Continuity mistake: In the scene where Serpico is in his apartment speaking to his girlfriend explaining how hard it's been to be an honest cop, he is drinking what appears to be a full glass of white wine. In the following shot of the both of them, Serpico sets up two unused glasses, opens a bottle of wine and pours it into the two glasses. His original full glass of wine is nowhere to be seen.
Continuity mistake: Rizzo breaks up the rumble at the pizza joint; in the wide shots when he keeps the goons in check, there are several more unperturbed bottles in the shelves behind Manomozza than in close-ups. Some of the bottles that were in the side shelves in fact have inexplicably moved onto the center one. (00:11:25)Sammo