Vincent Bugliosi, a prosecutor who parlayed his handling of the Charles Manson trial into a career as a bestselling author, has died, his son said Monday night. He was 80 years old.

Bugliosi, who had struggled with cancer in recent years, died Saturday night at a hospital in Los Angeles, his son, Vincent Bugliosi Jr., told The Associated Press.

Bugliosi Jr. said his father had "an unflagging dedication to justice" in everything he did.

As an author, Bugliosi Sr. was best known for "Helter Skelter," which was his account of the Manson Family and the killings of pregnant actress Sharon Tate and six others by followers of the cult leader, Charles Manson.

Bugliosi had prosecuted Manson and his female followers, winning convictions in one of America's most sensational trials.

He was an unknown Los Angeles deputy district attorney on Aug. 9, 1969, when the bodies of Tate, the beautiful actress wife of Roman Polanski, and four others were discovered butchered by unknown assailants who left bloody scrawlings on the door of her elegant home.

The victims included members of Hollywood's glitterati: celebrity hairdresser Jay Sebring; coffee heiress Abigail Folger; Polish film director Voityck Frykowksi; Tate, who was 8 1/2-months pregnant; and Steven Parent, the friend of a caretaker.

A night later, two more mutilated bodies were found across town in another upscale neighborhood. The crime scene was marked with the same bloody scrawlings of words including, "Pigs" and "Rise" and "Helter Skelter." The victims were grocers Rosemary and Leno LaBianca, who had no connection to Tate and her glamorous friends.

Bugliosi was one of those assigned to the team of prosecutors while the case was being investigated. When members of the rag tag Manson Family were caught and charged with the crimes months later, a more veteran prosecutor, Aaron Stovitz, was named head of the district attorney's team and Bugliosi was assigned the second chair. But before long, a dispute arose between Stovitz and his boss over a remark he made to the media. He was summarily removed from the case and the intense, ambitious Bugliosi stepped into the role of a lifetime.

The trial of Manson and three female followers, Susan Atkins, Patricia Krenwinkel and Leslie Van Houten, lasted 9 1/2 months and became a courtroom drama that rivaled any cinematic trial. It cost Los Angeles County $1 million.

Bugliosi set the tone in his opening statement and closing argument, denouncing Manson as a murderous cult leader and his followers as young killers willing to do his bidding. He called the women "robots" and "zombies," manipulated by Manson -- "a dictatorial maharajah of a tribe of bootlicking slaves."

He first proposed the theory that Manson was inspired to violence by the Beatles song "Helter Skelter," which the cult leader thought predicted a race war that Manson and his followers would foment.

Determined to show the breadth of the Manson Family's reach, Bugliosi called 84 witnesses, most of them a parade of disaffected young people who joined up with Manson and fell under his sway.

The trial became an exploration of the cult and its drug and sex fueled adoration of Manson whom members venerated as Jesus. He introduced 290 pieces of evidence.

At times, the defendants sought to taunt the prosecutor, jumping up and singing in court or grabbing at his papers on his lectern. The trial went on for so long that a defense lawyer disappeared and was found dead in the woods. Bugliosi maintained there was foul play but none was found.

Bugliosi was born in 1934 in Hibbing, Minn. He attended the University of Miami at Coral Gables, Fla., on a tennis scholarship and graduated from the law school of the University of California, Los Angeles.

After the Manson trial, he wrote "Helter Skelter" with collaborator Curt Gentry, and it became one of the bestselling crime books of all time.

He tried running for public office and lost, tried his hand on practicing defense law but ultimately returned to writing books. He wrote a dozen books, including the true-crime books, "Till Death Do Us Part," and "And The Sea Will Tell."

His non-fiction efforts, which took on controversial subjects, included "Outrage: The Five Reasons Why O. J. Simpson Got Away With Murder," and "The Prosecution of George W. Bush for Murder."

Bugliosi Jr. said his father was most proud of his nearly 2,000-page examination of the Kennedy Assassination, "Reclaiming History," which took over 20 years to write.

But Bugliosi remained most associated with the Manson case for the rest of his life. Reflecting on it 40 years later, he said, "These murders were probably the most bizarre in the recorded annals of American crime. ... Evil has its lure and Manson has become a metaphor for evil."

Bugliosi and his wife of 59 years, Gail, had two children, Wendy and Vince Jr.