WASHINGTON — Justice Anthony M. Kennedy is a fierce critic of solitary confinement. “It drives men mad,” he said in 2015 at Harvard Law School.

He attacked the practice in a 2015 concurring opinion. “Years on end of near total isolation exact a terrible price,” he wrote, noting that “common side effects of solitary confinement include anxiety, panic, withdrawal, hallucinations, self-mutilation, and suicidal thoughts and behaviors.”

Justice Kennedy concluded that opinion with an unusual request, inviting lawyers to file appeals challenging the constitutionality of prolonged isolation. The requested appeals arrived, but the Supreme Court has so far turned them down. The court, which typically moves in measured increments, may not want to take on a question as broad as whether extended solitary confinement is cruel and unusual punishment barred by the Eighth Amendment.

But the court will soon consider whether to hear appeals raising a much narrower question: Do prisoners held in solitary confinement have a right to regular outdoor exercise?