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Advanced Techniques
for Developing
Latent Fingerprints
STEM
Ninhydrin:
Discovered for fingerprints in the
1970s by a university scientist
who was working on a process
that stains protein tissue sections.
After an accident he found that it
made his latent fingerprints
visible.
Major Advantage :
It can be applied to large
surfaces by using a spray
bottle.
Major Disadvantage
It is toxic and should be
used in well ventilated
areas.
How does it work?
Ninhydrin reacts with
the amino acids present
in the perspiration on
the print, turning the
print purple.
The reaction:
Iodine:
Up until the 1970s Iodine
fuming was one of the
classic/main methods to
visualize latent
fingerprints. This method
is now seldom used.
Iodine:
Iodine is one of the few
chemicals that sublimate
(change phases from solid
straight to gas)
Major Disadvantage
It is toxic and should be
used in well ventilated
areas.
How does it work?
Keeping a print on paper
in a closed container,
Iodine will react with the
oil in the print resulting in
a brownish print to
develop.
Iodine:
The print will fade quickly if
it is not fixed. This is done
with a solution of Calcium
Chloride and Potassium
Bromide in water. The print
will then last a few weeks.
Physical Developer
(silver nitrate AgNO3)
-used on porous articles that
might have been wet at one
time.
- can be used after iodine
fuming and ninhydrin
Disadvantages
- will destroy any traces of
protein from an object’s surface
(hence, no DNA collection from
the print)
Super Glue:
Discovered accidentally by a
civilian forensic scientist at the
U.S. Army Crime Laboratory in
Japan.
Super Glue:
Contains Cyanoacrylate which
is the ingredient that combines
with the print.
Major advantage :
You can use it to develop
prints on materials which
no other method will
work. ex. plastic
Super Glue:
Powders are unsuitable for
many types of plastic surfaces.
The powder tends to smear over
the plastic as if it were oily.
Another Advantage
It can develop “thin Prints” prints which only a trace
amount of material is
transferred from the finger to
the print. Super Glue can be
done after dusting is tried.
Fuming Tank
Other Development methods
• Magna Brush: a magnetic device which
allows you to dust a print with iron dust.
• Amido Black: a chemical which enhances
faint blood patterns.
• Ardrox & Basic Yellow: dyes which
absorbs into super glued prints. (helps
with photographing the prints)
• Crystal Violet: Used on the sticky side of
tape after a print is lifted to help visualize
Other Development methods
• DFO: 1,8,diazafluoren-9-onesimilar uses
as ninhydrin and amido black.
• Indanediones: similar to DFO and
ninhydrin.
• Leuco Crystal Violet: stain that enhances
bloody prints
• Ray: A mix of Rhodamine 6G, Ardrox,
and Basic Yellow. Put on prints to help
visualize.
Other Development methods
• Redwop/Greenwop: Fluorescent powders
which can be enhanced by high energy lamps.
• Small Particle Solution: a suspension of
molybdenum disulfide that can be sprayed on
porous surfaces.
• Stickyside Powder: a product of Japan. Made
to be applied to the sticky side of tape.
• Sudan Black: An industrial dye that is
absorbed into the print oils.