Gerald Shargel, who unapologetically vowed to “do anything that the law will allow” to defend the Mafia bosses, crooked politicians and other miscreants he represented for more than four decades as a savvy criminal lawyer, died on Saturday at his home in Manhattan. He was 77.

The cause was complications of Alzheimer’s disease, his wife, Terry Shargel, said.

More often than not, Mr. Shargel combined cogent legal scholarship with shrewd courtroom theatrics to vindicate a roster of white collar clients and Mafioso — including John Gotti, Anthony Provenzano, Joseph Gambino and Salvatore Gravano — whom the gregarious Mr. Shargel not only represented but befriended.

“Suffice it to say he put the Teflon in the Don,” Geraldo Rivera, the television journalist and Mr. Shargel’s former classmate at Brooklyn Law, said in an email, referring to Mr. Gotti’s moniker.

Mr. Shargel said that being accorded entree to mob sanctums like Mr. Gotti’s Ravenite Social Club in Manhattan’s Little Italy was “cool because it’s like a movie.”

He got so close to some Mafia clients that a federal district judge, I. Leo Glasser, removed him from representing one mob figure after prosecutors accused him of serving as “house counsel” to an organized crime family, an allegation he denied.

Mr. Gotti himself got upset with Mr. Shargel, for being too talkative to reporters: Mr. Gotti was caught on a wiretap warning, “I’m gonna show him a better way than the elevator out of his office” (which was on the 32nd floor).

The message was encapsulated in a front-page headline in The Daily News on April 3, 1991: “Shaddup.”

On other tapes, Mr. Gotti referred to the lanky, bearded Mr. Shargel as “an errand boy” and was overheard boasting: “Jerry said, ‘Listen, John. You know I got one love — you.’”

But in the legal profession Mr. Shargel was admired for his courtroom acumen. “He was the best criminal lawyer of his generation,” said Joan Wexlerthe former president and dean of Brooklyn Law School, his alma mater.

Former US District Judge John Gleeson, who as a federal prosecutor was one of Mr. Shargel’s chief adversaries, said, “What distinguished him most was he not only knew his case inside out and could plan a great defense strategy, but he was so disciplined.”

Judge Gleeson added that while his successful motion to disqualify Mr. Shargel from the defense in a mob trial “is a matter of public record and speaks for itself, it does nothing to undermine the common ground and friendship Jerry and I found later in our careers.”

As a canny courtroom tactician, Mr. Shargel subjected the prosecution to the most cross-examination, peppering them with sarcastic zingers that undermined their credibility and charmed juries.

When one witness explained that the accessories required for a mob induction included not only a needle to draw blood for the ritual oath, but also a bottle of alcohol to sterilize the pinprick, Mr. Shargel asked mordantly, “In other words, you were going to get into the Mafia, but you didn’t want to infect your finger?”

Mr. Shargel’s clients included murder defendants and a host of white collar criminals.

Among them were Nicholas Barbato, the former Republican boss of Smithtown, NY, who was acquitted in 1981 of taking $267,000 in bribes from a Long Island sewer contractor; and Stanley M. Friedman, a former New York City deputy major and Bronx Democratic leader and a mastermind of scandals during the 1980s, who was convicted in a separate state case but spared and additional prison term in 1991.

Mr. Shargel also represented the hip-hop impresarios Irv and Chris (Gotti) Lorenzo (known as the Gotti brothers) who were accused of money-laundering drug profits through their record label, Murder Inc. They were acquitted.

Chris Lorenzo recalled that Mr. Shargel had demanded the truth from the two brothers before mounting their defense, saying: “You have to make the snowballs. I’ll throw them.”

“Jerry could move a jury emotionally and also had a total command of the law,” said Judd Burstein, who was briefly his law partner. “It was an extraordinary combination. And his style was unique because of his ability to speak to judges with an eloquent passion which made them want to believe him.”

“He was never ashamed of all those mobsters because a criminal lawyer represents criminals,” Mr. Burstein said.

Mr. Shargel argued that he was no more aggressive in defending his clients than the government was in prosecuting them.

Referring to the extortion and robbery case against John Gotti Jr., a son of the reputed mob boss, Mr. Shargel told The New York Times in 1999: “The government’s campaign reminded me of something that Gregory Scarpa” — a deceased member of the Colombo crime family — “once was heard to say. After he killed a particular person, he was heard saying that he hated the guy so much that he wanted to dig him up and kill him again. The government hates John Gotti, the father, so much that they’re trying him again, through his son.”

“Clients hire me,” he told The New Yorker in a 1994 profile, “because I’ll do anything that the law will allow, without concern for how it’s gonna make me look.”

Gerald Lawrence Shargel was born on Oct. 5, 1944, in New Brunswick, NJ His father, Leo, owned a paint and wallpaper store. His mother, Lillian (Edenzon) Shargel, was a secretary in the math department at Rutgers University.

After graduating from Bound Brook High School in New Jersey, he earned a degree in history from Rutgers and graduated from Brooklyn Law School in 1969. He was later a professor there.

During law school, he interned with the United States Attorney’s office in Brooklyn, his only direct exposure to the inner workings of a prosecutor’s office.

Sitting in on a trial, though, he became enamored with the case presented by James LaRossa, a prominent defense lawyer. He joined Mr. LaRossa’s firm after law school, working there until 1976. He then practiced as Shargel Law until 2013 and became a partner in Winston & Strawn until 2018.

In addition to his wife, who was Terry Krapes when they married, he is survived by their daughter, Johanna Tobel; their son, David; six grandchildren; his mother, and his sister, Judy Shargel.

Mr. Shargel once said he was appalled by some of the violent crimes his clients were accused of committing, but he argued that defense lawyers should not be motivated by whether the defendants they represent were guilty.

“A lot of clients tell me they’re innocent, because they think I’ll work harder for them,” he told The New Yorker. “That’s not true. It’s irrelevant. The question is: Can the state prove its case?”

Benjamin Weiser and Alan Feuer contributed reporting.