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 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 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.
The two leading brands in the United States for fingerprint powder are Sirchie
and Lynn Peavey
Sirchie Fingerprint Laboratories
was founded in 1927 in Philadelphia by Francis Sirchie and has been providing forensic supplies to the law enforcement community ever since.
Lynn Peavey Company
is based in Kansas and has been a leader in the evidence collection industry since 1951.
These two businesses manufacture both regular and magnetic powder. Use the link below to order fingerprint powder online from Amazon and browse other fingerprinting products.