Robert Morgenthau has been cast in many roles during his decades in office.

The inspiration for the district attorney on TV's "Law & Order." A taker-on of mobsters, misbehaving celebrities and corrupt CEOs. A Democratic powerbroker who grew up among Roosevelts and Kennedys and helped launch careers, including U.S. Supreme Court Justice Sonia Sotomayor's.

A local prosecutor who used his office's prominence to stretch the long arm of the law where he saw fit. A savvy, wry and indefatigable New York institution who happens to be 90.

In short, "DA for life."

But Morgenthau closes the curtain Thursday on his 35 years as Manhattan district attorney with little time for reminiscing. In the last week of his term, he was still holding news conferences to announce a flurry of prosecutions and guilty pleas.

"You think I'm going to go quietly?" he joked.

Morgenthau is stepping down from one of the nation's biggest and most prestigious prosecutor's offices, with about 500 lawyers handling 100,000 cases a year. As Manhattan's top federal prosecutor for eight years before being elected as the borough's DA in 1974, he symbolized the criminal justice system for generations of New Yorkers, not to mention TV viewers.

"Law & Order" creator Dick Wolf calls Morgenthau "the greatest district attorney in the history of New York" and used him as the template for pragmatic-but-principled DA Adam Schiff, played by actor Steven Hill in the series' first decade.

Sotomayor, one of Morgenthau's former assistant prosecutors, said in videotaped remarks for a recent event honoring him that he "set a standard of unparalleled prosecutorial excellence and integrity."

Morgenthau quipped in a recent interview with The Associated Press that he's retiring because, "I looked at my birth certificate, and I said, 'It's about time.'"

In other words, his departure, like his tenure, is very much on his own terms.

Morgenthau is hard of hearing and walks slowly but otherwise shows few symptoms of his age. He also remains a key player in the city's legal and political scenes. After handily defeating a former judge who tried to unseat him in 2005, Morgenthau helped his chosen successor, defense lawyer Cy Vance, beat the same jurist and a third contender this year. Vance, one of Morgenthau's assistant prosecutors in the 1980s, has pledged to build on Morgenthau's "outstanding legacy," though he already has shaken up the office's top staff.

The caseload reads at times like an awards-show guest list: A single morning in 2007 brought rappers Busta Rhymes, Ja Rule and Remy Ma to court in separate cases.