Ok, so who did it?

On top of that later... the son suggests that maybe the "killer" would have dragged her up to the roof for all to see, so somebody could come HELP her (which gives insight into what HE was thinking when he put her up there on the roof).

His alternate explanation (to the "displaying the revenge for the whole village to see" theory) for a motive for bringing the girl to the roof further evidence that the old man's story was true.

Otherwise there's no reason for him to bring that up.

Yes, the son. And their letting the other odd chunky young dude with glasses take the fall.

How can a mentally ill kill someone?

The son killed her - you are wrong.

Nothing you say proves otherwise...

It aint like it used to be, but it'll do

The film intentionally omits some scenes in the beginning IN ORDER TO TRICK VIEWERS.

When the merchant reveals the whole truth, the shock is even greater. The mother's son is the killer. In the end, he even explains why he dragged the body up to the roof! I don't understand how some people refuse to understand that.

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The scene where we see him slouching away after the boulder was thrown at him was cut short because the son's memory blocked out the murder, either from self-preservation, mental illness or drunkenness. He did commit the murder, the junk dealer had no motive to lie. If it was him who murdered the girl then he wouldn't have brought it up in the first place.

THE SON KILLED THE GIRL. Any reason to disprove this is rubbish, and whoever tries to argue is a retard themselves.
The innocent man put in jail was also retarded (he claimed they were lovers, which isn't true because the girl, before her death, yells out how much she hates men. he was obsessed with pretty girls, and so was DO-JOON) MEMORIES OF MURDER also had a situation where a retarded man was being blamed for something he did not do (which is obviously an issue in Korea between detectives and suspects)
But in this case, it WAS the retard.

"There's no break in the film to indicate that something happened between the boulder and his leaving" WTF does that mean? There is no break because there was an entire proceeding sequence where he throws the rock back because the girl called him a retard.
ONCE THE ROCK HIT HER, SHE DID NOT INSTANTLY DIE. LATER, HE REMINISCES AROUND THE DINNER TABLE THAT SHE WAS BLEEDING AND NEEDED TO GO TO THE HOSPITAL. (SOMETHING ONLY THE MURDERER WOULD KNOW) HE DOES NOT FULLY REMEMBER, BUT SAYS THAT IF IT WAS HIM, HE WOULD HAVE PUT THE GIRL UP ON THOSE STAIRS SO PEOPLE CAN HELP HER QUICKLY. SO OBVIOUSLY, HE DIDN'T INTENTIONALLY KILL THE GIRL. HE DID NOT KNOW HOW TO REACT AND LEFT HER TO BLEED OUT.

it's EXTREMELY sad that you enjoyed the movie as much as the next person, but can't even understand the whole point of it..

Because he had had sex with her in the past?

I don't think the director wanted it to be clear as to who actually killed the girl. That's why some people think that the son did it, and some think it was the junk man. There is ANOTHER possibility as well, if you remember the golf ball and the son's friend who made a lot of money out of the whole thing (he knew the girl, he knew about the golf balls, and he didn't turn up at the pub that night, etc). So there are three suspects and everyone can decide for themselves who they prefer to see as the killer.

while I agree wutg you philebus, theres just something bout this film i wanna love so im not listening so there lol. I will submit that the extra half hour was too much they should have wrapped the story up after mother killed the old man-it would have had a lot more impact then in my view-son staying in jail rightly, but for the wrong reasons and mother living with the big secret that not only that she knows son is the real murderer (but because of her earlier actions having to keep up the facade that she thinks he is innocent), but also she is a murderer too- actually I thought she was going to make another insectiside drink again and commit suicide successfully.

it was Sue Ellen