It was in the last role that he had his greatest success.
The task force worked out of FBI headquarters in Philadelphia. Collaborating with investigators from the Pennsylvania and New Jersey state police forces, the unit took on Nicodemo "Little Nicky" Scarfo, then the region's reputed head of organized crime, by creating a network of informants.
In 1988, the task force's efforts paid off when Scarfo and 16 associates were convicted of racketeering and conspiracy charges and were sentenced to prison. The killings stopped.
In 1989, Mr. Friel told Inquirer reporter Thomas J. Gibbons Jr.: "There hasn't been a mob murder since 1985, so we're pretty convinced we got the right guy in Scarfo."
Michael J. Chitwood, Upper Darby public safety superintendent, was a homicide detective in Philadelphia when Mr. Friel was a lieutenant.
"I knew Frank Friel for years," Chitwood said. "He was an intelligent, articulate, hardworking guy." Chitwood said it would not be exaggerating to say that Mr. Friel and the task force brought the local mob to its knees.
Gibbons, a police officer who became a journalist, recalled Mr. Friel as personable and flexible. "He could interact with all kinds of people, be it law enforcement or the bad guys, and through that, he could bring these cases to a successful conclusion," Gibbons said.
George Anastasia, who covered the mob for The Inquirer before retiring in 2012, said Mr. Friel was the catalyst for a change in the agenda among law enforcement agencies tracking mob crime.
Before his involvement, the agencies had withheld information from one another as they competed for credit. After he became involved, "it was about getting a result and not getting credit," Anastasia said. "It would not have happened without him."
In 1989, just before he was scheduled to be promoted to inspector, Mr. Friel turned in his retirement papers and became director of public safety in Bensalem.
Mr. Friel led the Bensalem force from January 1989 to April 1996. He came at a time when the department was fractured with office politics.
Mr. Friel, as an outsider, ended that and brought a new level of professionalism to the department. He also was the first chief to draw up policies and procedures that officers had to follow, said Pat Ponticelli, deputy public safety director.
"The knowledge that he had, working in a big-city department, helped shape our department that was growing at the time," Ponticelli said.
While Mr. Friel put many criminals behind bars, he was instrumental in setting an innocent man free.
Neil Ferber had been sentenced to death for the May 27, 1981, murders of reputed mobster Chelsais "Steve" Bouras and his dinner guest, Jeanette Curro, at Meletis Restaurant in South Philadelphia.
Mr. Friel became convinced that Ferber was not guilty and developed evidence that he presented to District Attorney Ed Rendell, who eventually was persuaded to request a new trial. Ferber's conviction was overturned Jan. 3, 1986, and the charges were later dropped.
Dennis J. Cogan, Ferber's appellate lawyer, recalled Tuesday that Mr. Friel was under a lot of pressure in the Police Department to leave the case alone, but that refused to back down.
"He was an uncommon champion of the truth," Cogan said.
The one career setback Mr. Friel experienced was in 2004. Rendell, by then governor, had appointed him chairman of the Pennsylvania Gaming Control Board. But Mr. Friel quit after a month when questions were raised about his academic credentials.
Rendell defended him, but the resignation stood. "Sadly, a media sideshow in this case has unfairly tarnished the reputation of a good and decent man," Rendell said.
The blip on his record did not deter Mr. Friel, who lectured widely at conferences organized by law enforcement agencies.
His book, Breaking the Mob, was published by McGraw-Hill in 1990 and republished by Warner Books in 1992.
Mr. Friel was chairman of the board of the Vidocq Society, which investigates cold cases.
His wife, Kathleen, said the couple enjoyed fishing, boating, and "just a lot of fun" at their second home in Myrtle Beach, S.C. She said he was a dog lover and "a good husband, father, and friend."
Surviving, besides his wife of 17 years, are daughters Rosemary Friel and Melissa Hoover; sons Timothy Friel and Jeffrey Hoover; three grandsons; a brother; and his former wife, Ida.
Friends may call at 10 a.m. Monday, Jan. 13, at St. Ephrem Roman Catholic Church, 5400 Hulmeville Rd., Bensalem. A funeral service will follow at 11. Burial is private.
Donations may be made to Bridge to Healing, c/o Alliance Cancer Specialists, St. Clare Medical Building, 1203 Langhorne-Newtown Rd., Suite 135, Langhorne, Pa. 19047.
Inquirer staff writers Ben Finley and Robert Moran contributed to this article.