Presentation on theme: "Fingerprints. Chapter 4 Fingerprints 2 Kendall/Hunt Publishing Company 2 Fundamental Principles of Fingerprints A fingerprint is an individual characteristic."— Presentation transcript:
Chapter 4 Fingerprints 2 Kendall/Hunt Publishing Company 2 Fundamental Principles of Fingerprints A fingerprint is an individual characteristic. A fingerprint remains unchanged during an individual’s lifetime. Fingerprints have general characteristic ridge patterns that permit them to be systematically classified.
Chapter 4 Fingerprints 3 All fingers, toes, feet, and palms are covered in small ridges. These ridges are arranged in connected units called dermal, or friction, ridges. These ridges help us get or keep our grip on objects. Natural secretions plus dirt on these surfaces leave behind an impression (a print) on those objects with which we come in contact. Kendall/Hunt Publishing Company 3
Chapter 4 Fingerprints 4 There are 3 main fingerprint patterns found in the human population: Loops: found in 60% of the population Whorls: found in 30% of the population Arches: found in 10% of the population A typical loop must have one or more ridges that enter from one side, loop, and then exit from the same side. Kendall/Hunt Publishing Company 4
Chapter 4 Fingerprints 5 October 4, 2011: Activity – page 77 # 1 Look at your fingerprints under the magnifying glass. Draw each of your prints in the boxes on the worksheet. Figure out whether they have arches, whirls, or loops. Kendall/Hunt Publishing Company 5
Chapter 4 Fingerprints 6 Fingerprint Analysis – page 77 - # 2 Inkprint all of your fingerprints Students work in groups of four: Compare your fingerprints to the other people in your group 1. What were some similarities in your group? 2. What were some differences in your group? 3. What are some problems you can foresee when using fingerprints to identify people? 4. What are some questions you have that you want answered by the end of this unit? Kendall/Hunt Publishing Company 6
Chapter 4 Fingerprints 7 Kendall/Hunt Publishing Company 7 AFIS The Automated Fingerprint Identification System—a computer system for storing and retrieving fingerprints Established in the 1970s IAFIS—the FBI’s Integrated Automated Fingerprint Identification System, which is a national database of all 10-print cards from all over the country
Chapter 4 Fingerprints 9 Kendall/Hunt Publishing Company 9 LOOPWHORLARCH
Chapter 4 Fingerprints 10 Kendall/Hunt Publishing Company 10 Arch An arch has friction ridges that enter on one side of the finger and cross to the other side while rising upward in the middle. They do NOT have type lines, deltas, or cores. Types Plain Tented
Chapter 4 Fingerprints 11 Kendall/Hunt Publishing Company 11 Loop A loop must have one or more ridges entering and exiting from the same side. Loops must have one delta. A double loop is made of two loops. Types Radial—opens toward the thumb Ulnar—opens toward the “pinky” (little finger)
Chapter 4 Fingerprints 12 Kendall/Hunt Publishing Company 12 Whorl A plain or central pocket whorl has at least one ridge that makes a complete circuit. An accidental is a pattern not covered by other categories. Whorls have at least two deltas and a core. Types Plain Central pocket Double loop Accidental
Chapter 4 Fingerprints 13 Kendall/Hunt Publishing Company 13 Primary Classification The Henry-FBI Classification System Each finger is given a point value. right left
Chapter 4 Fingerprints 14 Kendall/Hunt Publishing Company 14 Primary Classification, continued Assign the number of points for each finger that has a whorl and substitute into the equation: rightrightleftleftleft indexringthumbmiddlelittle+ 1 rightrightrightleftleft thumbmiddlelittleindexring+ 1 That total number is your primary classification number. =
Chapter 4 Fingerprints 15 Kendall/Hunt Publishing Company 15 Comparison There are no legal requirements in the United States on the number of points required for a match. Generally, criminal courts will accept 8 to 12 points of similarity.
Chapter 4 Fingerprints 16 Kendall/Hunt Publishing Company 16 Latent Prints Latent fingerprints are those that are not visible to the naked eye. These prints consist of the natural secretions of human skin and require development for them to become visible.
Chapter 4 Fingerprints 17 Kendall/Hunt Publishing Company 17 Developing Latent Prints Developing a print requires substances that interact with secretions, causing the print to stand out against its background. It may be necessary to attempt more than one technique, done in a particular order so as not to destroy the print. Powders—adhere to both water and fatty deposits. Choose a color to contrast with the background. Iodine—fumes react with oils and fats to produce a temporary yellow-brown color. Ninhydrin—reacts with amino acids to produce a purple color.
Chapter 4 Fingerprints 19 Kendall/Hunt Publishing Company 19 Other Prints Lips—several common patterns Voice—electronic pulses measured on a spectrograph Foot—size of foot and toes; friction ridges on the foot Shoes—can be compared and identified by type of shoe, brand, size, year of purchase, and wear pattern
Chapter 4 Fingerprints 20 Kendall/Hunt Publishing Company 20 Other Prints, continued Palm—friction ridges can be identified and may be used against suspects
Chapter 4 Fingerprints 21 Kendall/Hunt Publishing Company 21 Other Prints, continued Footprints are taken at birth as a means of identification of infants.
Chapter 4 Fingerprints 22 Kendall/Hunt Publishing Company 22 Other Prints, continued A man has been convicted of suffocating an eldery woman on the basis of earprint evidence. The assailant was caught after police matched the inprint of his ear on the victim’s window. Police believe that the thief put his ear to the window to listen for signs of anyone home. Earprint catches murderer
Chapter 4 Fingerprints 23 Kendall/Hunt Publishing Company 23 Other Prints, continued Teeth —bite marks are unique and can be used to identify suspects. These imprints were placed in gum and could be matched to crime scene evidence.