Fingerprint is an important evidence found at the crime scene, but in most of the cases, these are not visible to naked eyes. To make these visible we use different methods. Some of these methods are explained in this ppt. To know more about the topic, clink on the link- https://youtu.be/ky58Byef-D4

2. DEVELOPMENT OF LATENT FINGERPRINTS
USING POWDERS METHOD (PART-II)
By-
Vaishnavi Puli
Volunteer of Applied Forensic Research
Sciences

3. CONTENT
• Mechanism of technique
• Application procedures
• Regular powders
• Metallic powders

4. MECHANISM OF TECHNIQUE
• The application of finely divided material and the subsequent removal of the excess powder by
brushing, blowing or tapping has been the universal method of intensifying fingerprints on Non-
absorbing surfaces. Since the early days of fingerprint technology.
• The technique relays on the mechanical adherence of fingerprint powder to the moisture and oily
components of the skin rich deposit.
• The adhesion of powder formulation to fingerprint residues is governed by the “Pressure deficit
mechanism”
• If a powder partical is wetted only on its lower side by the sweat deposition , then going to the
curvature if meniscus there will be a pressure deficit causing the particulate to adhere or stick.
• The effectiveness with the powder adheres on the ridges depends on the size and shape of the particles
that compose the formulation i.e., the formulation of the powder. The small fine particles adhere more
easily than large coarse ones. Therefore, most formulations are composed either very fine rounded
particles that about one micrometer in diameter Or a fine flake particles about 10mm in diameter. Nano
particle size powder compositions have proved to be very effective in lifting fingerprints.

5. • A sample fingerprint developed with the aid of nano
particle based composition incorporating crystal
violet stain.
• As the age of the fingerprints residue increases the
moisture and the oily components tend to evaporate
leaving the deposition more viscous. The same
phenomenon is observed in warm climate areas also.
• Thus, aged prints in tropical climates are literally
difficult to develop by powder technique or powder
method.
• The drying rate is however not dependent on the
relative humidity indicating that sweat residue has
low water content near the surface.
Crystal Violet dye stain

6. APPLICATION PROCEDURES
We are going to study about application procedures of these powders:
• Before the application of powder formulation the surface should be
searched visually for the fingerprint impression. This is usually aid of an
intense light source in consult with the magnifying glass. The light source
is put at an oblique angle ( other than 90 degrees angle) to the surface
suspected of bearing the latent fingerprint and viewed with the help of
magnifying glass.
• The print sholud first photographed using an appropriate filter next the
relevant powder should be applied in a circular motion by a fingerprint
brush. Generally the fingerprint brush is made up of camel hair or from
glass fibres. The important thing is to be notes here that this brush can
only be used with non-magnetic powders here should be taken to prevent
dismatching of the imprint.
• Excess powder should than be removed of by dusting the surface with
gentle tapping or blowing.
• The developed print sholud once be photographed. Finally, it sholud be
lifted with a tape and preserve for record.
Magnifying glass
Tape lifting of fingerprint

7. • Application if powder to fingerprint by brushing is well established technique. But
has one disadvantage i.e., contact of the brush with the fingerprint has an inevitable
destructive effect so that degree of cautious is required by the fingerprint expert.
• It has been estimated that about 10% fingerprints developed at the crime scene using
conventional powders dusting procedures are difficult to identify.
• Powder may be applied without using a brush an electrostatic depositer automizer
or aerosol spray may be used instantly for electrostatic deposition. The powder is
placed on the surface of an electrode held above the surface of the fingermark.
• A potential gradient of about 10k watt is maintained between the electrode and the
surface of the powder on the electrode becomes charged to the polarity of the
electrode and is accelerated towards the surface where it is discharged and aquires
the polarity of the surface. The excess powder is attracted back to the electrode and is
discharged there.
• Magna brushes and magna powders may also be used to avoid the problem of
smudging.
• Magna powders are made by incorporating quartz the spherical iron particles in the
conventional powders.
• The magnetic iron acts as a carrier for the non-magnetic formulation forming a brush
when the powder is picked with a magnetised applicator.
Magna brush

