Stuart A. Schlesinger spent half a century building a reputation and a practice as a personal injury lawyer in New York, representing clients in lawsuits and negotiating settlements on their behalf. But when he appeared recently before a federal judge in Manhattan, he found himself in an unfamiliar position for a lawyer: He was the defendant.

Mr. Schlesinger, 76, had been arrested on a fraud charge in one of the more brazen schemes in the annals of New York law: He settled lawsuits on behalf of clients, sometimes for $1 million or more, and then simply kept much of the money for himself.

When his clients complained that they had not received the proceeds of their settlements, Mr. Schlesinger responded with a litany of excuses. “We are short-staffed,” he said in an email to one client, Kenneth Lawler, a British man who was owed more than $900,000 from the settlement of a medical malpractice lawsuit stemming from the death of his son in a New Jersey hospital. “Our phones and computer systems were down,” Mr. Schlesinger wrote in another email to Mr. Lawler. “Sorry for the delay,” he said in a third email, adding strangely, “Waiting for our golf game.”

Mr. Lawler, 63, said that now, four years after the settlement was reached, he had not yet received a penny. “It’s a betrayal,” he said.