Stanley Allen Diamond was born in New York City, New York to Yiddish-speaking parents of Austrian-Polish-Jewish background, specifically from the area of Lviv, Galicia. He was fluent in Yiddish as well as German, which he was raised speaking, along with English. He was a sociopath and suffered from severe Autism and Aspergers Syndrome which caused him to have anger management problems.
Stanley was a close friend of Henry Hill, Thomas DeSimone, Anthony Stabile, Jimmy Burke and Joseph Allegro,. Stanley could never become a made member of the Vario Crew, like Henry Hill and Jimmy Burke because of his Jewish and Polish-Austrian heritage, but did not suffer the racial discrimination as did African-American crew member Parnell Edwards. Like Tommy DeSimone, Stanley was known to have a violent temper and was prone to outbursts which made him feared even by fellow mobsters. Stanley Diamond was one of Paul Vario's shooters who was known who sit around all day and brag to the other soldiers about his favorite mob executions he performed. He became friends with Tommy DeSimone, Henry Hill and Jimmy Burke. When hijacking transport trucks it was either Tommy DeSimone, Joseph Allegro or Stanley Diamond who would run up to the truck as it was stopped at a red light in the early morning hours and threaten the driver with a gun and put him in the mobster's car while other guys drove the truck to the stop.
In 1970, after Jimmy Burke told of plans to extort his thriving bookmaking business and Krugman threatened to go to the District Attorney, Frank Menna was the unfortunate employee who was beaten in the salon, in front of Krugman, by Stanley Diamond and Thomas DeSimone on orders by Jimmy Burke. Frank is lucky to have survived the beating due to DeSimone and Diamond's ruthlessness as sidewalk soldiers for Paul Vario. The beating was shown in the film to involve Martin Krugman and not Menna who is strangled by Jimmy Burke with telephone wire in the presence of Henry Hill.
Stanley murdered the freight supervisor of the legitimate truck warehouse near the James A. Farley Post OfficeNew York City's General Post Office, located at 421 Eighth Avenue, between 31st Street and 33rd Street in the New York City borough of Manhattan, across the street from Pennsylvania Station and Madison Garden at West 36th Street. The identity of the supervisor is not discovered, but he is described by Henry Hill as a "big chesty guy" who did not know who Jimmy Burke was and would not let Burke unload the hijacked cigarettes after his unloaders could not produce their union identification cards. After they could not come to an agreement Stanley Diamond and Henry Hill, while driving the truck several blocks from the warehouse down 9th Avenue, they noticed the back doors to the truck were open and cartons of Laredo cigarettes were spilling out onto the street. The truck was blocked off by a police cruiser and Diamond and Hill both bolted from the truck as it sat idling in the street. That very night Burke sent Diamond and Tommy DeSimone to Hoboken, New Jersey where the cargo supervisor lived as a bachelor to "straighten him out". They were just supposed to rough him up and tell him about Jimmy Burke. Instead Diamond and DeSimone got so mad at the cargo supervisor that they murdered him. The two were so angry that the supervisor wouldn't listen to Jimmy Burke at the warehouse, that he lived in Hoboken, New Jersey, and that they had drive twenty-five miles all night to New Jersey to talk to him, they got themselves so worked up, that Diamond and DeSimone couldn't stop themselves from killing him.
Stanley Diamond was ordered along with Henry Hill, Jimmy Burke, Thomas DeSimone and two carloads of Lucchese crime family side-walk soldiers to beat up the waiters and kitchen staff at Don Pepe's Vesuvio Restaurant located at 135-58 Lefferts Boulevard in South Ozone Park, Queens, just a few blocks south of the Lucchese crime family hijacking headquarters, Robert's LoungeH e assisted in beating the employees with an inch of lead pipe as the kitchen staff left the restaurant at 11 P.M. Some of the employees fled the scene and scrambled into the cars, so Stanley and others had to chase them all around the neighborhood late into the night. Stanley and the others had been ordered to beat the staff after a certain waiter spilled a drink all over Paul Vario's wife, Phyllis and then sloppily tried to blot up the spilled drink on the front of her dress.