Lab 7 Fingerprint-1

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The University of Tennessee, Knoxville *

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105

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Anthropology

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Oct 30, 2023

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Dermal Ridge Pattern and Latent Prints Lab Page 1 ANTH 105 Dermal Ridge Patterns and Latent Prints Lab Anthropologists know that in addition to the forensic practice of comparing questioned prints against known ones, ridge patterns are reflective of population patterns. We will begin with an overview of the basics of dermatoglyphics and advance to how CSIs recover prints. In this lab we will practice creating a series of known reference prints (of you) and also how to render latent prints. Thoroughly review the information contained in this lab before continuing. Dermal ridges result from convoluted layers of epidermal cells; becoming visible at three months they are complete by the sixth month in utero. Individual qualities are attributable to numerous effects including nerve growth, patterning or distribution of sweat glands, and epithelial growth. Also as growth is a dynamic process, and many components contribute and mutually interact, we can further appreciate the potential for individual variation. Studies of fingerprint patterns in related individuals indicate that approximately 90% of the pattern is inherited (Brues, 1990). Terminology. See on Figure at right. Ridge: raised line that is part of the visible print. Furrow: low spaces not captured between ridges. Core: innermost ridge of the pattern, at approximate center. Delta/triradius: point where 3 ridges diverge or point nearest center of divergence of type lines. Type line: innermost ridge that surrounds pattern area. Ridge count: number of ridges transect line drawn from core to delta. TRC: sum of total count of ridges on all fingers. Ridge patterns are grouped into three primary categories. See images in Figure below • Arches: ridges cross smoothly or up thrust at center. No ridge count scores. • Loops: ridges rise, curve and return; have a single delta and hence a single line for ridge count o ulnar loops : loops open and flow toward ulna—forearm bone on pinky side as view palm o radial loops: opposite of above; open to radius—bone on thumb side as you view palm • Whorls: ridges form concentric circles, whirlpools or spirals; 2 deltas therefore 2 lines for ridge counts Arches Loops Whorls Review the images above and consult cards that were distributed. Look closely at several of your fingers. Can you see any of your patterns? Also appreciate the numerous variants of each simple type that exist. There are several parts to this lab. 1. Prepare a 10 print reference card (5 print only) of yourself 2. Make and collect two questioned prints 3. Compare the questioned against the knowns and make an evaluation.

Dermal Ridge Pattern and Latent Prints Lab Page 2 As with other evidence, practitioners engage in the comparison of K and Q items. The questioned prints are those discovered and collected at a scene. We recognize three types: patent, plastic, and latent. • A patent print is clearly visible and can easily be identified. • Plastic prints are impressions and have 3D qualities. • Latent prints are not visible and require a level of processing to be rendered visible and useful. Known prints are collected in a standardized system as presented below. We will engage in both of these in this lab. Remember that ACE-V was first presented for fingerprint assessments so ensure your reference prints are worthy of analysis so you can engage in a comparison of the Q and the K prints. Provide your evaluation. Realize that in reality questioned prints are submitted for electronic coding and comparison to databases for potential knowns, but the actual comparisons are done manually. In order these are the steps we will engage in during the lab session. 1. Using the two glass slides provided, make two latent prints using the non-dominant hand a. Rub your finger on your chin or nose before pressing to the slide 2. Collect knowns: prepare a 10 5 print reference card (5) of yourself non-dominant hand. 3. Collect two questioned: recover two latent prints a. Using true powder raise a print from a smooth, (painted), non-porous surface i. How might different colored powders be worthy of consideration? b. Using magnetic powder raise a print c. What should you never do if you put too much powder on the print area? Why? __________________________________________________________________ 4. Compare the questioned against the knowns and make an evaluation. Part 1: Make two latent prints on the provided glass slides. Touch some sebum and transfer it to the slides. Use two different fingers from your non-dominant hand Set these slides aside as you will process the latent prints in Part 3 of this lab Part 2: Prepare HALF (just one hand) of a standard 10 print reference card using the next page (Page 4). • Known Reference Prints (IN BLUE BOXES AT BOTTOM OF PAGE) Create your “5” print card. This is not an official item, but it lets us be cleaner! Select your non dominant hand and print each finger using the form on page 4. Note that it is not just the oval tip of the finger that is printed. Roll each finger to generate square prints like those in the card at right. Reflect on the Canvas video. Ideally use your non-dominant hand for the 5 print; but at least the same one as you did for the latent prints. Normally you do not print yourself. Stand up as you make your prints. Fold page 3 so that the row you are completing is on the edge of your workspace. Note how the top row is for the right hand and the middle row is for each finger of the left hand. We suggest you complete the row that is your non-dominant hand. Complete the half of the lower row that corresponds to the side of the body that you printed. Reflect on the process observed in the Canvas video link. If you make a mess and want to start over, shift into the row associated with the other side of the body and overwrite the side labels. IN THE RED BOXES identify the primary pattern found on each print (arch, loop (ulnar or radial), whorl).

Part 3: Process the two latent prints you made on the provided glass slides using physical methods. There are two primary physical methods of developing prints: True and magnetic powder. Be sure to use the correct brush! True powder is best on polished, smooth, nonporous surfaces. Magnetic powder is used on nonmagnetic surfaces and also on uneven, textured surfaces including plastics, leather dashboards, car sides. We will use both; one on each slide and tape lift them. No chemical methods will be practiced. You can do the following in either order: true then magnetic, or vice versa. • Latent print 1: Q1 Step 1 photograph the print. True powder dusting is one method you will use to develop one of your latent prints. Swirl the brush gently to ensure no residue powder adheres to it. Dip it lightly into the powder and then lightly apply it to the surface. Once the print begins to appear, then continue gently brushing with the direction of the ridges. Be careful not to brush away the print! Preserve the print in step 2. Step 2 make a tape lift of the print. CAREFULLY PLACE A SECTION OF TAPE OVER THE PRINT. THEN Remove the tape and place it onto half of an index card and then lightly tape the card on top of the picture with the green border on page 4. We will use this in part 4. • Latent print 2: Q2 Step 1 photograph the print. Magnetic powder dusting is one method you will use to develop one of your latent prints. The brush is different for magnetic powder. One end has a release on it and the other is a magnetic. The brush does not touch the print, just the magnetic particles. Bring the wand close to the magnetic particles so an amount attaches to it. Swirl the particles so they gently touch the area where the print is located. Put the wand over the canister of magnetic powder and release the remaining particles back into the jar. Preserve the print in step 2. Step 2 make a tape lift of the print. CAREFULLY PLACE A SECTION OF TAPE OVER THE PRINT. THEN Remove the tape and place it onto half of an index card and then lightly tape the card on top of the picture with the orange border on page 4. We will use this in part 4. Part 4: ACE-V You have two latent prints (orange and green boxes) and a set of known prints (blue box). While you may recall which finger you used to make each print, you need to engage in a side by side comparison and identify and list several points of comparison. Compare the green box print against the five print knowns, determine which K finger is the Q1 print. Do the same for the orange box tape lift: Q2. You can move the tape lifts and position next to the K prints as you work. • Comparison of Q1 Identify, label, and list (here) 5 points of comparison between green Q1 and the K print. List these and indicate the exact finger in the green box on page 4. 1. __________________________________ 4. ________________________________ 2. __________________________________ 5. ________________________________ 3. __________________________________ • Comparison of Q2 Identify, label, and list (here) 5 points of comparison between each Q2 and the K print. List these and note the exact finger in the orange box on page 4. 1. __________________________________ 4. ________________________________ 2. __________________________________ 5. ________________________________ 3. __________________________________

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