There is so much romance in the concept and act of extracting fingerprints to solve crimes, thanks in part to the continuing popularity of crime shows on TV.  Fingerprint extraction is such an exacting science that it requires patience and a very meticulous system of collection in order to ensure that the sample collected is reliable.  For private investigation students, fingerprint extraction is one of the basic skills they will have to learn.

The purpose of fingerprint extraction
The ancient Chinese and Assyrians used fingerprints to establish identity when signing legal documents.  However, its use as a classification system started in 1823 and again in the late 19th century.  It was in the late 1800s when British police used fingerprints for the identification of criminals in Bengal, India.  Some 10 years later, the first fingerprint files in Britain was established.  From then on, the science of fingerprint extraction has progressed, becoming a very effective method of identification and a highly efficient tool for crime fighting.

Methods of collecting fingerprints

Fingerprint extraction by powder dusting
To collect fingerprints, one of the oldest methods used is by powder dusting the surface.  A forensic or crime scene technician will use very fine powder to dust an area.  This powder is spread with the use of a rounded brush or a magnetic wand.  If there are fingerprints on the surface, this powder will stick to the proteins that have been secreted by the fingers’ sweat glands.  The technician will then remove the excess powder to reveal any impressions that may have been left behind. 

In most cases, dark fine powder is used to dust for fingerprints prior to extraction.  However, there are cases when fingerprints are especially difficult to find, much less obtain.  On certain surfaces, such as Formica, crime scene technicians might use fluorescent powder – the very fine type – to dust the area.  In the dark, this powder will glow, allowing technicians to locate where the prints are and lift them from the surface using sticky tape.

Fingerprint extraction by fuming
The fuming method, or more completely the cyanoacrylate fuming method is one of the best tools ever developed for fingerprint extraction.  This is the preferred method when dealing with latent fingerprints.  It produces high quality results, which makes it one of the most trusted methods used by forensic and crime scene investigators.

The fuming method is a chemical technique for extraction of prints.  Since fingerprints are made up of sweat (which later evaporates) and other components, including inorganic chemicals and proteins such as sodium, chlorine , potassium, glucose, peptides, amino acids, ammonia, isoagglutinogens and riboflavin, the fuming method uses a special chemical that will react to these substances.  By changing the chemical composition of these substances, the prints become visible and can later be photographed for identification or comparison.

To extract fingerprints using this method, a crime scene technician takes the surface to be processed and puts it inside a tank that contains a built-in heater.  This tank is airtight.  The technician will then put several drops of cyanoacrylate on a container located at the bottom part of the tank, seal the tank and then turn on the heater until it reaches about 120F to 150F.  The gaseous form of cyanoacrylate will then react with the surface to show any fingerprints, if there are any.

The fuming method is actually not new.  It has been used in the Criminal Identification Division in Japan since 1978.  It was later imported from Asia by the United States Army Criminal Investigation and the Bureau of Alcohol, Tobacco and Firearms Laboratories.  Today, it is one of the most popularly used methods for fingerprint extraction used by professionals and is also highly recommended as a tool for private investigator students.

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