Lee Berry, a member of the Black Panther Party who was indicted in the largest case brought against that militant group, and whose personal plight helped inspire one of the most infamous New York social gatherings, a fund-raising party for the Panthers at the home of Leonard Bernstein that was mercilessly satirized by the writer Tom Wolfe, died on March 7 in a hospital near his home in Laurel, Md. He was 78.

The cause was anoxic brain injury, his daughter Afeni Berry said.

Mr. Berry was one of the Panther 21 — 19 men and two women who were charged in April 1969 with plotting to blow up Midtown Manhattan department stores, police stations and the New York Botanical Garden in the Bronx.

The case collapsed spectacularly two years later with the acquittal on all charges of the 13 defendants who were brought to trial. The District Attorney’s office had based its case on the testimony of undercover police informants, including a detective who had opened the Harlem branch of the Black Panthers in 1968.

Mr. Berry’s case was severed from that of the other defendants because he was in Bellevue Hospital when the trial began in February 1970.

It was his personal travail that prompted Felicia Bernstein, the wife of the New York Philharmonic maestro, to invite 90 guests to the couple’s Park Avenue apartment on Jan. 14, 1970, to raise money for the Panther 21 legal defense fund. Mr. Wolfe, a luminary of what was being called the New Journalism, wrote his takedown of the high-low soiree in New York magazine under the headline “Radical Chic: That Party at Lenny’s.”

He devoted many words to the canapés (“little Roquefort cheese morsels rolled in crushed nuts”) passed by liveried waiters to Panthers in Afros, dark glasses and black leather coats, all mingling with the director Otto Preminger, the band leader Peter Duchin, the socialite Cynthia Phipps and other A-list liberals in the Bernstein home, a 13-room penthouse duplex.

But the party might never have happened if Ms. Bernstein had not been at an earlier Panther fund-raiser the week before, at the home of the director Sidney Lumet, where Mr. Berry’s wife, Marva Berry, spoke about her husband’s ordeal behind bars.

An Army veteran, Mr. Berry, then 24, was being treated for epileptic seizures at a Veterans Administration Hospital when he was indicted. After his mother told him that the police were looking for him, he called to tell them where to find him. Officers rousted him from his hospital bed in handcuffs and took him to the Manhattan Detention Complex, known as the Tombs, according to the account Ms. Berry gave at the Lumet home.

“It was this statement, which went on to allege that her husband was beaten in the Tombs, denied proper medication and held for seven months before being transferred to Bellevue, that prompted Mrs. Bernstein to consult with some civil rights lawyers and then invite friends in to hear more about the case,” wrote Charlotte Curtis, a society reporter for The New York Times, who covered the Bernsteins’ party.

“I was shocked,” Ms. Bernstein told The Times about Ms. Berry’s account. “I couldn’t believe anyone could have been treated so inhumanely.”

At one point during the party Ms. Berry tried to comfort a rich white woman who worried that she and her capitalist husband would be killed when the revolution came. “Oh, no,” Ms. Berry said. “You sound as if you’re afraid. Now, there’s no reason for that.”

In a federal lawsuit over the Panthers’ pretrial confinement, defense lawyers claimed that Mr. Berry was beaten by a jail guard for refusing to stand for a prisoner count and was denied treatment for his epilepsy. The Department of Correction denied the accusations.

Mr. Berry was transferred from the Tombs to Bellevue Hospital in November 1969. After a hearing in the hospital, his bail was reduced from $100,000 to $15,000 in April 1970, and he soon walked free.

The charges against him were eventually dropped.

Leo Stanley Berry was born on Jan. 16, 1946, in Brooklyn to Leo Berry, who had moved north from Georgia as part of the Great Migration of African Americans seeking a better life, and Elizabeth (Rizer) Berry, who had moved from Florida. His father left the family when Lee was 6. He was raised in the Cypress Hills Housing Project in the East New York neighborhood and attended Lane High School.

Mr. Berry joined the Army in 1964 and spent two years in Germany before being medically discharged because of a seizure disorder, according to his family. He married and had a daughter, but the couple soon separated and later divorced.

Mr. Berry met Marva Kirton in Brooklyn in 1968, just before the assassination of the Rev. Dr. Martin Luther King Jr. After Dr. King’s murder, founders of the Black Panthers from the West Coast visited the campus of Long Island University to organize a New York Panther branch. Mr. Berry was an early recruit. (Another early member was Afeni Shakur, one of the two women indicted with the Panther 21; she was the future mother of the rap star Tupac Shakur.)

“That was a pivotal moment when people were feeling a very strong loss of hope,” Ms. Berry, who became a public-school teacher in New York and Washington, recalled in a recent interview. “Lee and a lot of people after Dr. King was killed, they had had enough.”

Before joining the Panthers, Mr. Berry had demonstrated in support of Black local control of the public schools in the Ocean Hill-Brownsville district in Brooklyn, after administrators there fired 12 Jewish teachers, triggering a citywide teachers’ strike.

The national Black Panther Party was founded in 1966 in Oakland, Calif. Its early members carried loaded rifles to protect against police brutality, while also demanding, in a 10-point program, jobs, housing and schools “that expose the true nature of this decadent American society.”

The Panthers’ militancy was met by an F.B.I. campaign to destroy the organization, in part by pitting factions against one other. Violent encounters with the police and with other Black nationalist groups in the late 1960s and early ’70s claimed numerous lives.

During the Panther 21 trial, the home of the presiding judge, John M. Murtagh, was firebombed, causing damage but no injuries.

Two of the Panther 21 defendants were later convicted of roles in the notorious 1981 robbery of a Brink’s armored car in Rockland County, N.Y., which left a guard and two police officers dead.

One of the men, Donald Weems, also known as Kuwasi Balagoon, died in prison. The other, Edward L. Joseph, also known as Jamal Joseph, served five and a half years in prison and is now a professor at Columbia University.

Mr. Berry became a commercial photographer with a storefront business in East New York. He and his wife and their numerous children were known in their neighborhood, where they drove a yellow station wagon, as the Berry Bunch. The couple divorced in the 1990s.

In addition to his daughter Afeni, Mr. Berry is survived by six other children, Nicole Hall, Jemyl Lindsay and Safonia, Shaka, Chad and Niger Berry; seven grandchildren; one great-grandchild; and a brother, Tom.

A grandson, Christopher Lindsay, dramatized Mr. Berry’s imprisonment in a play, “Songs of a Caged Bird,” which was performed online in 2021 while Mr. Lindsay was a graduate student at Brown University.

Despite the mockery heaped upon the Bernsteins and other rich New Yorkers who feted the Panthers in 1970, Marva Berry said that she had not felt condescended to, and that the evenings raised awareness of the Panther 21 when not many people were paying attention.

“It was a very welcoming event,” she said of the Bernstein party. “It was a changing time in history, where people were moving from one level to the next.”