The mugshot serves several purposes:
- It provides a visual representation of the overall health of the player (redundant with the health indicator and possibly the crosshair).
- It also gives directional indication for sources of damage, by "looking" in the direction of the damage source.
- It reveals the use of the god mode cheat.
- It also reacts to other events, such as grinning when picking up a new weapon or grimacing when holding fire for a while.
Of particular note is the ouch face bug which ZDoom fixed but which can be turned back on in the HUD options menu. A good reason to do so is if having a hint for the direction of the damage is found more important than having a hint for the intensity of said damage, since the standard ouch face always looks straight ahead.