As the oldest judge on the appeals court based in Boston, Bruce Selya has turned to a younger colleague asking for a promise: if he sees a change in the 88-year-old’s sharpness, tell him.

“I completely respect that if he noticed any sign of diminution in the quality of my opinions, or my behavior, or argument, that he would come to me and just be straight with me about it,” said Selya, who joined the U.S. Court of Appeals for the First Circuit in 1986 and took senior status in 2008.