Which of the following methods is used for demonstrating old washed up blood-stains -
Luminol (3-aminophthalhydrazide) spray is most common blood reagent used for visualizing/demonstrating weak/ faint blood stains i.e old washed up or cleaned up stains and blood stains in areas difficult to see such as outdoor vegetations etc.
Infrared photography
Luminol spray
Ultraviolet light
Magnifying lens