I think a film like T-MEN may have gotten to the "procedural" idea first, but it's more of an undercover story. THE NAKED CITY is kind of anomalous in Dassin's output, since he was usually more focused on some form of the criminal type at the center of his story, but here (as is also the case with the upcoming THIEVES' HIGHWAY) we see some neo-realist influence in how he handles his visuals.
Here's what our late great Blackboard stalwart Bill MacVicar (bmacv) had to say about NAKED CITY:
An unrealized project of Alfred Hitchcock's was to make a movie about 24 hours in the life of a great city, probably New York. Producer Mark Hellinger enlisted director Jules Dassin to attempt a similar stunt. The result was The Naked City, a slice-of-life police procedural that served as template for the popular television series a decade later. And while the movie is nowhere near the ground-breaking cinematic enterprise that Hellinger promises in his introduction and ceaseless voice-over narration, it's not negligible. With its huge cast (many of them recognizable, even in mute or walk-on roles) and pioneering location shooting on the sidewalks of New York during the sweltering summer of 1947, it nonetheless continues to satisfy. Its documentary aspect outlives its suspense plot.
It opens with two men chloroforming and then drowning a high-profile model in her city apartment (shades of I Wake Up Screaming and Laura). When her cleaning lady finds her next morning, it falls to Detective Lieutenant Barry Fitzgerald, with his heather-honey lilt, and his principal investigator, Don Taylor, to fit the pieces together. Soon into their web flits Howard Duff, an affable, educated loafer with no visible means of support who lies even when the truth would do him no harm. It seems he was on cozy terms with the deceased, even though he's engaged to one of her co-workers (Dorothy Hart). But although Duff's a poor excuse for a human being, nothing seems to stick to him, either. So the police slog on through the broiling day and soupy night, knocking on doors and flashing pictures of the dead girl. Their sleuthing takes them, and us, up and down the hierarchy of the city's eight million souls, from society dames and society doctors to street vendors and street crazies.
While the plot never rises out of the routine, these urban excursions give the movie its raffish texture--and remain one of its chief pleasures. This was New York in the dawn of its post-war effloresence, a city where it was still common practice to live comfortably on modest--average--wages. The gap between East Side apartments and Lower East Side walkups, with the bathtub in the kitchen, doesn't yet seem impossible to cross. And its inhabitants burst on camera with a welter of accents and attitudes. Hellinger and Dassin must have enlisted the services of every character-actor and bit-player in the Tri-State area, and film buffs will have a trivia tournament in trying to pick them out.
The film ends with a chase over hot pavements and a stand-off high up on one of the bridges spanning the East River. It's a great set-piece, of the sort that action movies are all but required to include, but the movie's strength proves more subtle--it lies in its collection of sharply drawn vignettes (some of them, to be sure, little more than sentimental schtik). The Naked City is a rarity--a major production where the day players outshine the stars.