Chief Justice William Rehnquist will celebrate his 81st birthday on Oct. 1, a noteworthy achievement that he can crown two days later by convening the next term of the U.S. Supreme Court.

By ruling out an imminent retirement last week, Rehnquist momentarily calmed feverish inside-the-Beltway speculation. His declaration raised the curtain, though, on the delicate question of how age and infirmity can shape justice, and on how much power judges enjoy to decide their own futures.

“I think they find it almost impossible to give up the job, for some very basic, human reasons,” Bruce Allen Murphy, a Supreme Court biographer and professor at Lafayette College in Pennsylvania, said in an interview. “There’s this very human impulse that you’re dealing with the end of your life; plus, giving up that kind of authority and attention has got to be hard.”

Certainly, other justices have been older than Rehnquist, and some have been much sicker.

Murphy recalled, for instance, seeing the late Justice William O. Douglas laboring through an oral argument in 1975, following a massive stroke. At one point, Murphy said, Douglas wrote a note but then lacked the strength to tear the piece of paper away from the pad.

“I had never seen a human being look so dead while still being alive,” said Murphy, who authored a recent biography of Douglas.

The legendary Oliver Wendell Holmes Jr. served on the court until he was 90. The less well-regarded Roger Taney was 80 when he authored the 1857 Dred Scott opinion declaring slaves property; he served on the court until he was 87. Rehnquist’s own colleague, Justice John Paul Stevens, is now 85.

But as history shows, the same lifetime tenure and insulation from voters that’s guaranteed by the Constitution can also lead some justices to serve well past their prime.

“The condition of the Supreme Court is pitiable, and yet those old fools hold on with a tenacity that is most discouraging,” President William Howard Taft, himself a former justice, wrote a friend in May 1909.

Taft further complained that the 76-year-old chief justice was “almost senile,” while a 71-year-old associate justice was “so deaf he can hardly hear;” two of the justices, Taft lamented, “sleep almost through all the arguments.”

Holmes, a Civil War combat veteran who was famously vigorous for decades, likewise faded away in a fashion that pained his many admirers.

“On the bench … the grand old man had great difficulty in keeping his head up and his eyes open,” author Merlo J. Pusey recounted in a detailed 1979 Supreme Court Historical Society report on disability among justices. “He would pile books in front of this face and go to sleep on the bench.”

Pusey, whose account also includes the 1909 letter from Taft, further detailed how friends and colleagues have periodically beseeched an aged justice into retiring. This can become dicey, as then-Justice Stephen Field recalled when asked in 1897 about the time he urged one of his aged fellow justices to retire.

“And a dirtier day’s work I never did in my life,” Field said, according to an account by former Chief Justice Charles Evan Hughes.

The public may not know for years, if ever, what kind of behind-the-scenes pleadings may be currently shaping Rehnquist’s plans. Certainly, there are some incentives to stay. With 34 years on the bench, Rehnquist is now closing in on Douglas’s record of 36 years. Moreover, Murphy suggested, the assistance of four law clerks _ Holmes, by contrast, had one _ combined with a declining case load lessens the burden of the job.

Still, Rehnquist’s physical infirmity has already been felt.

Diagnosed with thyroid cancer last fall, and now burdened with a tracheotomy tube, Rehnquist did not participate in oral arguments in November. Consequently, he did not vote in 11 out of the 80 cases considered by the court last term. All 11 cases were decided by margins in which Rehnquist’s vote would not have changed the outcome.