Ultraviolet light can be used for close examination of the
article or area to reveal evidence that may not be visible to the
naked eye. UV light can also be used to sometimes reveal hidden
blood and fingerprints.
This portable UV light provides 4 watts of illumination that
can help to isolate suspected stains on large areas such as bedding,
furniture, or automobile interiors. However, a UV light CANNOT
conclusively identify a semen stain or any other kind of stain
because everything including toothpaste, coffee with cream and
sugar, urine, and even the brighteners found in many of today's
laundry detergents will all fluoresce when subjected to U.V. or
"black" light.