The stuff youre talking about where forensic scientists spray stuff, they’re spraying Luminol to detect trace amounts of blood because it reacts with the iron in the blood traces and makes it luminescent enough for it to be photographed in a darkened room even without UV.
Body fluids can be detected just with a UV light yes.
Watch Gordon do it to a gross hotel https://www.youtube.com/watch?v=dQ4ZAZJphx4
The stuff youre talking about where forensic scientists spray stuff, they’re spraying Luminol to detect trace amounts of blood because it reacts with the iron in the blood traces and makes it luminescent enough for it to be photographed in a darkened room even without UV.