[TapamN]

Weird coincidence, but I had to look through some old files backed up from the computer I was using 15+ years ago, and noticed it had C:\DeusEx sitting right there, with the SDK files in it. I found the function that handles damage in it.

https://pastebin.com/bwjaiDj7

It looks like I misremembered/misinterpreted some stuff. It looks like the top of the head behaves like the sides of the head, extending upward, forming a + shape.

Judging by how the arm/leg damage works, it the collision hit zones rotate with the enemy. Offset appears to be were the collision point is releative to the character's rotation, since it's also used to determine front/back and left/right collision. So for a hit to count as a headshot, it has to hit a cardinal octant of the collision cylinder.

Edit:

Updated diagram: https://imgur.com/a/Mec7HGm