Can a uv light show up s***n/sperm stains??

Question

Can a uv light show up s***n/sperm stains??

Answer 1

The short answer to this one is yes but s***n stains are not exclusive in terms of body fluids that show up under UV light.

The principle by which this takes place is known as fluorescence which refers to the emission of radiation (esp. visible light) by a substance, typically during exposure to external radiation (lasers, X-rays, UV light). The substance absorbs light and re-emits the light in wavelengths longer (lower energy) than that of the illuminating source.

Ultimately if something does show up under UV light it is wise to perform another test to confirm the glowing stain as s***n as oppose to saliva, sweat or toothpaste. This can be achieved by using something like the Acid Phosphatase Test.

Finally there are cases where cotton fabric also exhibits florescence.  This can have the effect that the glow of the fabric under UV light masks any glow from s***n stains on it.  The effect of this can be reduced by altering the wavelength of the UV light, normally by adding more blue wavelengths too it.