Sudan Black
Introduction
One of the best processes
for developing latent prints on smooth or rough, nonporous surfaces
contaminated with greasy or sticky substances is Sudan Black.
It works best on glass, metal or plastic materials.
Sudan Black can be used
on waxy surfaces, such as candles or wax-paper milk cartons.
Sudan Black is a dye which stains the fatty components of sebaceous
secretions. Besides being sensitive to grease, oils and sticky
substances, Sudan Black will also enhance glue-developed latent
prints.
We have reports that this
process works very well on the inside of latex gloves. First,
the gloves must be treated with glue fumes, quite a bit heavier
than normal. Dip the gloves in the solution of Sudan Black for
about ten seconds and rinse in water. Continue to dip for ten
seconds and rinse until latent prints appear. Often, latent
prints will have better contrast after the surface dries.
Safety
As with any new chemical
process, read and understand the Material Safety Data Sheet
on all of the chemicals involved. Practice normal industrial
hygienic procedures of wearing lab coats, protective gloves,
and goggles, if there is any risk of splashing the solution
into the eyes. If the solution is going to be used for long
periods of time or on large surfaces, it is recommended that
it be done in a fume hood or with adequate ventilation. The
process of Sudan Black is easy, inexpensive and nontoxic. It
can be a bit messy so use some common sense regarding the area
you are working in to make the clean up easier.
Do not use this on porous
or absorbent items as the entire item will be stained a dark
color. This process may run inks, and interfere with blood and
body fluid examinations.
Mixing Instructions
Place 15 grams of Sudan
Black powder in a 2 liter glass beaker. Add 1 liter of denatured
ethanol and stir with a plastic stirring rod. Add 500 ml of
distilled water to the beaker and stir with the stirring rod.
A black working solution will result. Some of the Sudan Black
will not dissolve. Some will remain as particulate matter floating
in the solution or will appear as sediment. Pour the solution,
including any solid matter, into a clean glass bottle with a
tight-fitting screw top. Label the container appropriately.
The working solution has an indefinite shelf life.
Processing Instructions
Shake the container of
Sudan Black working solution and pour a sufficient amount into
a tray large enough to place the item of evidence. Soak the
item for 2 to 3 minutes. Rinse the article in cool, running
tap water. The solution in the tray can be poured back into
the bottle to be reused. Be certain that all undissolved dye
is also returned to the bottle.
For large items, pour the
solution over the surface, catching the run off in a tray for
reuse. Rinse with cool, running tap water.
Allow the item to dry at
room temperature. Applying heat is not recommended. Evaluate
the latent prints only after they have dried completely. Faintly
developed latent prints can sometimes be enhanced by reprocessing.
Latent prints developed
with Sudan Black should be photographed. While it is possible
to lift the prints with tape, the tape frequently does not lift
the print sufficiently. Therefore, it is strongly recommended
to photograph the latent prints before attempting to lift them.
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