In the courthouse lobby, the short, white-haired man seemed to be more clothes than body, bundled in a coat and scarf. It was a December day in 2013.

“Let me hold your arm,” he said. “If you don’t mind.”

With that, Myron Beldock took my forearm. Short, slow steps brought him to the curb on Monroe Place in Brooklyn Heights, and then into a cab with his wife and legal partner, Karen L. Dippold. Some months earlier, a closing door had knocked him down, and doctors looking at his shoulder found cancer. Due in the appellate division to argue the cause of an innocent man he had been representing for years, Mr. Beldock had stopped taking pain killers a few days before, fretting that the medicine might cost him a step in court.

He got out of his sickbed and made his case that December, and was pleased with the reactions of the judges but unwilling to predict their decision, which was months off.

“Not a bad day,” he said getting in the cab, age 84, now the tail of a comet.

Mr. Beldock, who died on Monday, had an important hand in cases that helped define the landscape of 20th-century law, and in others that merely righted the grievous wrongs done to unknown people.