“I haven’t really thought much about it,” he said when asked about his first day as a private citizen. “I’ll probably have a nice cup of coffee.”

His fans have responded to his retirement with more fanfare, including an evening in early November when thousands of lawyers, judges, law enforcement officials and legislators filed into the Jacob Javits Center to pay tribute to the man they call “The Boss.”

Guests were treated to a slideshow of Morgenthau’s illustrious life, which included a photo of a much younger Morgenthau serving a mint julep to Franklin Roosevelt, as well as a proclamation from Gov. David Paterson commending Morgenthau for his long service and a video message from Supreme Court Justice Sonia Sotomayor, one of the many famous Morgenthau alums.

“There were people that were current assistants, there were people who were assistants 30 years ago,” said Staten Island District Attorney Dan Donovan, another alum. “It was just a remarkable event.”

But seated in his office, surrounded by boxes of old documents and piles of framed photographs and awards, some sporting post-its written by his wife that read “Property of RMM,” Morgenthau said his focus is on what he calls his main source of pride.

“The important thing was to investigate cases without fear or favor, without any outside influence, totally independent,” said the 90-year-old district attorney. “You want the public to have confidence in law enforcement and in order to do that, you got to be impartial [and] fair.”

But even after over three decades in office, Morgenthau said he has no intention of retiring peacefully to his 300-acre farm upstate.

“I’ll probably be involved in practice of law,” he said. “I’m not going to fade away.”

He spoke of possibly looking for work in immigration law or the enforcement of economic sanctions against Iran, a cause he says has major implications for national and international security. He also plans to continue serving as chair of the Police Athletic League (a position he has held since 1962) and of the Museum of Jewish Heritage.

Morgenthau will be remembered for his many civic accomplishments, but his former aides say his revolutionary approach to prosecuting crime will likely be his most enduring legacy.

Dan Castleman, Morgenthau’s former top deputy who was passed over in his quest to succeed his boss in favor of Cy Vance, pointed to the “vertical model” of prosecution as Morgenthau’s great accomplishment—carrying over the method of the United States attorney’s office, he discarded the more conventional, assembly-line approach toward criminal prosecutions that the office had used.

“When you touch a case, it becomes yours from start to end,” Castleman said. “It made it infinitely better for everyone involved.”

Many district attorneys’ offices around the country now use the vertical model.

Morgenthau was also aggressive when it came to asserting his authority over cases that fell outside his jurisdiction. Randy Mastro, a prosecutor and former deputy mayor under Rudy Guiliani, said Morgenthau displayed this tendency when prosecuting Guy Velella, the former Bronx state senator’s whose political corruption case might normally have been convicted by either the Bronx or Albany district attorneys.

“Intuitively it doesn’t make a lot of sense,” Mastro said. “But it shows just how he creative in asserting his jurisdiction he could be.”

Current and former aides say Morgenthau was adept at protecting his staff from external political pressures. But some say he will also be remembered for hiring the sons and daughters of the wealthy and powerful. Morgenthua’s preference for Vance, the son of a former secretary of state, in the race to succeed him was seen by some an extension of that tendency.

Then, in the last few weeks in office, there was the very public feud between Morgenthau and Mayor Michael Bloomberg over the existence of several secret bank accounts containing almost a hundred of million dollars. Morgenthau would not say he was disappointed the blowup came so close to the end of his tenure as DA, but said his disagreement with the mayor was about much more than money.

“It really was a dispute over power,” Morgenthau said. “He didn’t like the idea that there was an independently elected district attorney that didn’t report to him.”

After initially telling a reporter that Bloomberg’s accusations amounted to “chicken shit,” Morgenthau was more tight-lipped about his occasional opponent the mayor.

“I’ve been forbidden to use barnyard epithets by my wife,” he said.

Especially in front of his grandson, who sat quietly off to the side, waiting stake his claim on some of his grandfather’s more prestigious office knickknacks. Of course, any family member will have to contend with archivists from the Roosevelt Library and the Museum of Jewish Heritage, who plan on going over Morgenthau’s mementos with a fine-toothed comb.

Looking wistfully at some World War II-era photos of himself standing on the deck of a battleship, Morgenthau briefly considered which was a more challenging period: four-and-a-half years in the Navy or 35 years as Manhattan DA.

“Not even close,” he said, smiling. “It was more exciting in the Navy.”