He went to federal prison in 1987, convicted of running a sports gambling operation and laundering proceeds through a Philadelphia brokerage house. The money-laundering charges later were overturned.
But 18 months in prison didn't persuade Mastronardo, 41, to change careers.
On Tuesday, federal prosecutors will go before U.S. District Judge James T. Giles seeking to have Mastronardo's probation revoked. They will introduce extensive wiretap evidence to bolster their claim that "Joe Vito" - as Mastronardo is known to associates - once again is heading an interstate sports betting ring.
Mastronardo - the son-in-law of Frank Rizzo - could return to jail for up to five years on each of four gambling-related charges, said Assistant U.S. Attorney Paul A. Sarmousakis.
Government prosecutors filed a 73-page affidavit from an Internal Revenue Service agent to buttress their case. The affidavit outlines information obtained through court-authorized wiretaps of three phone numbers allegedly used by Mastronardo in a betting house in Hatboro.
Mastronardo's attorney, James D. Crawford, said that at Tuesday's hearing his client would not "dispute that he made and booked bets and that the government can prove it."
The attorney said that Mastronardo "is somebody who likes the action of betting and made money doing it."
"But do we want to fill up jails with people engaged in gambling?" Crawford asked. "Everybody involved was a willing participant."
Crawford said that the sentence Mastronardo received in 1987 was especially severe because the gambling conviction was tied to the money- laundering verdict that later was overturned.
"If the government prosecuted nothing but gambling . . . it is extremely unlikely that he would have gotten 18 months plus probation," Crawford said. ''In a sense he has paid a high price."
According to the affidavit, Mastronardo can be heard on audio tapes giving gambling odds, taking bets, discussing deadbeats and talking deals with bookies from New York to Florida.
A total of 1,409 telephone calls were logged on the three lines. All but 22 were "pertinent to the bookmaking operation," according to IRS Agent Frank E. Gormley Jr. He said $950,000 in wagers was taken during the 12 days of wiretaps, from Jan. 25 to Feb. 5.
"You didn't know I took big money?" Mastronardo asks a client in one call. "Do you think the newspapers lied?"
"I run the show," he says in a second call. "I did the time."
"I'm here every night," Mastronardo says in a third call with a bettor. ''That's what I do for a living."
And what a living.
Investigators say Mastronardo schmoozed with his socially elite clients, steered clear of organized mobsters and never strong-armed his deadbeat customers. If they stiffed him, Mastronardo wrote off the debt and simply refused further bets.
Mastronardo cultivated top-dollar bettors, playing golf with them - sometimes for money. He even sent them Christmas cards (that contained his office hours).
"He's very mannerly, very polite," said one investigator who has followed him for years. "He handles himself in the fashion you'd expect of someone on Wall Street."
It paid off.
The array of clients who testified at his 1987 trial read like a society column - businessmen, brokers, blue bloods and more.
The men who pursued Mastronardo paid him grudging admiration as a man whose high-tech innovations taxed police to the max.
He used computers, call forwarding, 800 numbers and fax machines. He coded telephone numbers in his records, changed the numbers often and used cellular phones to avoid taps.
"He was way ahead of his time," said former Philadelphia Police Inspector Frank Wallace, a supervisor in the department's Organized Crime Unit when Mastronardo's operation was wiretapped in 1982 and 1983.
"He was sophisticated. . . . A lot of people start out to be bookmakers, but not many are as successful as him."
Cpl. Robert Hillgen, who twice set up wiretap surveillance on Mastronardo, praised his cunning.
"He was the most intelligent man I ever worked on," Hillgen said. "It was like an enormous chess game playing Joe. He knew I was always after him and I think Joe drew excitement from outsmarting police."
Friends and former associates acknowledge that Mastronardo is heavy into gambling.
"It's very sad," said one longtime friend. "He is kind, very gentle, honest as any man, someone very loyal to friends . . . who has a very serious gambling addiction.
"Joe is not a traditional bookmaker," the friend said. "A bookmaker takes an equal number of bets on each side of the game. Mastronardo is a gambler. He will take whatever action he can get. He will take wagers without balancing the books."
The investigators who chased Mastronardo think differently.
"He had such volume he didn't have to edge off" to balance the books, countered one investigator familiar with his case. "And he is addicted to the business, not to gambling."
