Huge spoilers ahead!
The jury, in particular the main protagonist, seemed to wade into illegal territory more than once. But being a complete layman who’s never been on a jury, I don’t know for sure.
Doing one’s own research and bringing one’s own “evidence” into the jury room, and not presenting it to the prosecution or defence, seems like a no no. The knife the protagonist finds in a store and brings in to show his fellow jurists that the prosecutor was wrong about its uniqueness; this feels like mistrial levels of inappropriate. Making judgements about credibility based on whether or not someone was wearing their glasses in court by noticing their nose has the telltale markings of a glasses wearer, something not pointed to by the defence as worthy of note, likewise seems off limits.
Is it not the case that the jury has to work only with information and evidence presented during the trial? And in fact can be told to ignore certain evidence from the trial if the judge deems it stricken from the record? Is it expected or acceptable for jurists to come up with their own alternate scenarios and narratives that fit the evidence or are they bound only to consider the theories presented by the defence and the prosecution?
Perhaps in the '50s this was all above board but the law changed since then. Or maybe my movie-based understanding of juries is a Frankenstein mishmash of true and bullshit. Probably that.
Great film deserving of its place atop “best films ever” lists, and I even liked the '90s remake!


Unrelated mini-rant. I had an assignment to write a couple of pages about the logical fallacies evident in the movie shown by one of the jurors, but not number eight. Number eight did have a lot of confirmation bias. I asked if I could write that, and my instructor just went “Sure, go ahead. I’ll be able to give you a zero in the first paragraph and it’ll save me a ton of time making!” This was in a unit called “open-mindedness.” Ty, you’re an ass-hat. Also, a shit teacher!