Published on September 7, 2009
Slide 1: Forensic Science Fingerprints T. Trimpe 2006 http://sciencespot.net Fingerprint Principles : Fingerprint Principles According to criminal investigators, fingerprints follow 3 fundamental principles: A fingerprint is an individual characteristic; no two people have been found with the exact same fingerprint pattern. A fingerprint pattern will remain unchanged for the life of an individual; however, the print itself may change due to permanent scars and skin diseases. Fingerprints have general characteristic ridge patterns that allow them to be systematically identified. Fingerprint Classes : Fingerprint Classes There are 3 specific classes for all fingerprints based upon their visual pattern: arches, loops, and whorls. Each group is divided into smaller groups as seen in the lists below. Interesting Info : Interesting Info Did you know? Dactyloscopy is the study of fingerprint identification. Police investigators are experts in collecting “dactylograms”, otherwise known as fingerprints. Fingerprint Factoid: 60% of people have loops, 35% have whorls, and 5% have arches Arches : Arches Arches are the simplest type of fingerprints that are formed by ridges that enter on one side of the print and exit on the other. No deltas are present. Loops : Loops Loops must have one delta and one or more ridges that enter and leave on the same side. These patterns are named for their positions related to the radius and ulna bones. NOTE: On the left hand, a loop that opens to the left would be an ulnar loop, while one that opens to the right would be a radial loop. Whorls : Whorls Whorls have at least one ridge that makes (or tends to make) a complete circuit. They also have at least two deltas. If a print has more than two deltas, it is most likely an accidental. Draw a line between the two deltas in the plain and central pocket whorls. If some of the curved ridges touch the line, it is a plain whorl. If none of the center core touches the line, it is a central pocket whorl. Plain Whorl Central Pocket Whorl Whorls – Part 2 : Whorls – Part 2 Identify each fingerprint pattern. : Identify each fingerprint pattern. ? A B C D E Right Hand Left Hand Left Hand Right Hand Right Hand Other Systems of Identification : Other Systems of Identification DNA- can be extracted from saliva, blood, semen, or hair Dental Records Handwriting Voice Analysis Note: None of these are as conclusive as fingerprints!!! Fingerprinting in Animals : Fingerprinting in Animals Koala Bears have prints strikingly similar to humans Horses are identified by their snout Whales are identified by their fluke Fingerprint Files : Fingerprint Files The Department of Justice began a fingerprint file in the early 1900’s The FBI began a fingerprint file in 1930, which is now considered to be the largest collection of fingerprints in the world Removing Fingerprints From the Crime Scene : Removing Fingerprints From the Crime Scene Most commonly, latent prints are recovered from the scene of a crime Latent prints are prints left by the oils in your skin that are invisible to the unaided eye They need to be lifted in order to be visualized Types of Prints : Types of Prints Visible Prints: These are found when the finger deposits a visible material such as ink, dirt, or blood onto a surface Plastic Prints: This occurs when a fingerprint in impressed into a soft surface such as clay, soap, wax, or dust. Latent Prints: These prints are usually invisible to the unaided eye and are caused by depositing oil on surfaces that are touched Lifting Latent Prints : Lifting Latent Prints Absorbent Surfaces These prints need to be fumed using superglue, iodine, or physical developer The chemicals react with the oils in the skin when heated in a chamber to visualize the print Examples of surfaces that are fumed: clothing, paper Non Absorbent Surfaces These prints can be dusted with powder and a brush and lifted with tape Examples of surfaces that are dusted: wood (table, chairs), glass (windows, tableware), plastic, metal (shotgun, knife, doorknob) A closer look at fuming : A closer look at fuming Formation of Fingerprints : Formation of Fingerprints Fingerprints are formed before birth, during the development of the hands. Fingerprints aren't actually formed in the skin, but are caused by ridges in the flesh underneath the skin. Genetics plays some part in their formation, but even identical twins (who have identical DNA) have different fingerprints. Fingerprints are formed on an fetus at about 5 months into the gestation. Can a person change or remove their fingerprints? : Can a person change or remove their fingerprints? YES Very difficult to remove all ridge characteristics You would have to remove 5 of the 7 layers of the epidermis to damage the fingerprint pattern People have tried burning in acid, using metal files, skin grafting NO Nearly impossible to remove them entirely Even burning in corrosive acid can still leave fingerprint patterns undamaged in spots To identify a print police need to match at least 12 minutae points. Slide 19: Avoid Partial Prints GOOD PRINTGet as much of the top part of your finger as possible! Directions : Directions 1st – Roll the “pad” portion of your thumb over the ink pad from the left side of your thumb to the right. You do not have to push down really hard! 2nd – Roll the “pad” portion of your thumb from the left side of your thumb to the right in the correct box on your paper to make a thumbprint. 3rd – Continue this process to make a fingerprint of all ten fingers on the “My Prints” worksheet. 4th –Use your notes and a magnifying lens to help you figure out what type of pattern is found in each of your fingerprints. Label each one with the pattern’s name.