Vineyard, where he owned a home on North Road in Chilmark that he bought from the actor James Cagney in 1957.

In addition to his wife, Mr. von Mehren is survived by his loving children: a son, Carl; three daughters, Katharine, Jane and Margaret; and Philip D. Anderson, his stepson. He was predeceased by his first wife, Mary Katharine, his younger son, John, and his identical twin, Arthur T. von Mehren.

In lieu of flowers contributions may be made in his name to the Sheriff’s Meadow Foundation, 57 David avenue, Vineyard Haven MA 02568. A private interment will be held in October at Abel’s Hill Cemetery, following which the family will receive friends at an address to be announced.