Finger Print Analysis

History of Fingerprinting

            While it is difficult to predict the exact time in which the first fingerprint analysis was used forensic scientists have managed to uncover fingerprints dating back to the 3^rd century B.C. This documentation was from ancient china in which thumb prints were found to be used in business transactions as a seal of approval. Another ancient use was in Persia where government officials used fingerprints for documents as they denoted no two fingerprints were the identical.

            The first interest taken in fingerprints in the western world was in 1684 when Dr. Nehemiah Grew documented the basic structure of fingerprints including ridges spirals etc. In 1880 Dr. Henry Faulds was credited with the first identification of a fingerprint found on a greasy alcohol bottle. By 1892 Sir Francis Galton developed the very first classification system of fingerprints.

Around 1846 the FBI has developed AFIS technology for classifying and sorting through the hand cards of fingerprints revolutionizing the use of prints in crime solving. By 1911 the first person to be convicted based primarily off finger print evidence in the western world was of a murder which occurred during a burglary. Charles Hiller had awoken one night to find that a light he had left on that night had been extinguished, upon investigating the house he came face to face with an intruder who reacted by shooting Charles twice killing him. When police investigated the seen they saw four fingerprints near a window imprinted on freshly painted veranda. Police eventually traced these prints to Thomas Jennings who upon this evidence managed to put on trial. The evidence was scientifically indisputable which led to Jennings conviction and execution.

Types of Finger Prints

            As there are different circumstances there are different types of finger prints, the three primary ones are latent prints, direct prints, and plastic prints.

Latent prints are prints that are not readily available to the naked eye as well as they are often left behind on unknowingly. These marks are usually the result of natural oils secreted from the body which can be accumulated on the fingers via friction. Once a criminal (or anyone) touches an object the adhered oils will leave behind an imprint of the finger which forensic scientist can then reveal with various techniques.

            Direct prints are much more easily identified as they are not as concealed as latent prints. Direct prints are prints left behind from other substances such as blood, or fresh paint as well as dirt left on a person’s finger. These types of prints leave behind much more noticeable residue and therefore do not need any special treatment to reveal.

          Lastly we have plastic prints which leave three dimensional marks. Plastic prints only occur when a person’s finger presses into a relatively soft/impressionable substance such as wax or putty and can even be left behind in dust. Since they leave direct indentions plastic prints do not require special equipment to locate.

Basic Shapes/Patterns

            Even though all fingerprints are different they all have basic patterns that they follow These basic patterns are broken into 3 main groups; loops, whorls, and arches.

Loops

            Loops are classified as fingerprints with ridges coming in from one side then curving back out towards the side they came.

            Radial loops- Loops that form downwards and curve towards the radius (thumb side)  

            Ulnar loops- Loops that flow towards the ulnar (little finger side). Ulnar loops are more common than radial loops.

Whorls

            Whorls are fingerprints with a circular pattern originating from a core. Whorls are approximately 35% of the patterns found in fingerprints and can be broken down into 4 main categories.

Plain whorls – which are composed of multiple circles like a bull’s eye target.

Central pocket loop whorls – Whorls that resemble a loop with a plain whorl towards the center.

Double loop whorls –  This fingerprint looks as if two loops collided forming an ‘S’ like pattern.

Accidental loop whorls – These whorls don’t fit in with the other categories, however they still have a core and resemble a warped whorl.

Arches

            Arches are the final type of fingerprint type, they are classified by ridgelines that rise in the centre and create a wave like pattern. They are the least common type of fingerprint pattern making up only 5% of the populations prints.

Plain Arch- Plain arches have only a slight rise towards the center in their wavelike pattern.

Tented Arch- Similar to plain arches only with a higher rise in the wave pattern.

Techniques for developing and collecting prints

            Once a forensic scientist understands the basics of fingerprints they must be able to develop them to a state where they can be analyzed as well as lifting them for research later. To do this there are a variety of methods using various chemicals the first of which we will discuss is the most commercially known, fingerprint dusting.

            Fingerprint dusting is used to identify latent prints on non-porous surfaces such as glass, tiles, and metal. This method usually makes use of black power (made from carbon or charcoal) and grey powder (made from aluminium or titanium powder). The fine powder sticks to the oil residue left behind by the print. Once the print is revealed it is either preserved photographically or lifted with a sticky tape. The con of this method is that it has to be done fairly shortly after the fingerprints are left as the oils in them dry out with time.

            Another method that can be used on hard surfaces involves the use of chemicals. This method is the combination and heating of super glue (which is mostly composed of cyanoacrylate) and sodium hydroxide. The fumes from this heated mixture bond with amino acids which are found in the oils on the print and make a hard print which can then be photographed and analyzed.

            If the print is not on something as hard and smooth as glass or metal this method

involving ninhydrin (triketohydridenehydrate). By exposing a porous surface (i.e. cardboard)

 to  this chemical the chemical slowly reacts with the oils and proteins in the fingerprint.

After several hours a purplish-blue print will appear. While slow this method can be used

even a while after the prints were made.

Bibliography

http://www.northants.police.uk/default.aspx?id=8447

http://www.clt.uwa.edu.au/__data/page/112506/fsp07_fingerprinting.pdf

http://jbertarioniforensics.blogspot.com/2009/08/plastic-fingerprints.html

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

http://willpollock.com/files/category-ascribe.net-preview.html

http://shs.westport.k12.ct.us/forensics/04-fingerprints/fingerprint_detection.htm

http://siciliamo.blogspot.com/2010/04/bloody-handprint-447-years-on.html

http://onin.com/fp/

http://viewzone2.com/fingerprintx.html

http://itsachemicalworld.wordpress.com/2011/02/