Under what specific emergency circumstance is helmet removal by first responders strictly justified on an unconscious crash victim?

1. Only when the victim is unconscious AND has an obstructed airway or has stopped breathing, requiring immediate airway clearance, rescue breathing, or CPR/AED resuscitation
2. Whenever the rider complains of a headache
3. To check whether the helmet brand is authentic
4. Whenever it begins to rain lightly on the crash scene