Flashlights are a must for any investigator. In most investigations, this will be the only light source you will have. When using the flashlight, each investigator shall have a red filter fitted to the lens of his/her flashlight. Red light preserves your night vision. Red lights are used in photography dark rooms, military bunkers, submarines, and anywhere you might find yourself working in the dark. It gives you light to see by, while at the same time keeping your eyes adjusted for the dark.
Cap lights are not forbidden, but are discouraged and should only be used during a break since they typically tend to “blind” people at eye level.