Fingerprint Latent Print Powders
One
of the chief duties of crime scene investigators is the recovery of
latent fingerprints. Latent fingerprints are those that are retrieved
from a scene as opposed to those fingerprints that are taken upon
request. Fingerprints are extracted from a surface with application of a
fingerprint powder, which is also known as fingerprint dust.
This process, commonly known as "dusting for prints", is familiar to
all of us who routinely follow the crime scene investigators of the
C.S.I. television series.
For fingerprint extraction, there are two basic types of dusting powder that can be used:
Regular Latent Print Powder:
Regular powder differs from magnetic powders in the respect that
magnetic powders contain iron and they adhere to a magnet. Regular
powder can be applied with success on such surfaces as windows,
televisions, kitchen counter tops, table tops, painted surfaces,
cabinets and many other surfaces found in residential and commercial
settings, and it is quite effective in dustings on apprehended or stolen
vehicles on painted surfaces on the exterior of the vehicle and on
glass.
It must be emphasized that the crime scene investigator
uses a color of powder in contrast with the background surface in order
to get a clear latent print. The colors available are black, white,
silver/gray and biochromatic. The black powder is the most popular of
the colors because the ridges of the print contrast against the white of
the backing card. The examiner then compares the latent black print to
the inked fingerprint that he is trying to match. Silver/gray powder
should be used on a dark background for
contrast
purposes. Most crime scene investigators carry jars of both colors and
two sets of black and white backing cards in their fingerprint kits.
Recently, a combination powder has been developed called biochromatic
powder which allows the latent prints to become easily visible on either
dark or light surfaces.
Regular powder is best applied to
surfaces using a fiberglass brush and, while the brush can be dipped
directly into the powder jar, it is advised that a small amount of
powder be sprinkled onto a tray in order to make the process less
cumbersome and in order to eliminate the possibility of knocking over
the powder jar.
Magnetic Powder: Magnetic powders are best
applied to shiny surfaces, such as plastic containers. When dusting for
fingerprints with magnetic powder, crime scene investigators must use a
magnetic applicator which has a magnet. Magnetic powder is applied with
a light hand with brushing strokes. Besides being available in the
colors of black, white, silver/gray and biochromatic, magnetic powder is
also available in fluorescent magnetic powder colors like red and
green. These can be used when dealing with problematic background
fluorescence, and they are best applied with feather duster.
Lifting Prints after Dusting:
Regular and magnetic powder are both effective in securing prints for
purposes of matching fingerprints. The process by which the fingerprints
are recovered from various surfaces at a crime scene is known as the
lifting process. Latent prints formed with either type of powder can be
lifted from surfaces by means of adhesive tape, either clear or frosted.
Simply apply a strip of tape to the powdered surface and rub it in to
ensure that the tape has made sufficient contact with the powdered
surface. Then, lift the paper from the surface and apply it to a backing
card with some pressure. Crime scene investigators must be careful to
log the critical data regarding the lifting of the fingerprints, such as
the date and military time, the location and any other information
unique to those prints that should be noted.
The employment of
fingerprint powder in the process of obtaining latent prints is critical
to the success of the undertaking. However, as with all technical
aspects of crime scene investigations, the application of fingerprint
powder is a skill that requires professional training, because human
technique is the final determining factor as to successful extraction of
an identifiable and matchable fingerprint.
Any questions call 714-979-1405 or email us at Sales@HittMarking.com