Why would the blood dry out faster on the face than on the presumably hot roof? What is on the shirt, and on the roof, looks more moist than the marks on the face.

Okay, maybe the corpse was moved right before the photo was taken so it was over the blood smears on the roof and the only part exposed to something like wind was what is on the face, and that slowed the drying of the blood on the roof - even if the roof was presumably hotter - and on the shirt, but I'd still like to know how long the corpse was on the roof before the photo was taken, and if it was moved before the photo was taken.