TESTIMONY in the federal racketeering retrial of reputed Philadelphia mob boss Joseph "Uncle Joe" Ligambi and his nephew George Borgesi, an alleged mob captain, had been somewhat dry until yesterday afternoon.

But that's when star witness Louis "Bent Finger Lou" Monacello, a former associate of Philadelphia's mob family, regaled jurors with past tales of blood and gore.

There was the time in the mid-1990s when Borgesi's brother, Anthony, was having a bachelor party at a South Philly restaurant. Another mob associate, Angelo Lutz, took care of the room setup, but with 20 to 30 guys, it was crowded, Monacello said.

Because of that, George Borgesi "bites a chunk of skin out of his [Lutz's] forehead and makes Angelo pick up the check," Monacello told jurors.

Another time, Borgesi brought Lutz to Monacello's home and in the basement, Borgesi "throws Angelo up against the wall" and yells, "Tell me about the checks you forged!" Monacello recalled. Borgesi then swiped a rod from a fake Christmas tree and "splits Angelo's head open," seriously wounding him.

Ligambi, 74, and Borgesi, 50, aren't facing any counts of homicide or assault. The indictment against them focuses on sports betting, loan-sharking, extortion and the operation of video-poker machines. The main charge they face is RICO (racketeering) conspiracy. The feds are looking to prove that Ligambi and Borgesi conspired with others to commit crimes.

Monacello, 47, a South Philly guy, befriended Borgesi when the two were teens. He eventually got into sports betting and became an associate of Borgesi's crew. They were close friends for 30 years until their arrest in 2011 under the current indictment, and Monacello then became a cooperating government witness.

Monacello said Borgesi had been promoted to captain, and Ligambi "told me on several occasions, 'I'm the boss of the mob.' "

Under questioning by Assistant U.S. Attorney John Han, Monacello focused mostly on Borgesi - how he used violence or the threat of violence to collect money or to get revenge on a rival.

"He was a feared guy," Monacello said of Borgesi.

Once, in the late 1990s, the two were riding in a car in South Philly and talking about someone who was recently killed when Borgesi turned the radio volume up high, flashed his hands twice and boasted: "Eleven murders. Me. I did it. I'm responsible. I'm a professional," Monacello said.

(Borgesi has never been convicted of murder.)

Monacello also admitted to participating in violence himself, saying it was under Borgesi's orders. Around 1998, Borgesi wanted revenge on a man who had gotten the better of him during a fight.

Monacello said he and others waited outside the man's South Philly house and surprised him when he was walking his dog. Wearing a ski mask and wielding a baseball bat, Monacello said he "swung all my might and split [the man's] head," injuring him.

Asked about his nickname, Monacello showed jurors his right hand with its bent index finger. The result of "a fight," he said.

Monacello resumes his testimony Monday.

On Twitter: @julieshawphilly