Dunne’s son, Griffin Dunne, said in a statement released by Vanity Fair magazine that his father had been battling bladder cancer. But the cancer had not prevented Dunne from working and socializing, his twin passions.

In September 2008, against his doctor’s orders and his family’s wishes, Dunne flew to Las Vegas to attend Simpson’s kidnap-robbery trial, a postscript to his coverage of the football great’s 1995 murder trial, which spiked Dunne’s considerable fame.

In the past year, Dunne had traveled to Germany and the Dominican Republic for experimental stem cell treatments to fight his cancer. He wrote that he and actress Farrah Fawcett were in the same clinic in Bavaria but didn’t see each other. Fawcett, a 1970s sex symbol and TV star of “Charlie’s Angels,” died in June at age 62.

Dunne discontinued his Vanity Fair column to concentrate on finishing another novel, “Too Much Money,” which is to come out in December. He also made a number of appearances to promote a documentary film about his life, “After the Party,” which was being released on DVD.

Dunne, who lived in Manhattan, was beginning to write his memoirs and until recently had posted messages on his Web site commenting on events in his life and thanking his fans for their support.

Vanity Fair editor Graydon Carter praised Dunne as a gifted reporter who proved as fascinating as the people he wrote about.

“Anyone who remembers the sight of O.J. Simpson trying on the famous glove probably remembers a bespectacled Dunne, resplendent in his trademark Turnbull & Asser monogrammed shirt, on the court bench behind him,” Carter wrote in a statement released Wednesday. “It is fair to say that the halls of Vanity Fair will be lonelier without him and that, indeed, we will not see his like anytime soon, if ever again.”

Earlier this summer, Dunne was well enough to attend a Manhattan party hosted by Tina Brown. Chatting with an Associated Press reporter, he spoke of Michael Jackson, who recently had died, and remembered lunching with the singer and Elizabeth Taylor. Jackson was so excited to see her, Dunne said, he presented her with a diamond necklace just for the occasion.

Dunne was part of a famous family that also included his brother, novelist and screenwriter John Gregory Dunne; his brother’s wife, author Joan Didion; and his son Griffin.

A one-time movie producer, Dunne carved a new career starting in the 1980s as a chronicler of the problems of the wealthy and powerful.

Tragedy struck his life in 1982 when his actress daughter, Dominique Dunne, was slain – and that experience informed his later fiction and journalistic efforts.

“If you go through what I went through, losing my daughter, you have strong, strong feelings of revenge,” Dunne said in 1990 in discussing his novel “People Like Us,” in which the protagonist shoots the man convicted of killing his daughter.

“I intended for Gus (the character in the book) to kill the guy. But when I got to that part I couldn’t write it. He wounds him and goes to prison himself for a couple of years,” Dunne said.

He was as successful a journalist as he was a novelist and spent many of his later years in courtrooms covering high profile trials. Writing for Vanity Fair, he covered such cases as the William Kennedy Smith rape trial in 1991 and the trial of Erik and Lyle Menendez, accused of murdering their millionaire parents, in 1993.

As riveting as those trials were, they were far overshadowed in 1994, when Simpson was accused of killing his ex-wife Nicole Brown Simpson and her friend Ronald Goldman. With a trial that stretched out over a year and cable TV outlets providing endless coverage, Dunne became a familiar face to millions.

“I especially like to watch the jurors,” Dunne explained to Fox TV during the trial. “I always pick out about four jurors who become my favorites. I sort of try to anticipate what they are thinking and how they are reacting.”

He called his book on the Simpson trial, “a novel in the form of a memoir.” It, too, became a best seller.

From the gritty world of the courtroom during the day, he would move into the glamorous realm of high society at night, dining with the rich and famous, charming them with his inside stories of the Simpson trial.

He was a colorful raconteur and his stories mesmerized listeners. He was a much sought after dinner guest on both coasts and in the glamour capitals of Europe, where he frequently traveled. He was a regular at the Cannes Film Festival, interviewing members of royalty and movie stars.

His assignments took him to London to cover the inquest into Princess Diana’s death and to Monaco to look into the mysterious death of billionaire Edmond Safra.

He continued appearing regularly on television, and in 2002 debuted a weekly program on Court TV, “Power, Privilege and Justice.” The show gave him an added dose of celebrity when it was distributed in foreign countries.

He had already been working on “The Two Mrs. Grenvilles,” a fictionalized retelling of a sensational 1950s society murder, when his 22-year-old daughter was strangled by her former boyfriend, John Sweeney, shortly after she had completed her first movie, “Poltergeist.”

Sweeney was convicted of voluntary manslaughter, not murder, and was freed after serving less than four years of a six-year sentence. The verdict was seen as a major victory for the defense, and Dunne bitterly told the judge in court, “you withheld important information from this jury about this man’s history of violent behavior.” He later told the Los Angeles Times the sentence was “a tap on the wrist.”

In a 1985 AP interview, Dunne said he nearly stopped writing when his daughter was slain because he didn’t want to do a book that dealt with murder, but his editor wouldn’t let him quit.

“She was incredibly sympathetic and lenient on time,” he said. “I’m glad now that she didn’t let me quit.”

Among his other books were the 1993 “A Season in Purgatory,” which helped revive interest in the 1975 slaying of teenager Martha Moxley in Greenwich, Conn. A Kennedy relative, Michael Skakel, was convicted in the killing in 2002.

Dunne also wrote “An Inconvenient Woman” and “The Mansions of Limbo.”

In 1999, Dunne published a memoir called “The Way We Lived Then,” a compilation of photographs of him and his family with famous people and his recollections of the glamour life he and his wife enjoyed for many years.

Dunne was born in 1925 in Hartford, Conn., to a wealthy Roman Catholic family and grew up in some of the same social circles as the Kennedys. The memoir traced his fascination with Hollywood to a childhood trip he took “out West” with an aunt. They took one of those homes of the stars bus tours and he vowed to come back and be part of the glamorous world he had glimpsed.

He served in the Army during World War II and was awarded the Bronze Star for heroism in 1944 for carrying two wounded men to safety at the Battle of Merz in Feisberg, Germany. “Winning a medal was the only thing I can ever remember doing that won any admiration from my father,” he later wrote.

At Williams College in Massachusetts, he and a fellow student, Stephen Sondheim, appeared in plays together. After graduating in 1949, he went to New York where he landed a job in the fledgling TV industry as stage manager of the “Howdy Doody” show. NBC took him to Hollywood to stage manage the TV version of “The Petrified Forest” with Humphrey Bogart.

Among his producer credits were the TV series “Adventures in Paradise” and “The Boys in the Band,” a pioneering 1970 drama about gay life. His brother and sister-in-law co-wrote two of his films, “The Panic in Needle Park” and “Play It As It Lays.”

Dunne and his wife, Ellen Griffin Dunne, known as Lenny, were married in 1954. They divorced in the 1960s but he wrote that afterward they remained close nonetheless. She died in 1997.

Beside Dominique, they had two sons, Alexander and Griffin. Griffin has acted in such films as “An American Werewolf in London” and “After Hours.” He branched into directing and producing, with “Fierce People” and “Practical Magic” among his credits.