8. • On brushing the imprint impression only fine particles of the formulation
adheres to fingerprint residue.
In simple terms one can also say that the magnetic wand
when taken near to the magnetic powder, because of the creation of the
magnetic field results in the formation of bristles at the tip of the wand which
acts as brush and this can directly develop the latent fingerprints. Once the
print has been developed the excess powder can be detached from the
applicator by drawing the magnetised steel rod .
• To improve the performance the magna powder can be replaced by
magnetic flake particles also. In such formulations the coarse iron particles
are replaced by magnetic plates that are attracted to the magnetic applicator.
Unlike standard magna powders which contain only about 1% if fine
particles that can adhere to the fingerprint residue.
• All the magnetic plates lifted by applicator are available for fingerprint
development. The magnetic flakes are specifically useful for print
development on rough and porous surfaces such as painted walls , polythene
and paper.
Magna powder

9. REGULAR POWDERS
• Regular fingerprint powder consist of resinous polymer for the adhesion i.e., for the sticking
property and a colourent for contrast the adhesive gets adherse to the moisture and oily
components of the sweat residue by pressure deficit mechanism.
• While the colourent and the color particles get absorbed on the adhesive in this manner the
ridge pattern is visualised.
• The commonly used adhesives are starch, kaolin, rosin and silica gel.
• The colourent may be an inorganic salt or an organic derivative which imparts color to the
ridges.
• Formulation containing Ferric oxide and rosin, Manganese Dioxide and rosin, Titanium and
kaolin, Lamp black, Pullers earth are common examples of inorganic based fingerprint
powders.The working performance of the composition may be improved by coating powder
on to fine quartz or plastic particulates .
• A black powder containing iron oxide , quartz, kaolin and carbon soot is an example of
“coated dusting formulation”.

10. • Over the years it became evident that commercial fingerprint
powders containing inorganic salts of Mercury, Cadmium,
Titanium, lead , Manganese etc… pose an occupational
hazard to the user
• As a result the organic based formulations became more
popular. These formulations generally contain an organic dye
as the colourent. For improved results florescent and Lazer
active dyes are used. Formulation containing flourscent eosin-
Y and rhodamin-B are some common examples of organic
based fingerprint powders. These florescent powders works
well with the UV light sources and multiwatt lasers. The
mean advantage of these powders is that they can used on
contrasting surfaces. They also come in Magnetic and Non-
magnetic forms.
• These florescent powders react with the UV or Purple or Blue
bands of Visible light to produce different clues that can be
easily detected. Here should be observed by using coloured
googles such that the wavelength of light emitted from the
UV source doesn’t hump the eyes.
• Ostrich brush used to sprinkle this flourscent powders on the
latent fingermark.
Fingerprints developed using
flourscent powders
Ostrich Brush

11. METALLIC POWDERS
• Powder formulation containing meshed “metals” have been in use for a considerable time .
• There advantage is that they have “longer shelf life” as compared to the organic based powders
• There disadvantage is that metallic components “elicit toxic effects” to the users .
• Silver powder containing “aluminum flaked and quartz powder”.
• Gold powder containing “bronze flakes and powdered quartz”.
• Grey powder containing “ meshed aluminum and kaolin” .
• The above mentioned powders are some of the examples of metallic dusting compositions.
• Fine Lead powder has been used for latent detection of “X-ray electronography and auto-
electronography”.
• A good number of powder formulation contain natural or synthetic organic derivatives that flourish
ir phosporis upon exposure to UV light or the Lazer light.

12. • The advantage of such compositions is that they are useful for visualisation
of latent fingerprints deposited on multi-colored surfaces that would present
a contrast problem if developed with conventional powders.
• Moreover, these can be used for developing weak prints also.
• The disadvantage is that these can be rarely used in field work.
• Some formal organic compounds which have being used for powders are
accredin-yellow, accredin-orange, cumerin-6, Crystal –Violet, Nile-blue,
rhodamin-B, rhodamin-6G.
• Luminiscebt powders containing lanthanide complex in place of organic
derivatives have also been formulated
• . Lanthanide complexes offers advantages including benefits
from large Stokes shaped, long luminescent life times, narrow emissions,
ability if sequential assembly of complexes and chemical variability of
legets. Moreover such powder’s are suitable for detection of latent
fingerprints on difficult surfaces such as wood, masking tape and polythene

13. MCQ TIME
• Which metallic powder is containing “Meshed
aluminum (Al) and kaolin”?
A. Silver powder
B. Grey powder
C. Gold powder
D. None of the above

14. Thank You