There's a shot of Manhattan, which is supposed to take place in 1973, however we can see a building from the World Financial Center which didn't exist in 1973 and the antenna on top of the north tower of the World Trade Center which wasn't there at the time. This is clearly a shot of the Manhattan skyline as it looked in the mid 1990s.
The audio played back in the courtroom is not the same as the conversation that took place earlier in the film. Notably, John Gotti used the phrase "physically sick" during the earlier conversation, but it does not appear when the tape is played back. Also when Gotti asks who "did the work?" Frankie says "Sammy," but on the tape, Frankie says "Fucking Sammy" which Gotti repeats.