Transcript print development

LATENT FINGERPRINTS
FLTCC Forensics
UNT in partnership with TEA, Copyright ©. All rights reserved.
2
Latent Prints

Fingerprints are formed from material on the
fingers that is pressed upon a surface.



1. Prints are also formed from oils secreted by the
fingers.
2. Through the pores, perspiration is discharged and
deposited on the surface of the skin.
Once the finger touches a surface, perspiration, along
with oils that may have been picked up by touching
the hairy portion of the body, is transferred onto that
surface.
Latent Prints

A fingerprint is an individual characteristic;
no two fingers have yet been found to
possess identical ridge characteristics.

The FBI has nearly 50 million fingerprint
records in its computer database and has yet
to find an identical image belonging to two
different people.
COMPOSITION
OF FINGERPRINTS

Sweat
99.0-99.5 % water
 0.5-1.0% solids

50% organic solids (mostly amino acids)
 50% inorganic solids (NaCl and KCl)


Contaminants
Bodily fluids (blood, saliva, nasal
secretions, semen, etc.)
 Oils and fats (sebum)

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THREE TYPES OF
FINGERPRINT IMPRESSIONS

Patent fingerprints – visible prints left on a
smooth surface when blood, ink, or some other
liquid comes into contact with the hands and is
then transferred to the surface
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THREE TYPES OF
FINGERPRINT IMPRESSIONS
(CONTINUED)

Plastic fingerprints – actual indentations left
in some soft materials such as clay, putty, wax,
or dust.
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THREE TYPES OF
FINGERPRINT IMPRESSIONS
(CONTINUED)

Latent fingerprints – fingerprints that are
invisible to the naked eye and caused by the
transfer of oils and other bodily secretions onto a
surface. They can be made visible by various
different methods
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Latent prints are impressions left by friction ridge skin on a
surface, such as a tool handle, glass, door, etc.
Prints may be collected by revealing them
with a dusting of black powder and then
lifted with a piece of clear tape.
Did you know? Camel hair is the most common animal
hair used to make fingerprint brushes. Now many
brushes (like the one above) are made out of fiberglass.
DEVELOPMENT OF
LATENT PRINTS
Some investigators use fluorescent powder and UV lights to help
them find latent prints on multi-colored or dark surfaces.
Magnetic powder can also be used to reveal latent prints. This
type of powder works better on shiny surfaces or plastic baggies
or containers.
The cyanoacrylate fuming method (often called the super glue
method) is a procedure that is used to develop latent fingerprints
on a variety of objects.
Ninhydrin is a chemical that bonds with the
amino acids in fingerprints and will produce a
blue or purple color. It is used to lift prints from
surfaces such as paper and cardboard.
Click the icon to
view the Crime 360
Super Glue Video
Top Left: http://www.stapletonandassociates.com/images/MagPowder.jpg
Bottom Left: http://www.ok.gov/osbi/images/ninhydrin%20print.jpg
Bottom Right: http://www.forensicsrus.com/images/SupergluePrint.jpg
Latent Prints

A variety of techniques use powder and
chemicals to develop latent fingerprints.

A. Lifted fingerprints
1. Formed when a piece of adhesive tape is
placed over a developed latent print and pulled
away.
 2. The latent print adheres to the tape and then the
tape is placed upon a glossy white or black “latent
lift backer” card.

Latent Prints

3. Photography is used during the development
and lifting process.
Latent Prints

Techniques range from chemical methods
such as powders and iodine fuming to the
use of laser light.

Fingerprint powders

The powders, when applied lightly to a
nonabsorbent surface with a camel’s-hair or
fiberglass brush, readily adhere to perspiration
residues and/or deposits of body oils left on the
surface.
Latent Prints – Fingerprint
Powder with Fiberglass bush
Latent Prints – Fingerprint
Powders

Experienced examiners find that gray and
black powders are adequate for most
latent-print work

1. Gray powder, composed of an aluminum
dust, is used on dark colored surfaces. It is
also applied to mirrors and metal surfaces.
Latent Prints – Fingerprint
Powders

2. The black powder, composed basically of
black carbon or charcoal, is applied to white
or light colored surfaces.

3. Fluorescent powders are also used to
develop latent fingerprints. These powders
fluoresce under ultraviolet light.
FINGERPRINT POWDERS



Applied lightly to a
nonabsorbent surface
with a soft brush.
They readily adhere to
sweat residues and/or
deposits of body oils left
on the surface.
Investigators need to
prevent damaging the
print when trying to
develop it
Did you know? Camel hair is the most common animal
hair used to make fingerprint brushes. Now many
brushes (like the one above) are made out of fiberglass.
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FINGERPRINT POWDERS
(CONTINUED)
Gray and black powders – the most
common, chosen to make the best contrast
with the surface
 Fluorescent powders – used to
photograph latent prints on multi-colored
surfaces. They fluoresce under ultraviolet
light.

