But the former wiseguy turned government witness stuck to his story: Borgesi, his former captain, was a ruthless killer who oversaw an extortion and sports betting empire from behind bars. Ligambi was the man steering the Mafia's ship.
"You're really nitpicking at nothing here," Monacello responded under cross-examination by Ligambi's lawyer, Edwin Jacobs Jr. "You're making mountains out of molehills."
For much of the last decade, Monacello testified, he helped run Borgesi's rackets in Delaware County while the mob captain served out a prison term on unrelated charges. He also collected "Christmas taxes" for Ligambi, gathering cash each December from South Philadelphia bookmakers looking to operate without mob interference.
Throughout the day Monday, Jacobs sought to characterize Monacello as a lying opportunist, prepared to fabricate salacious stories about his former friends in an attempt to save himself from a lengthy prison term.
For his part, Monacello proved willing - at times even eager - to air the Philadelphia Mafia's dirty laundry during his time on the stand.
To hear him tell it, mob life, with its family rivalries, petty jealousies, and repeated bouts of one-upmanship, more closely resembled episodes of Days of Our Lives than anything dreamed up in The Godfather.
According to Monacello:
Anthony Borgesi, George's kid brother, resented that he had been passed over to run the family business while his brother was in prison and sought to undermine Monacello at every turn.
George Borgesi's wife, Alyson, henpecked her husband's soldiers, accepted cash payments stuffed into her glove box, and fiercely guarded her family's interests - earning her the nickname "Alyson Corleone."
Angelo Lutz, a Borgesi family friend, once wrote Ligambi from prison to accuse Monacello and Borgesi of stealing money.
Monacello was not immune, either. He told jurors Monday that after a former associate tattled to Monacello's wife that her husband had been sleeping around, he wrote an anonymous letter to the Catholic school where the man worked to inform administrators of his criminal past.
"Don't be fooled by this little family facade they have going on here," Monacello said. "They all hate each other."
In fact, it was another such feud, Monacello said, that led to his decision to switch sides and testify against his former associates.
In 2008, he said, he hired a man to attack a rival mob captain who he believed was moving in on his business. Borgesi found out, became upset, and began plotting to murder his former friend, Monacello said.
"The only reason I'm sitting here and not over there with them," he said, gesturing toward Ligambi and Borgesi at the defense table, "is because they were going to kill me."
Such stories became the backbone of Ligambi's and Borgesi's first trial last year. But Monacello's brash and at times cocky testimony was contradicted by several other witnesses, leading the jury to deadlock on several of the most important counts against the two men.
This time, Monacello appeared to take pains to tone down his style - though that didn't stop Ligambi's lawyer from needling him on discrepancies in his story.
As Monacello recounted several white lies he told the alleged mob boss over the years, Jacobs questioned why - if Ligambi was the violent thug that Monacello said he was - the former bookmaker felt comfortable lying to his boss.
"This isn't corporate America," Monacello shot back. "Remember, we're criminals."