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.