Fingerprinting

History of Fingerprinting:
Fingerprints were first used when ancient Babylonians used them on clay tablets for business transactions.  Thumb prints were also found in ancient China.

Then in the 14th century, a government official had discovered that no fingerprints were exactly the same.

Types of Finger Prints:

Direct: These prints are visible fingerprints that are left when things such as blood is on a finger which creates a print.  They are normally seen on smooth surfaces and no extra enhancements are needed to make them visible.

 Latent: These types of fingerprints are left at crime scenes, but aren't seen by the naked eye.  To identify these prints, you would have to use techniques such as using fingerprint powder.  When a finger touches a surface such as glass or a window, the sweat along with other compounds creates a fingerprint that is left behind.

Plastic: This is a print that is more easily visible then the others which leave behind because of the surface that was touched, such as fresh paint.  These fingerprints are three-dimensional.  Since there is already a 'mold' with the print, unlike the latent prints, plastic prints don't need techniques to make them appear.

 http://shs.westport.k12.ct.us/forensics/04-fingerprints/plastic_print.jpg

Techniques/Chemicals to Develop Prints:

Smooth/Hard/Nonabsorbent: Fingerprints left on surfaces such as mirror, glass, or tile are made visible with the use of power.  If a print is left behind on a light surface, you must use a darker fingerprint powder such as black powder which is composed of black carbon or charcoal.  Aluminum dust is a lighter colored powder which is applied to darker surfaces.

Porous/Soft: Fingerprints left on surfaces such as cardboard and paper are made visible with the use of chemicals.  For instance, once you apply a chemical silver nitrite, you can see the print using an ultraviolet light.

Basic Patterns of Fingerprints:

 Plain Arch: Hill shaped, has a curved top

 Tented Arch: Has a sharp curved top

 Ulnar Loop: A curved loop towards the pinky

 Radial Loop: A curved loop towards the thumb

 Plain Whorl: Has a circular shape whorl towards the center

 Central Pocket Loop: More oval than the plain whorl

 Double Loop: A loop that creates an 'S' shape

  Accidental Whorl: Has more than one type of pattern

Procedures for Collecting/Lifting Prints:

When you want to make latent prints visible, or lift plastic and direct prints, you could use fingerprinting powder.  This works with only smooth, hard, or nonabsorbent prints, otherwise you would use chemicals. 

1.  Dip the brush into the powder         

          - Light surface = dark powder

           - Dark surface = light powder 

2.  Tap the brush to get excess powder on the area of the print

3.  Gingerly blow off the powder but do not touch it

4.  Continue to apply the powder until the print is visible

           - The powder will stick to substances such as sweat

              and oil

5.  Use a magnifying glass to observe the fingerprint

That procedure would be used to make a fingerprint visible, but to lift one, you would need to continue the process below:

6.  Carefully lift the print with a piece of tape.

7.  Put it on a sheet to preserve the fingerprint

           - Dark powder = Light sheet

           - Light powder = Dark sheet

Sources:

 http://www.fingerprinting.com/types-of-fingerprints.php
http://onin.com/fp/fphistory.html
http://www.odec.ca/projects/2004/fren4j0/public_html/fingerprint_patterns.htm