Joseph Vito Mastronardo Jr. grew up in West Oak Lane, in a single-family house on the shady 8200 block of Cedarbrook Avenue.
His parents, Lucy and Joseph V. Mastronardo Sr., lived just two blocks from the home of Frank Rizzo and family.
This fact proved significant when Rizzo's daughter, Joanna, dropped by the Mastronardo house and met young Joe in 1971. Seven years later they married.
Joe Jr. has a younger brother, John, who was an all-America receiver at Villanova and a Philadelphia Eagles tryout.
Eventually, John became a co-defendant with his brother and father in Mastronardo's 1987 federal bookmaking trial. All three were found guilty. John was sentenced to a three-month term and a $25,000 fine. The father was sentenced to one year in jail and a fine of $125,000.
"Joe started school a year early so he was always a year ahead of where he was supposed to be," his brother said in an interview last week from Florida.
"He's a driven guy. If he wasn't so driven I don't think he'd find himself in the situation he's in."
As a youngster, Joseph Jr. tended greens and caddied at the Squires Golf Club in Ambler.
At La Salle University, he majored in pre-law and played on the golf team. The preseason guide for La Salle's 1969 golf team notes that he was "the hardest hitter on the team and the maturation of his . . . play will make Joe a sure point winner."
Mastronardo got into bookmaking, according to investigators, after college, working first for his father, "who had a lot of connections."
But his brother says it was the influence of the country clubs that pulled Joe into betting, not their father.
"He used to hang around country clubs, and as a locker-room or shoeshine boy one of the responsibilities is to call in the bets for members," John Mastronardo said.
Joe Mastronardo was arrested, but acquitted, on bookmaking charges in 1975. He was arrested again in 1978. That case was dropped after a judge ordered evidence suppressed.
The same year, Mastronardo became engaged to Joanna Rizzo.
Today, friends of Frank Rizzo's are reluctant to talk about Mastronardo. Rizzo himself always refused to discuss his son-in-law publicly or privately.
When Mastronardo was arrested in May 1978 - a month after he had presented Joanna a diamond on her birthday - police did not know whom they had busted until after he was hauled in, Hillgen said. But there was never any interference from City Hall in the investigation, police said.
Investigators agree that Frank Rizzo had nothing to do with Mastronardo's betting operations. But they also agree the Rizzo connection created complications for their betting investigation.
In 1982, Mastronardo's phones again were tapped by police seeking to close down his betting operation. Concern about leaks from the department to the Rizzo family was so intense that the wiretaps were run from a secret room in the Organized Crime Unit quarters at Third and Race Streets.
Mastronardo's operation was raided in 1983, the very night Rizzo was to debate Wilson Goode on television in his bid to regain the mayor's job.
The Rizzo people cried foul, charging politics in the timing of the crackdown. Police maintain the decision was prompted by a judge who wanted the probe done before she went on vacation.
When Rizzo died last month, Mastronardo was at the funeral with the rest of the family, at Joanna's side, behind his son, Joey. In the photographs taken outside the church after the funeral, Mastronardo can be seen somberly following the casket.
He is crying.
Salvatore Gambone remembers the night he and his wife went out to Bookbinders with Joe Mastronardo and his wife.
"He paid for everything," said Gambone, who testified in 1987 that he once bet $25,000 on a single game with Mastronardo. "He was always a perfect gentleman."
And for all the money and influence he was said to have, Joe Mastronardo wasn't flashy.
"He didn't hang at nightclubs drinking downtown . . . with wise guys," former police inspector Wallace said.
The Mastronardo house in Huntingdon Valley, which was placed solely in Joanna's name in March, is hardly palatial - three acres, near a golf course, seven rooms, $3,309 in taxes.
It's a quiet street, and he's a quiet resident who walks the dog every night, keeps to himself and leaves others to themselves.
"He is a very fine and wonderful person," said one neighbor, who spoke only if not identified.
"The guy's not John Dillinger, not a dangerous guy, but he's a bookmaker. A big one. A good one."
No dispute there, said Mastronardo's brother.
"He's a gambler," John Mastronardo said. "His friends are gamblers. He never put a gun to anyone's head. He didn't take food out of anybody's children's mouths.
"If Joe goes to jail," John Mastronardo said, "the world will not be any better place . . .
"And there will still be gambling."