Dude. Because you usually don't suspect the teenager son to be the murderer.
You are right , but the risk of being caught wasn't zero !
There are cases with teenage murderer , one I can remember is Menendez brothers who killed their parents . Allegedly because of sexual and emotional abuse during their childhood .if Sangwoo had cleaned the blood spatter, he could report his mother is missing and this wouldn't have had any risk . Or if he abandoned her body somewhere else like his father's corpse the risk of being a suspect would have been low . I think this doesn't look like Sangwoo.
why Sangwoo didn't clean blood spatter ? He always clean after his mess!
What make him confidant he woulden't be a suspect ?
I realy want more details ┗( T﹏T )┛