Dave Toschi, a dapper cop who became the lead San Francisco police investigator for the Zodiac serial-killer case in the late 1960s and ’70s, has died at the age of 86.

Toschi died at his home in San Francisco on Saturday after a lengthy illness, relatives said.

The Zodiac terrorized the Bay Area in 1968 and 1969 when he stabbed or shot at least five people to death, writing taunting notes and cryptograms to police and newspapers including The Chronicle after his kills. Toschi was drawn into the case when he was assigned to investigate the killing of the Zodiac’s only San Francisco victim — Paul Stine, a cabbie shot to death in his taxi on Oct. 11, 1969.

It was the Zodiac’s final confirmed slaying. Like every other inspector looking into the saga, from federal agents to police in Vallejo and Napa County, Toschi was unable to solve the case. But he never lost zeal for the mystery, friends said.

He was a super guy and a great cop,” said Duffy Jennings, who covered the Zodiac case as a Chronicle reporter in the 1970s and maintained a lifelong friendship with Toschi afterward. “And he told me that he still went every year on Oct. 11 to the Paul Stine murder scene to look around and try to figure out why they couldn’t catch the guy.

“The Zodiac case gnawed at him,” Jennings said. “He said it gave him an ulcer.”

Toschi was born in San Francisco and, after graduating from Galileo High School, he pulled combat duty in the Korean War with the Army. Upon his return to San Francisco in 1953, he was hired at the Police Department and stayed there until retiring in 1985.

In addition to his work on the Zodiac killings, Toschi was part of the team that solved the racially motivated Zebra murders in the early 1970s, in which four black men were convicted of the random slayings of 14 white people. In 1985 he received a meritorious conduct award from the department for arresting a man who raped senior citizens and burglarized their homes

His penchant for bow ties, snappy trench coats and the quick-draw holster for his .38-caliber pistol drew the attention of Steve McQueen, who patterned his character in the 1968 movie “Bullitt” after Toschi. Clint Eastwood’s “Dirty Harry” character was also partially inspired by him.

But it was the Zodiac case for which Toschi was best known. He worked the clues until 1978, when he was taken off the case after admitting he sent fan notes with fictitious names to then-Chronicle writer Armistead Maupin praising himself. Toschi told the San Francisco Examiner that the notes were an “ill-advised indulgence.”

In the brouhaha that resulted, there were suspicions that he might have also written a letter to The Chronicle that purported to be from the Zodiac. However, nothing was proved, Toschi denied it and he remained with the department as a homicide inspector until his retirement. He was portrayed by Mark Ruffalo in the 2007 movie “Zodiac.”

“I always looked up to him because he was this Italian guy who got this crazy case,” said Gianrico Pierucci, who retired in November after being the latest in a long line of homicide inspectors to head up the still-alive Zodiac investigation. “He was a good cop. He said he was always happy to get up and do his job.”

Of the Zodiac case, Pierucci said: “Dave did the best he could. He was always very pleasant and charming, and dapper, and Zodiac is a tough case.”

After leaving law enforcement, Toschi worked in the security business, including several years as vice president of Northstar Security Services.

“He loved books, music and could sing with the best of them,” said his daughter, Linda Toschi-Chambers of San Francisco. “His greatest pleasure was his loving family, and we will miss his keen sense of humor, his gentle guidance and his unconditional love.”

Toschi is survived by his wife, Carol Toschi of San Francisco; two daughters, Toschi-Chambers and Karen Leight of San Mateo County; and two granddaughters, Sarah Leight of Pacifica and Emma Leight of Los Angeles.

Private services were held Wednesday. Donations may be made in his name to St. Jude Children’s Research Hospital in San Francisco, or to a charity of choice.

Kevin Fagan is a San Francisco Chronicle staff writer. Email: kfagan@sfchronicle.com Twitter: @KevinChron

David Ramon Toschi