A friend of Johnny Sack's from Brooklyn who became his consigliere once Johnny took over as boss of the family.
Petrile goes to the morgue with Phil after the body of Billy Leotardo is released and offers to identify the body, to save Phil the hardship. The scene with Jimmy and Phil mimics the scene in The Godfather when Vito Corleone and Michael Corleone go to the morgue to see the body of Sonny Corleone and have the mortician Buonasera to reconstruct the bullet-riddled Sonny. But Phil turns the offer down.
When Billy Leotardo is shot dead by Tony Blundetto, Jimmy is the one that calls Tony Soprano and tells him.
Later, he sits in on one of the discussions with Tony and Phil over the Tony Blundetto situation and tells Phil that he gets emotional when he drinks wine. He is also the one that notifies Tony Soprano by telephone from a deli in Little Italy, Manhattan in code that John Sacrimoni took over the reign of the family from Carmine Lupertazzi Jr. in a bloodless coup.
However, it is revealed in "All Due Respect" that Petrille had been a cooperating witness with the FBI and gave up information on transport truck hijacking and drug dealing going back to Sacrimoni's criminal activities in 1981, which was instrumental in Johnny's arrest by the Assistant District Attorney in Brooklyn.
Tony, who is much younger than the senior Petrille (Vella is born January 11, 1947) remembers that Petrille is a "sweet, old guy..." and is shocked that he is a cooperating witness against John Sacrimoni.