I've never seen a movie like this, very special. Wow.
Anyway....
Was the young man a mute or isn't it like that? I understand the idea of the movie, he doesn't say a word to the lady but they bond very well. But at the police station, he could have said he didn't kill the man and not have kept quiet all the time. I guess there's no real explanation for it. The maker of the movie probably just wanted it like this.
I was shocked at the scene where his golfball hits the young lady in the car, and i can't be sure...but it didn't look good, i'd think she died there, damn :(. His 'moves' and 'training' in the jailcell, was all meant for later use, to be able to stay out of sight and 'creep' even better, right?
As for the scenes near the ending of the movie where he basically 'visits' all those homes and scaring people in the process....why?
It's been awhile since i've seen the movie, But i'll try to answer you as best as i can. I don't think that he was a mute, it was more like trying to be invisible.. undetected. This is why he teaches himself to be invisible. I think he talked when he was being interviewed by the police, they just didn't show it. The officer came out and said that he knew where the body was, etc. I think the reason he goes into peoples houses and does the random things that he does is sort of a way to leave his mark. A random thing is different, but you don't know why, and it's never really a major thing so you don't remember it for very long. But later, he has the ability to go into their homes and change something, making it more noticed than before.
No other offense has ever been visited with such severe penalties as seeking to help the oppressed.
I've just watched this film for the fourth or fifth time, and it has left me amazed by its beauty every time. So wonderful and special indeed. Concerning your first question, I don't think the young guy was a mute. Being silent was more like a way of living: words can only make things less real than when they are experienced only. The contrast between reality and a world of fantasy was what the movie was about, after all. It would have made things easier at the police station, when he wouldn't have remained silent. But wouldn't that have been a shame? I think keeping silent suited his character way better.
In my opinion, in the jail he's practicing to become invisible. In the fourth and last jail-scene, he's actually become a ghost. Afterwards, the guards take him into a long tunnel, with white light in the end. I believe that is when he dies and when he has really made it into invisibility - the state he always wanted to achieve, also by living in other people's houses. I think in this regard, the most beautiful shot is the one where he and the girl are standing on the balance together, weighing nothing. A beautiful reference to his invisibility, I would say.
I think however that there's no one right story to tell about this movie. Everything could be possible, if you want to believe it - that's the power of the storytelling.
I have a question for you too. What is your idea about why the girl keeps standing in front of him when he wants to hit the golfball? I thought of two options. Either she wants to see if he can be trusted, since she is used to being with a unreliable husband, or she is in the middle of the process of transforming from subjugated woman into a woman who is able to protect herself. That point is reflected in later shots as well, for example the one in which her husband hits her and she hits back. I would like to hear your opinion on this. Thanks!