Forensics: Fingerprinting

What is Fingerprinting and When was it First Used in the United States?

     Fingerprinting is the science of taking a person's fingerprint in order to obtain personal identification. Forensic science has proven that the likelihood of two people having the same fingerprint is very slim. By finding a fingerprint at a crime scene it should allow scientists to narrow down on a suspect.

http://forensicpsych.umwblogs.org/research/criminal-justice/fingerprint-analysis/

     A man who went by the name of Gilbert Thompson who was a surveyor in New Mexico. In 1882 as a way to prevent forgery, placed his prints on a servey.

     The first use of fingerprinting in a criminal matter was obtained from prints obtained on a door post in 1892 by an Argentian Police Commondore named Juan Vucetich. 

http://onin.com/fp/fphistory.html

     After Congress permitted the F.B.I to establish an Identification Division in 1924 it became much easier to identify repeat criminals and missing individuals. Today, with the use of a computerized system the F.B.I  has a record of 34 million criminal fingerprints.

What Kinds of Fingerprints Are There?

There are 3 types of classified fingerprints: Patent, Plastic and Latent fingerprints.



Blood covered fingerprints are often
resembled as patent fingerprints



     Patent prints are visible prints seen with the naked eye that occur when a foreign substance on the skin of the finger comes in contact with the smooth surface of another object. The foreign substances contain dust particles which have collected on the ridges of the fingers, making these prints easily identifiable.

http://i.istockimg.com/file_thumbview_approve/5472104/2/stock-photo-5472104-fingerprints-and-glass.jpg



Plastic prints can be present on a
semi melted chocolate bar or on a
surface that has been freshly painted



     Plastic prints are visible, impressed prints that are form through the contact of a finger and a soft, malleable surface which result in an indentation.

taurusstudio.net

fingerprintanalyst.webs.com

     Latent prints are fingerprints formed from perspiration found in the sweat pores. When your fingers come in contact with body parts containing moisture, oil and grease they adhere to the ridges of the fingers and a film is created when your fingers come in contact with an object. Latent prints are the fingerprints used in this forensic project.

 Developing Prints on Different Surfaces & Lifting/ Collecting Prints 

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     With fingerprints on smooth surfaces the common way of making these prints visible is to dust with a powder that will stick to the fingerprint and create a contrast between the print and its background. Photographing the print or using lifting tape are two techiques used in collecting prints on smooth surfaces.

    

fotolibra.com

     Fingerprints on porous surfaces require a reaction with chemicals to appear because porous surfaces absorb the latent print causing dusting to become inefficient. Ways to reveal these prints is by making ninhydrin or diazafluorenone react to the amino acids in the fingerprint. The use of ninhydrin turns the amino acids either blue or purple making the print visible. Fingerprints that have reacted with diazafluorenone illuminate blue light, then they start to glow yellow. In order to collect the prints from the porous surface place the material in a plastic bag and then run the desired chemical tests on it. Make sure you are wearing  gloves while handling the evidence.    

Nonabsorbent material containing fingerprints should be processed and analyed in a lab as soon as possible because with excessive exposure to high temperature and humidity the fingerprints will being to disapear.

http://www.kitchen-countertop-options.com/images/solid-surface-countertop.jpg

     With the use of fingerprint powder, on a hard surface, prints with become visible and then will become removable with lifting table.

    

     

The Basic Shapes & Patterns of Fingerprints 

http://www.securityandsafetysupply.com/news/news36.htm

 Fingerprint Lifting Lab


     For the first part of the fingerprint lab I used corn starch to lift my latent print. In order to reconstruct this activity you must take your thumb, from either hand, and collect some of the moisture that is currently resting on your nose. Place your thumb on a darker surface, preferably black, and apply a fingerprint lifting technique with corn starch. Once the print is visible take a piece of tape, rotate it vertically and press lightly to collect the print. As you can see I was able to lift the print to the point of seeing the ridges of the thumb.

     

      The second part of this lab involved carbon/ graphite powder as another material to lift fingerprints with. The procedure for this activity is identical to the activity with corn starch. My test with the carbon/ graphite powder is slightly more difficult to read the prints because the powder has a greater particle size compared to the corn starch.