Fingerprinting Exam 1 Review
Fingerprinting Exam 1 Review FSC 340
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This 4 page Study Guide was uploaded by Chelsey Smith on Sunday October 2, 2016. The Study Guide belongs to FSC 340 at University of Southern Mississippi taught by Dr. Dean Bertram in Fall 2016. Since its upload, it has received 49 views. For similar materials see Fingerprinting in Forensic Science at University of Southern Mississippi.
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Date Created: 10/02/16
FSC 340- Fingerprinting Exam 1 Review Fingerprints- patterns of intricate design consisting of friction skin ridges found on the palmar side of fingers and thumbs Friction Skin Ridges- raised portion of skin consisting of veins, capillaries, and sweat glands Known prints- print that the person has already been identified- rolled with ink or live scan Unknown print- full or partial prints found at crime scenes- latent, visible latent, and plastic prints 3 Types of Patterns, Subcategories, and their Prevalence Loops- most common in about 60% of the population o Radial Loop- ridge flow moves towards the radius bone (closer to the thumb) o Ulnar Loop- ridge flow moves towards the ulnar bone (closer to the little finger) Arches- least common with only about 5% of the population o Plain Arch- lines are not parallel and follows a smooth up and over motion o Tented Arch-lines are not parallel and follow a more drastic up and over motion- there are 3 types of tented arches Whorls- 35% of population’s pattern o Central Pocket Whorl- circle pattern is centralized and confined to one small area o Plain Whorl- large circular pattern o Double Loop Whorl- “yin-yang” pattern- a big circular pattern consisting of two loops o Accidental Whorl- catch all category that consists of multiple patterns Fingerprint Numerical Classification Right thumb- 1 Left thumb- 6 Left pointer finger- 7 Right pointer finger- 2 Left middle finger- 8 Right middle finger- 3 Left ring finger-9 Left little finger- 10 Right ring finger- 4 Right little finger-5 3 Basic Requirements for a Loop There must be a sufficient recurve One delta only There must be at least a ridge count of 1 and to have this the count must cross at least one looping type ridge Sufficient Recurve Consists of the space between the shoulders of a loop, free of any appendages which abut it at a right angle outside of the recurve The innermost sufficient recurve is needed Shoulders of the loop are where the recurving ridges definitely turn inwards/curves An appendage is an attachment of a connection Appendages striking the outside of a recurve at a right angle will spoil the recurve, meaning there is no loop and the analyzer moves to the next innermost loop outside of the previously inspected non-loop o To Test for Appendages If you can smoothly trace the appendage along the loop, it’s good If there is a dot on top of the sufficient recurve in question, it’s still good (dot being defined as no taller than it is wide) An appendage may form a new loop Typelines Typelines- are the two innermost ridges which start or go parallel, diverge, and surround the pattern area Typelines are used to help find deltas- they are generally found on the opposite side of ridge flow There are not always two continuous ridges. When there is a definite break in a typeline, the ridge immediately outside of it is considered as a continuation (tends to surround pattern line) First check for the sufficient recurve Bifurcation- cannon be a typeline- resembles a Y Divergence- can stem from bifurcations to become typelines The arms of the bifurcation on which the delta is located can never be used for typelines Angles can never be used for typelines. They are formed by an abutting of one ridge against another Delta Delta- that point on a ridge at or the nearest to the point of divergence of two typelines, and located at or directly in front of the point of divergence A delta MUST be located on a friction skin ridge Deltas can be placed on o Dot o Bifurcation o Recurving of Ridges o Meeting of Two Ridges o Short Ridge o Ending Ridge Rules: o If you have more than one bifurcation, pick the one closest to the core (not at or in front of) o Bifurcation takes preference over any other choice (dot, recurving ridge, etc.) o Deltas may not be located in the middle of a ridge running between typelines towards the core, but placed at the end nearest to the core o A dot may be used as a delta- it has no direction o The delta may not be located at a bifurcation which does not open towards the core Core Core- the approximate center of the pattern Rules: o The core can be located on the shoulders of the innermost sufficient recurve farthest from the delta o The core can also be located on a spike/rod in the center of the innermost recurve, provided the spike/rod rises as high as the shoulders The centralized spike/rod takes preference over shoulder o If there is an even number of spikes/rods as high as the shoulders, then is located at the end of the farthest of the innermost spikes/rods from the delta Ridge Counting Only count the ridges between the delta and the core One ridge must be a looping ridge The delta and the core are not counted Fragments and dots are counted as ridges only if they appear as thick as surrounding ridges Count the arms of a bifurcation twice If the delta is on the only loop, there is no ridge count (goes back to requirements for loops) White space must intervene between delta and first ridge count If the delta is above the shoulders of a single looping type ridge, and the core is on the shoulder, there is no ridges count unless the imaginary line cuts the recurve Natural and unnatural breaks in ridges are to be distinguished by the judgement of the individual classifier
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