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FINGERPRINT POWDERS

(CONTINUED)
Magnetic powder –
magnetic powders are
applied with a magnetic
brush

Allows for very delicate
application of powders,
decreasing chances of
scratching prints with
bristles
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THINGS TO CONSIDER ABOUT
FINGERPRINT POWDERS…




Fineness
 The powder must be fine enough to show the detail of the fingerprint.
Finer powders would be theoretically capable of displaying greater
detail than coarser powders.
Adhesion
 The powder must display the right level of adhesion, so that it will
adhere to the residue of the fingerprint (often oils) and not adhere to
the rest of the surface where it would obscure the view of the print.
When a powder coats a surface, this is known as 'painting'.
Sensitivity
 Sensitivity is related to adhesion, and is how well the powder adheres
to a surface. For example, aluminum flake is more sensitive than
aluminum powder, but greater sensitivity is not always desirable.
Color The fingerprint powder must be a suitable color for the surface
in question.
Flow
 To a lesser extent, it is important that the powder can flow, and does
not 'cake' into a solid block, which would render it useless.
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FINGERPRINT CHEMICALS
(CONTINUED)
DFO (1,8-diazafluotrn-9-one) –
newer replacement chemical for
ninhydrin. It is 2.5 times more
sensitive than ninhydrin.
 Rhodamine 6G is a fluorescent dye
that may be used after
cyanoacrylate fuming to visualize
latent prints under laser light.


Once fluorescent dyes are applied,
fingerprints can then be visualized
using an Alternate Light Source
(ALS) in an effort to enhance ridges
and minimize background
interference
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FINGERPRINT CHEMICALS
(CONTINUED)
Gentian violet (or crystal
violet) – used for developing
latent prints on the adhesive side
of tape. An aqueous solution of
crystal violet is sprayed directly
onto the adhesive.
 Wetwop is another solution
developer that can be used on
adhesive surfaces.

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FINGERPRINT CHEMICALS
(CONTINUED)

Amido Black – protein dye stain that can
develop faint bloody fingerprints on porous and
nonporous surfaces. Blood must be swabbed
prior to amido black application for any DNA
analysis
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FINGERPRINT CHEMICALS

(CONTINUED)
LCV (Leuco Crystal Violet) – a protein stain
spray that can develop faint or invisible bloody
fingerprints on non-porous surfaces
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LUMINOL
A chemical that reacts with hemoglobin to
produce the phenomenon of chemiluminescence
(same as fireflies!)
 Can be sprayed where nothing is visible. Under
UV light, blood or bodily fluids glow

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OTHER CHEMICAL
DEVELOPERS…
Sticky-side powder – paste made with powder
that is used after cyanoacrylate fuming and on
the sticky side of tape
 Basic Yellow 40 – another fluorescent technique
for nonporous surfaces or post-cyanoacrylate
fuming
 DAB – Diaminobenzidine formula – another
blood enhancement technique
 Small particle reagent – useful on wet surfaces
such as plastic bags or coated surfaces – adheres
to the fatty deposits in fingerprints

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PRESERVATION OF
DEVELOPED LATENT PRINTS
Photograph!!
 Covering the print to preserve it in its entirety (if
on a small object)
 Lifting the prints with adhesive tape and placing
the tape with prints on a card with labels

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Fingerprints > Analysis
Chemical Development:
Iodine Fuming



Iodine sublimes
(solid → gas)
Iodine reacts with lipid
components; becomes
trapped in the print.
Fuming wand or chamber
Dirty Brown Color
Latent Prints – Iodine Fuming

Of the several chemical methods used for
visualizing latent prints, iodine fuming is
the oldest.

Iodine is a solid crystal that, when heated,
transforms into a vapor without passing
through a liquid phase; such transformation is
called sublimation.
Latent Prints – Iodine Fuming

Most often, the suspect material is placed
in an enclosed cabinet along with iodine
crystals.

As the crystals are heated, the resultant
vapors fill the chamber and combine with
constituents of the latent print to make it
visible.
Latent Prints – Fuming Cabinet
Latent Prints – Iodine Fuming

Iodine prints are not permanent and begin to
fade once the fuming process is stopped.
Must photograph immediately on development.
Prints can be fixed with a 1 percent solution of
starch in water, applied by spraying.
FINGERPRINT CHEMICALS

(CONTINUED)
Iodine fuming – one of the oldest latent print
development methods. Solid iodine crystals
sublimate and the vapor will react with fatty oils
and some sweat residue. Iodine prints are not
permanent and will begin to fade once the fuming
process is stopped. Can be used on porous and
nonporous surfaces
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FINGERPRINT CHEMICALS

Ninhydrin – reacts with amino acids in sweat to
form purple-blue prints. A 0.6% solution (in
ethanol) is sprayed onto porous surfaces such as
paper.
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Fingerprints > Analysis
Chemical Development:
Ninhydrin



Reacts with amino acids; purple color
Painted or sprayed on area
Heated to react
amino acids in fingerprints
R
O
H2N
OH
C
COO
O
O
H
N
OH
O
Ninhydrin
O
O
Ruhemann's Purple Complex
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Latent Prints - Ninhydrin




For most fingerprint examiners, the chemical
method of choice is ninhydrin.
Its extreme sensitivity and ease of application
have all but eliminated the use of iodine fuming.
Ninhydrin is a chemical reagent used to develop
latent fingerprints on porous materials by
reacting with amino acids in perspiration.
It is commonly sprayed onto the porous surface
from an aerosol can.
Latent Prints - Ninhydrin

The development of latent prints with
ninhydrin depends on its chemical reaction
to form a purple-blue color with amino
acids present in the trace amounts in
perspiration.

