Don't worry, it's not like in the CSI series, where they find a hair strand and put it in their data base and find the criminal. You actually have to have that person already in your database so you could compare the fingerprints and dna. As far as I know, Sangwoo has no crimes up in database so they have nothing to compare the dna with. By the way, dna does not stay on things forever and it's pretty complicated and super expencive prosedure to get a sample of it from a food. Gum would kind of work but like I said, it's not like those stupid and idiotic CSI series where they are able to tell the the car which the victim was driving before death just by the print of the car's tires :D Most people are not like Sherlock Holmes either... trust me, real police work is not that exciting and the financial funding is quite low or nonexcisting to make these kind of expencive reaserach... It would be cool and really wonderful if the policework was like in movies but in reality there are so many unsolved cases due to low funding and lack of money
Nice catch, didn't even think of matching up tooth impressions.
Sangwoo you dumbass! you left the apple with your DNA on it!!! if you're going to hide a body do it right smh （￣へ￣）