LOS ANGELES, Oct. 5 — Paul J. Fitzgerald, a pugnacious former public defender who became the lead defense attorney in the bizarre 1970 murder trial of cult leader Charles Manson and his followers, has died. He was 64.

He was found dead by an associate Tuesday at his Beverly Hills home. He had suffered from heart problems for many years and died of an apparent heart attack, his family said.

Fitzgerald was legendary in the legal defense community. As a Los Angeles County public defender in the mid-1960s, he wrote training manuals that led to enduring practices in such key areas as the questioning of prospective jurors.

He shared his knowledge of murderers, pimps and other unsavory Los Angeles characters with writer John Gregory Dunne, whose 1982 bestseller, “Dutch Shea, Jr.,” was inspired in part by Fitzgerald and his bounty of incredible cases.

“The law,” said Dunne, “was deadly serious business for him. He defended some of the worst people in the world … and he made no apologies for it.”

He mentored members of the criminal defense bar, including now-prominent Los Angeles lawyers Leslie Abramson and Gerald Chaleff, and was a founder of California Attorneys for Criminal Justice, a defense bar association.

He also was highly respected by his opponents. “He was an outstanding trial lawyer,” said veteran prosecutor Stephen Kay, who faced off against Fitzgerald during the grueling, often surreal months of the Manson trial.

In news photos from the late 1960s, he looks up in a boxer’s pose, chin down but eyes up. His face, Dunne recalled, had a “punched-in quality.” If his nose looked broken, it probably was. The second of seven children in an Irish American family, he was a Golden Gloves champ as a teenager in Minneapolis.

He majored in political science and minored in philosophy at the University of Minnesota, where he earned a law degree in 1964. That year he moved to California with his wife, and soon joined the public defender’s office in Los Angeles.

Decades before jury selection consulting became a highly remunerated field, he wrote a guide for public defenders on how to question prospective jurors and uncover their biases that remains a staple in training and practice. “He was in the vanguard,” said Los Angeles County Chief Public Defender Michael Judge.

Fitzgerald rose rapidly, and was assistant chief trial deputy when he became the lawyer for Patricia Krenwinkel, one of three Manson followers accused in the brutal August 1969 killings of actress Sharon Tate, Los Feliz grocery chain owner Leno LaBianca and his wife, Rosemary, and four others.

But when Fitzgerald’s superiors discovered that the office previously had represented others involved with Manson — a conflict of interest — Fitzgerald was told he would have to give up the case. He refused.

“He felt [Krenwinkel’s] role in the events was as a victim of brainwashing by Charles Manson,” recalled Abramson, then a clerk in the public defender’s office. “He felt a tremendous responsibility to keep defending her.”

The only way he could do that was by resigning. Krenwinkel was not only a nonpaying client, she was his only client. The job caused financial hardships for the lawyer, who by then was the father of two small children.

The next seven months brought sensational testimony — often with gut-turning twists — and nightmare moments for the defense.

Vincent Bugliosi, the original lead prosecutor, wrote disparagingly of Fitzgerald’s courtroom performance in his 1974 book “Helter Skelter,” calling the attorney’s arguments “disappointing” and suggesting that he bungled Krenwinkel’s chance to “beat the rap.”

Others discounted Bugliosi’s criticism.

Fitzgerald was, by most accounts, the mainstay of a somewhat motley defense crew. One lawyer had no criminal experience. Another was famous for his obstructionist tactics, reportedly objecting once to a witness giving his mother’s name because that would be hearsay.

All four defendants — Manson, Krenwinkel, Susan Atkins and Leslie Van Houten — were convicted and sentenced to death, which later was changed to life in prison when the death penalty was overturned.

The worst moment for Fitzgerald came during the penalty phase, when his client joined Atkins and Van Houten in confessing, in horrifying detail, that they and Tex Watson, another Manson clan member, had killed the victims. “It was devastating,” Deutsch recalled. Fitzgerald looked shellshocked, even though he had been warned of their plan by the women.

Fitzgerald later represented Krenwinkel and Van Houten in parole hearings. “He thought Krenwinkel’s story was very tragic — a middle-class, normal, nice girl who, through the use of drugs and basic brainwashing, turned into a killer and accessory to murder,” Abramson said.

He never had another case as spectacular. He remained in private practice, representing scores of unsympathetic characters. He was so colorful in his descriptions of some of his cases that Dunne appropriated his language word for word for parts of “Dutch Shea, Jr.” such as a line about a cunning pimp as “our municipal wart.”

Fitzgerald was a sought-after lecturer, especially on the topic of defending the hopeless case.

But, said Chaleff, “I don’t think there was a hopeless case to Paul. He believed the state had to prove its case. There was a purity about him … a view that what he was doing was important and beneficial to everyone; it protected society. He was one of those lawyers who, if Paul was on the case, the person was going to get a good defense.”

He is survived by his two daughters, Teresa Nersesyan of Tujunga and Elizabeth Simonian of Lake Tahoe; five grandchildren; three brothers; and two sisters.

A viewing will be held from 5 to 7:30 p.m. Thursday at Pierce Bros. Mortuary in Westwood. The funeral will be held at 9:30 a.m. next Friday at Church of the Good Shepherd in Beverly Hills.

By ELAINE WOO