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FingerprintingChapter 15

Crystal Violet

Red Fluorescent

Inked

Courtesy of C. Fanning

Courtesy of C. Fanning

Courtesy of C. Fanning

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Prints

• Making printsRolling printsModus operandi

• Identifying printsRidge count3 types- loop, whorl, archMinutiae

• Lifting printsBlack, white, fluorescent powdersChemicals-ninhydrin, iodine, silver nitrate, cyanoacrylate

• Other types of prints

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It’s time to make some prints!

Avoid Partial Prints

GOOD PRINTGet as much of the top part of your finger as possible!

Directions for making a ‘10 card’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 – TIFO – Thumbs in, Fingers out. Roll the “pad” portion of your thumb 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.

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Prints

• Making printsRolling printsModus operandi

• Identifying prints3 types- loop, whorl, archRidge countMinutiae

• Lifting printsBlack, white, fluorescent powdersChemicals-ninhydrin, iodine, silver nitrate, cyanoacrylate

• Other types of prints

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• All fingerprints are divided into three classes on the basis of their general pattern: loops, arches, and whorls (L.A.W.).

• Loops are the most common type (65%)• Whorls (30%)• Arches (5%)

Classification

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• A loop must have one or more ridges entering from one side of the print, recurving, and exiting from the same side.

Ulnar loop Radial loop

• All loops must have one delta, which is the ridge point at or directly in front of the point where two ridge lines (type lines) diverge.

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• A plain whorl and a central pocket loop have at least one ridge that makes a complete circuit.

Whorls are divided into four groups: plain, central pocket loop, double loop, and accidental.

All whorl patterns have type lines and a minimum of two deltas.

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The double loop is made up of two loops combined into one fingerprint.

• An accidental either contains two or more patterns, or is a pattern not covered by the other categories.

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Core (center)

Delta (fork)

Classification: Ridge Count

Classification: Ridge Count

• # ridges between core and delta

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• Arches, the least common of the three general patterns, are divided into two distinct groups: plain arches and tented arches.

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• The plain arch is formed by ridges entering from one side of the print, rising and falling, and exiting on the opposite side (like a wave).

• The tented arch is similar to the plain arch except that instead of rising smoothly at the center, there is a sharp upthrust or spike, or the ridges meet at an angle that is less than 90 degrees.

• Arches do not have type lines, deltas, or cores.

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•Let’s Practice!!

• Eight basic pattern types are recognized by the FBI

•Ten basic details within the patterns (minutiae)

• Ideally 12 identical points for a match

Fingerprint Patterns

Minutiae patterns

Ridge Minutiae

Identify Minutiae