Jean Louis Trintignant did not receive an Oscar nomination, despite winning Cannes, for portraying the examining magistrate Christos Sartzetakis.
Jean Louis Trintignant could easily be argued as supporting in the film, and I would not argue that point long considering her only has a brief appearance for about the first third of the film where he is very awkwardly introduced to the entourage of the politician. I'll argue for his placement though simply for the second half where the investigation takes place as it fairly closely stays with the magistrate as he attempts to decipher the facts. Trintignant's role is unique in the film in that he is in no way politically charged unlike the doomed politician and his supporters who are constantly charged with their outrage and philosophy, or the men setting up the assassination who are consistently charged by their passionate hate for what the politician stands for. The magistrate on the other hand has different concerns. This shown early on in the awkward meeting which Trintignant plays as well as he no way expresses support to their anguish, nor does he suggest any malice towards. Trintignant actually does well by showing that the magistrate hardly feels anything towards them.
The magistrate does not pop back in until after the assassination and he is called upon to investigate what the authorities want at first to be deemed an accident. I must say I cared very little for Trintignant's turn as basically the quite observant lead in The Conformist just one year later, although here Trintigant is far more effective in this understated sort of role. Trintignant manages to make himself compelling by conveying the magistrate as someone taking in the information to decipher what exactly happened. Trintignant does well with a strong incisive glare towards everyone who speaks as it is clear the magistrate is not there to take sides but find truths. Trintignant is technically the one character who has an arc in the film although not in the usual manner still. This is not a personal emotional arc that Trintignant presents rather a strictly professional one. Trintignant never shows the magistrate lose his reserve exactly. He keeps himself consistent as a professional above else as the magistrate wants to find out what happened because it is the right thing to do as well as his job, nothing else is needed for him.
The magistrate even begins taking it as an accident, and adjusting statements that claim it otherwise since there is on hard evidence of the assassination at first. Trintignant does well to keep a certain reserve as he expresses both the magistrate particular method of deriving information as well as his personal distance from the case. Trintignant carefully portrays the actual arc of the magistrate because it is technically a somewhat detached transition. What Trintignant does well is create the calculation within the magistrate and is convincing in the gradual way he realizes the magistrate figuring out what happened. When the magistrate starts allowing to be called a murder Trintignant earns it through his subtle though quite honest reactions to every bit of information that is known. Of course it is not merely about deciphering information but also about deriving it himself through his interrogation of some of the culprits. Trintignant is very effective in these scenes as he plays the magistrate always quietly in control of the situation watching for any misstep, and delivers his more incisive remarks with the utmost precision.
Although Tritignant never wholly loses his reserve in the parts he does have a few great moments where he shows what the magistrate is feeling. Of course again Trintignant does not play these again as a political thing, but rather just wholly involving what is right. In fact that is the way the character must be since it is alluded to that the magistrate's personal political views technically skew closer to the villains, and that is what leaves him protected from scrutiny by the officials. One of my favorite moments in his performance is when he gets the brains behind the operation to say the exact same line that all the conspirators say when describing part of the assassination. His slight smile is just perfect as the magistrate does take some satisfaction in knowing he's gotten the one responsible. Trintignant technically had quite a challenge with this part because the magistrate is technically on a whole different wavelength from every other character in the film. Trintignant uses that to his advantage as his work stands out through his intriguing depiction of a man whose sole motivation is justice.