Chris Richmond’s review published on Letterboxd :
In the rundown, poor town of Sparta, Mississippi, it is very hot, and the people drink Coca-Cola.
Much like Do the Right Thing, the "heat" in this film is both a literally frustrating and nigh-impossible-to-remove element that permeates the atmosphere and a likewise constant boiling over of emotions running high. Emotions stemming from all the way back to the Civil War for some, and even farther behind that for others.
This film is not only about racial tensions. It is smartly also about the North's decimation and subsequent condescension of the South. It is also about the difference between having money in your pocket and not. It is, most importantly perhaps, about the distribution of power, and how that intersects with things like money and race.
The racial prejudice portion of the film is far from preachy, but it's not exactly subtle either. The other elements I just mentioned are. They're found not only in the assumptions made based on who has a certain amount of bills in their wallet, their purse, or their bank account, but additionally within the contrasting perception of the widowed Chicago native and the similarly confident and looking down his nose of Officer Tibbs himself.
Tibbs is, of course, played marvelously by Sidney Poitier, with impressive poise and a steely glare that manages to be convincingly intimidating in the face of odds stacked against. Arguably more impressive is Rod Steiger in his performance as the gum-mashing, irritable but secretly contemplative Chief Gillepsie. The entire cast delivers strong performances, but these two stand head and shoulders above the rest.
Director Norman Jewison approaches the murder-mystery from a narrative arc that's more concerned with the goings-on of the investigation and its participants than the actual resolution, and that's reflected in the film itself. Clues and progress in the case have relatively little weight or impact, but that's certainly made up for by the alternate focus.
Part of the reason he gets away with it is the fast-paced, inventive filmmaking that features a bevy of shots and interesting editing, carefully balancing wide and medium framing with occasional close-ups that are made more gripping by their rarity.
The camerawork and composition can feel mildly forced, and the lighting is hit-or-miss, especially in regards to proper exposure for Poitier, but mostly In the Heat of the Night is a visual success.
Storywise, it would have been nice to have seen a few interesting characters like Endicott and Mrs. Colbert get a little more screen time, but the fact that they're interesting enough to elicit this dissatisfaction is testament to the strength of their foundation.
While it isn't quite revolutionary or awe-inspiring on any singular front (save, perhaps, the marvelous acting), In the Heat of the Night accomplishes its mission as an examination of social structure, the power of money, and the danger of assumption while masquerading as a procedural drama.