A Wood's lamp has been recommended as a means to identify semen stains during rape evaluation.


A Wood's lamp emits ultraviolet light at 360 nm. It is shined on a surface in a darkened room.


Semen fluoresces at a wavelength of 450-500 nm. It may not fluoresce at the wavelength emitted by a Wood's lamp.


Some of the material that may fluoresce under a Wood's lamp:

(1) urine, blood or other body fluids

(2) common medical lubricants and creams

(3) bacitracin or other antibiotic cream

(4) tonic water (associated with quinine)

(5) vitamins

(6) chlorophyll

(7) laundry detergent

(8) antifreeze

(9) Castille soap



(1) A Wood's lamp is not a good method to screen an area for semen.

(2) One cannot assume that something that fluoresces is semen. Additional testing is required to confirm the origin of material.


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