I appreciate the spoiler tag on the 70 year old movie.

Not a lawyer, but I believe that if the court found out, it would probably lead to a mistrial.

Would love to see Legal Eagle cover that movie.

First off, it's been a decade or two since I saw the movie. That said, there's a bunch of questionable content there, but I would argue that noticing and pointing out the glasses indentations isn't one of them. People do notice and put emphasis on different things.

For example, in this old reddit thread, a man is a dead ringer for a robbery suspect, down to the clothes he was wearing. But one person on the jury was a professional seamstress, and pointed out that the sewn-in pleats on the shirt the man was wearing vs the pleats on the suspect's shirt were completely different. No one - not the prosecutor, the defendant's lawyers, not the judge, not the defendant himself - noticed the seams or thought they were significant. But that seamstress did.

In both cases, this wasn't something they sought out to bring in from the outside, it was knowledge that they already had that they applied to the case. And I would argue that that's part of the responsibility of a jury. If I was on a jury listening to an audio recording that included ... I dunno, a plane engine or a train engine, and there was a plane mechanic or a train enthusiast on the jury, I would hope they'd point out whether the recording with the engine did or didn't match the suspect's. Because I certainly couldn't tell engine sounds apart, but someone who's around them all day could, and that's certainly relevant information.

Small nitpick, but they were jurors, not jurists. There is a difference.

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!

I don't believe it was legal, no. However, that does not necessarily work against the film as jurors frequently ignore the court's instructions and do their own thing (including doing their own independent research and discussing/introducing that to their other jurors). You hear about it when they get caught, but I have to assume that in many cases they do not. I guess it adds a further interesting dynamic to the film. Was it right for the juror to disobey the court's instructions in pursuit of his own belief that the accused was innocent? Is strict adherence to the laws our society's function under more important than adherence to our own moral code?

There was a reality TV show in Australia last year where a jury of 12 people sat through a full re-enactment of a real manslaughter trial that occurred in Australia and then had to reach their own verdict. The real life verdict was only revealed after they'd submitted theirs. It was pretty interesting how difficult it was for certain people to follow the court's instructions, put aside their own beliefs and preconceptions and focus on the facts of the case. I get the feeling that if someone these people had been called up for jury duty in real life, they 100% would have pulled a Juror 8 and just done whatever was necessary to reach the "right" verdict.

I just want to get out of here and get to a baseball game. Can we hurry this thing up.

spoilers

You know, i think if you haven't seen a 70 year old movie, that's on you.

Theoretically whatever the jury decides goes, and there isn't really a way to make them not consider information they learned inside or outside of the courtroom. They can be instructed not to weigh their decision on things they see and here, but some bells ring too loud to be unrung.

As far as specific legality goes? If no one's in the forest, does the falling tree make noise?

I think it's fine to come up with alternative theories if that supports reasonable doubt. If you can think of other ways the evidence could exist, there is doubt that it happened the way the prosecutor said.

Bringing in a knife from the outside does seem a bit dodgy though. Firstly just getting it into the court would be impossible today.