This is one of those very rare films where the good guy is faced with difficult moral challenges - the kind that real people in the real world all face. Not only is he unsure who around him is clean or dirty, he's conflicted, as are we, about what the honorable course of action is.
Hollywood typically offers us only two choices in crime dramas. Scenario no.1 offers us a heroic good guy who, despite dealing with lazy, corrupt peers, overcomes all obsticles to defeat evil. (Dirty Harry). We can relax and enjoy the action precisely because the unwritten rule of this genre is that the hero will never face any moral quandries.
Scenario 2 ensures that our moral sensibilities won't be challenged by simply abandonning any notion of right and wrong. It invites us to cheer for the protagonist, without "judging" him or her. (Good Fellas, Bonnie & Clyde).
Night Falls on Manhattan tosses the rule book. The hero (Andy Garcia) is a good guy, trying to do the right thing - but under circumstances where there are no good options. The audience, like Garcia's character, is deeply conflicted over what he should do, what the outcome will be, and what outcome we want.
If there's a flaw, it's that the movie never quite gets off the ground emotionally. We are not deeply invested in the characters; the courtroom scenes never develop a sense of tension; even the shootouts lack drama.
That said, the combination of first-rate acting, engaging dialogue, and a refreshingly willingness to break the Hollywood rules earn this a 4.5.