Welcome to my 100% Achievement Guide for Ghost Files (MOAC)!
(Note, When there is no commentary in the video, i had to mute for copyright reasons)
This is again, technically unmissable as we need to do it to advance the story.
This is easier than the forensic one from earlier on.
In chapter 4, you get murphys Fingerprint from a gun, open up your forensic table by pressing
on the D-pad.
to get both fingerprints on the table, then use the green bottle to spray them both.
You will have a slight minigame then where you have to find the irregularities in the fingerprints which isn't too hard and doesn't take long.
But of course, if you want to see where they are without a fuss, go to 1:18:20 in the video below.
Hope This Helps!