Elliott Folds’s review published on Letterboxd:
Sidney Lumet was such a great director, and he saves Serpico from being more than a routine cop drama. There's a fascinating story here, but the script is a bit wandering. Characters come in and out of focus with no real explanation for their presence, but the one constant is Al Pacino's virtuoso performance. He's truly great, and it's easy to see why he was such an exciting up-and-comer in the early 70s.