WICHITA, Kan.  Judge Wesley E. Brown’s mere presence in his courtroom is seen as something of a daily miracle. His diminished frame is nearly lost behind the bench. A tube under his nose feeds him oxygen during hearings. And he warns lawyers preparing for lengthy court battles that he may not live to see the cases to completion, adding the old saying, “At this age, I’m not even buying green bananas.”

At 103, Judge Brown, of the United States District Court here, is old enough to have been unusually old when he enlisted during World War II. He is old enough to have witnessed a former law clerk’s appointment to serve beside him as a district judge  and, almost two decades later, the former clerk’s move to senior status. Judge Brown is so old, in fact, that in less than a year, should he survive, he will become the oldest practicing federal judge in the history of the United States.

Upon learning of the remarkable longevity of the man who was likely to sentence him to prison, Randy Hicks, like many defendants, became nervous. He worried whether Judge Brown was of sound enough mind to understand the legal issues of a complex wire fraud case and healthy enough to make it through what turned out to be two years of hearings. “And then,” he said, “I realized that people were probably thinking the same thing 20 years ago.”

“He might be up there another 20 years,” added Mr. Hicks, 40, who recently completed a 30-month sentence and calls himself an admirer of Judge Brown. “And I hope he is.”