Generally, prints begin to appear within an
hour or two after ninhydrin application.
Latent Prints – Physical
Developer

Physical developer is a silver nitratebased reagent formulated to develop
latent fingerprints on porous surfaces.

This technique is very effective for
developing latent fingerprints on porous
articles that may have been wet at one
time.
FINGERPRINT CHEMICALS


(CONTINUED)
Physical Developer – silver nitrate-based liquid reagent
used on porous surfaces. It is often used as the last resort
because it destroys protein.
Cyanoacrylate (superglue) fuming – developed in 1982
by Japanese Police. It is used on a variety of materials not
only to visualize latent prints, but also to semipermanently affix them to the surface. Works best on
nonporous surfaces. Can be developed further with
powders or fluorescent dyes
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Fingerprints > Analysis
Chemical Development:
Super glue fuming



Fumes with heat or base (NaOH)
Fumed in cabinets
Off-white print
Latent Prints – Super Glue
Fuming

Super glue fuming is a technique for
visualizing latent fingerprints on
nonporous surfaces by exposing them to
cyanoacrylate vapors; named for the
commercial product Super Glue.
Latent Prints – Super Glue
Fuming

Super glue is placed on absorbent cotton
treated with sodium hydroxide. The fumes
can be fumes can also be created by
heating the glue.

The fumes and the evidential object are
contained within an enclosed chamber for
up to six hours.
Latent Prints – Super Glue
Enclosed Chamber
disposable cartridges containing
cyanoacrylate
Wand can be used at Crime
Scene to develop prints
Latent Prints – Super Glue
Fuming

Super glue is approximately 98 to 99
percent cyanoacrylate ester, a chemical
that interacts with and visualizes a latent
fingerprint.

Development occurs when fumes from the
glue adhere to the latent print, usually
producing a white-appearing latent print.

SUPERGLUE FUMING
https://www.youtube.com/watch?v=FkcSkADVMIM
UNT in partnership with TEA, Copyright ©. All rights reserved.

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Fingerprints > Analysis
Chemical Development:
Ninhydrin and super glue prints can be
further processed:


Dusted
Chemically treated to
fluoresce (using laser
or alternative light)
Preservation of Developed Prints

Once the latent print has been visualized,
it must be permanently preserved for
future comparison and possible use in
court as evidence.

A photograph must be taken before any
further attempts at preservation.
FACTORS AFFECTING
FINGERPRINTS
Age – thinner epidermis, flattening of dermal
papillae, creases, etc.
 Fine ridge structure – less skin contact leads
to a spotty appearance.
 Stimuli – sweating can be due to warmth,
exertion, fever, drugs, anxiety, tension, pain, or
spicy foods.
 Occupational and medical condition –
teaching, and other positions in which a person
handles or shuffles papers, can cause fine ridge
structure.

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FACTORS AFFECTING
FINGERPRINTS
(CONTINUED)

Transposal factors






Receiving surface texture
Contaminants on the hands
Contaminants on the receiving
surface
The manner of contact
The amount of pressure
Environmental factors
Temperature
 Humidity
 Handling

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TRENDS WITH FINGERPRINTS
It is NOT possible to determine the age, sex or
race of an individual solely from their
fingerprints. However:
 Statistically in young adults, friction ridges of
women are significantly finer than those of men.
 Fine ridges may be found in the very young and
the very old.
 Manual labor tends to strengthen ridges.
 Women tend to perspire at a lower rate than
men.
 Sodium chloride (NaCl) is lower for women.
 Creases are more common in women's FPs.

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AFIS
Database of fingerprints taken from arrests
and unknown fingerprints found at
unsolved crime scenes
 Investigators enter both known and
unknown prints and identify the minutiae
 When an unknown print is entered into
AFIS, the minutiae are identified and the
computer crosses them with known
offenders
 THE INVESTIGATOR MAKES THE LAST
DECISION on a match

55
Fingerprints
Modern Fingerprint Analysis

Computer system stores patterns and
minutiae of prints

AFIS: automated
fingerprint identification
system
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AFIS
http://www.youtube.com/watch?v=ZKi1CKTRCQM&feature=r
elated

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
https://www.youtube.com/watch?v=tqFzVfPRd5s
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LATENT PRINT DEVELOPMENT
61
Fingerprints > Collection
Collection of prints:
Tape lift:


Tape placed over developed print
Tape then placed on white card.
Fingerprints > Collection
Collection of prints:
Sometimes a photograph will be the only
permanent record.

https://www.youtube.com/watch?v=j2BcxTW_EV
Q#t=90
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LATENT PRINT COMPARISON
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