Responses

It wasn't shown here but in the novel the female officer who came told yiyeon that creepy stalker had bribed the cops and gotten higher ups involved. Everybody at the police station knows the alibi's are false and that he's stalking her but they're deliberately not doing anything. So setting up cameras won't do shit since no one will believe her despite the proof.
She knows he stares at her through the same spot why didn't she set up a camera? Oh but then he would stay somewhere out of view. And that's when she snipes his stinky stalking ass...then those stupid cops can't say anything because what there's a camera at her house you would've seen her