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Fingerprint Processing and
Photography
Professor Mike Wiehe
Goals
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Students will receive a brief background
about latent prints
Traditional latent print recovery techniques
will be discussed
Students will learn about new chemical
processes utilized today
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A fingerprint is the impression made by the
papillary ridges on the ends of the fingers and
thumbs. Fingerprints afford an infallible means
of personal identification, because the ridge
arrangement on every finger of every
human being is unique and does not alter
with growth or age.
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Ridges
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Each ridge of the epidermis (outer skin) is
dotted with sweat pores for its entire length and
is anchored to the dermis (inner skin) by a
double row of peglike protuberances, or papillae.
Injuries such as superficial burns, abrasions, or
cuts do not affect the ridge structure or
alter the dermal papillae, and the original
pattern is duplicated in any new skin that
grows.
An injury that destroys the dermal papillae,
however, will permanently obliterate the ridges.
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Latent Fingerprinting
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Involves locating, preserving, and identifying impressions
left by a culprit in the course of committing a crime.
In latent fingerprints, the ridge structure is reproduced
not in ink on a card but on an object in sweat, oily
secretions, or other substances naturally present on the
offender's fingers.
Most latent prints are colorless and must therefore be
"developed," or made visible, before they can be
preserved and compared.
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Latent Fingerprinting
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This is done by brushing them with various powders
containing chalk or lampblack combined with other
agents.
The latent impressions are preserved as evidence either
by photography or by lifting powdered prints on the
adhesive surfaces of tape.
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Three Kinds of Crime Scene Prints
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LATENT PRINT (hidden print) is a misnomer but often
used inclusively. There are actually three kinds of crime
scene prints. These are:
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1. VISIBLE PRINTS which are prints made by fingers touching a
surface after the ridges have been in contact with a colored
material such as blood, paint, grease, or ink.
2. PLASTIC PRINTS which are ridge impressions left on a soft
material such as putty, wax, soap, or dust.
3. True LATENT PRINTS which are invisible print impressions
caused by the perspiration on the ridges of one’s skin coming in
contact with a surface and making an invisible impression on it.
Perspiration contains water, salt, amino acids, or oils and easily
allows impressions to be made.
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Conditions Affecting The Quality
Of Latent Prints
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The surface on which the print is deposited
The nature of the material contaminating the fingerprint
Any physical or occupational defects of the person
making the print
How the object on which the prints appear was handled
The amount of the contamination
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Methods Of Developing
Latent Prints
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Traditional powders
Fluorescent Powders
Chemicals
Cyanoacrylate of superglue fuming
Visualization under:
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Laser
Alternative light
Ultraviolet illumination
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Most Effective Techniques for the Detection of Fingerprints
Surfaces
• Visual Examination
All
• Powders
Smooth
• Ninhydrin
Paper, Cardboard, Wood etc
• Sticky-Side Powders
Adhesive Tapes
• Physical Developer
Wet paper
• Fluorescence
Various
• Superglue + Fluorescence
Polythene, Plastic molding, etc
• Amido Black
Fingerprints in Blood
• Acid Yellow
Fingerprints in Blood
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Typical Exhibits from Crime Scenes
For each surface there is usually one most productive technique which can be used
on less important cases to save time
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Typical Exhibits from Crime Scenes
Superglue + Basic
Yellow 40
Sudan Black
Gentian Violet
Small
Particle
Reagent
Amido Black
Ninhydrin
For each surface there is usually one most productive technique which can be used
on less important cases to save time
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Powders - Can be effective on some surfaces
but must use best powders
Synthetic fibre,
animal hair and
glass fibre
brushes in use
Hundreds of
types of powder
available
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
Home Office Test Programme
Assessment of the
effectiveness of
different powders and
brushes on typical
surface
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Using 20 to 30 donors and
investigating performance on
different types of surface over
varying periods of time
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Ninhydrin
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It was not until the mid 1950's that it was discovered that ninhydrin
could be used to develop latent prints on porous surfaces.
When ninhydrin comes into contact withamino acids in fingerprint
residue, the reaction yields a red to purple print.
Effective on virtually any porous surface, ninhyrdin is most
appropriate for paper.
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Ninhydrin
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Ninhydrin Used On Bloody Shoe Print
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BEFORE
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AFTER
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Use of Amino Acid Reagents at
Crime Scenes on Wallpaper
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Amido Black
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Aqueous Amido Black is a protein dye solution sensitive
to the protiens in blood and other substances.
It will not react with the typical proteins found in latent
prints.
Applied to non-porous materials such as plastic, glass or
metal.
It is a corrosive chemical, recommended to do
presumptive blood test and DNA collection prior to
application
Photographs easily on light surfaces, utilize a forensic
light source if located on a dark surface.
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Amido Black
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Acid Yellow 7
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Acid Yellow 7 stain is one of the newer and more
effective fluorescent stains used to enhance bloody
footwear and fingerprint impressions on nonporous
surfaces.
Staining reveals a yellowish colored print which
fluoresces under blue-green light (400-490 nm).
When lifted with a white gelatin lifter the impression will
often reveal enhanced fluorescence.
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Fingerprints in Blood
Acid Yellow 7 Bloody Fingerprint on Glass Bottle
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Superglue Chamber for Fingerprints on Plastics
Enhanced with fluorescent dyes
Treatment Chamber
The fingerprint deposit initiates the growth of fibrous
deposit from ethyl cyanoacrylate vapor under conditions
of high humidity; this is visible as a white deposit which
may be enhanced with fluorescent dyes
Developed Fingerprint
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Making Fingerprints Fluoresce
Chemically developed prints can sometimes be
difficult to see and photograph
A number of fluorescent reagents have been
developed for the visualisation of fingerprints
Some dyes may be used to enhance chemically
developed fingerprints
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High Intensity Light Sources
Crimescopes and Lumalites
use very similar or identical
arc lamps to locate latent
prints
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A Solid State 532 nm Laser in Use
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Alternate Light Source Accessories
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Iodine Fuming
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Iodine crystals give off vapors that adsorb physically to
the oil and fat substances of a fingerprint
Use on porous and non-porous surfaces with fresh prints
Developed prints are not fixed and need to be
documented
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Physical Developer
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Physical developer is a reagent that reacts with
the lipids, fats, and oils, which are present in
fingerprint residues
Typically used after Ninhyrdrin and the forensic
light source
Photograph after each step
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Specific Reaction - Catalysis/Initiation
Fingerprint Deposits Developed with ‘Physical Developer’
Latent fingerprint on paper initiates
deposition of silver from a surfactant
stabilised silver nitrate solution
Will even detect fingerprints on paper
soaked in water for weeks
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Physical Developer Processing
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Small Particle Reagent
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It is a physical development technique where small black
particles adhere to the fatty substances left in fingerprint
residue
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Most well known for its ability to develop latent prints on
wet surfaces, such as vehicles wet with rain
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Can spray it on a surface or dip an object in it
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Photograph any latent prints then dried prints can be
lifted using traditional methods
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Small Particle Reagent
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Sequential Processing
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There is a large variation in the chemical
constituents of fingerprints from different
people
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There is also a large variation in the
amount of latent fingerprint deposit
between different people
The deposit from the same person also
varies from day to day and hour to hour
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Using one technique after another can
therefore produce additional fingerprints
The processes must be used in the
correct sequence
Different surfaces require different
sequences of process
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Sequential Processing
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Different types of surface
require different treatment
sequences
Use of one process after
another can double numbers
of developed fingerprints
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Typical Police Fingerprint Laboratory
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