A very well-made film, with great actors.
As a non-American myself, it's a little tricky for me to understand how well this justice system works. Don't get me wrong, but in my country it is not usual to resort to this type of trials, where the decision depends largely on the lawyers' ability to convince a group of jurors. Here, the decision depends more on the judge, or on a collective of judges. Resorting to a jury trial is provided for in Portuguese law, but must meet a tight set of prerequisites, which turns out to be a very unusual option.
So to understand this movie better I had to go read a little bit about how a real life jury trial works. And this is where my doubts about this film are greatest. Is it really a film that respects what really happens in the room where a jury deliberates what sentence to pass? Throughout the film, it is quite clear that the trial did not go well, mainly due to a largely ineffective defense and incapable of securing the interest of the accused (something difficult to admit, especially in a case of capital punishment). Could the jury have done anything about it other than pass sentence? I confess, I don't know. I leave this to the jurists, lawyers and people who can understand more about the subject.
The film is a bit like one of those plays that ends up being taken to the cinema: the action takes place overwhelmingly in the same environment, quite confined, and with a limited group of characters who interact with each other and dialogue. Dialogues are an essential part of the film and they are not always nice. It is noted that there is an increase in tensions, and if there are several jurors interested in dismissing the matter and leaving, this changes little by little, as the details are analyzed and doubts about the trial increase. It is a frankly well-written, well-directed film (Sidney Lumet's best) and with a strong and competent cast where Henry Fonda assumes an unequivocal role, giving us one of the best works of his career. Also, Lee J. Cobb deserves a round of applause for the way he interprets and acts, in a deeply caustic character. Every actor has the time and material he needs to do a good job, and they all did.
On a technical level, it is an extremely discreet film, largely due to the low budget it was limited to. However, it is one of those films that proves that it is not necessary to have infinite money to do an excellent job. The setting is very believable, but where Lumet shined was in his clever use of cinematography and shooting angles to amplify feelings of confinement or discomfort. Sometimes, the camera gets so close to the actors' faces that we can see how much the excessive heat and subject tension is getting on their nerves.