Judge Frederic Block, who once wrote that he wished he could have overseen O.J. Simpson’s murder trial, has always reveled in the spotlight.

Now, at 91, Judge Block may get his own celebrity trial. He is presiding over the case of Rafael Caro Quintero, a Mexican drug lord charged with orchestrating the 1985 murder of an undercover D.E.A. agent — a killing that was dramatized in the Netflix series “Narcos.” Mr. Caro Quintero may face the death penalty.

It could be years before Mr. Caro Quintero goes on trial in Judge Block’s courtroom. And Judge Block could face a lengthy challenge of his fitness, endurance and ability to filter his courtroom vocabulary.

America’s judges, like its elected officials, are getting older. In 2020, the average age of federal judges was 69, older than in any point in history, according to The Ohio State Law Journal. In 2023, Pauline Newman, a 96-year-old federal judge, was suspended amid concerns over her mental fitness.

There are no indications that Judge Block, one of the nation’s oldest district court judges, is unfit for the task. He maintains an active life, attending operas, musicals and live jazz performances in his free time, and has full command of his courtroom.

“Most people think I still function pretty well as a federal judge,” Judge Block said as he leaned back in a leather couch in his chambers in Brooklyn’s Federal District Court, wearing a purple shirt and Nike sneakers. “I speak better than Biden.”