Lecture 10: Physical Evidence IV (Fingerprints) Flashcards

1
Q

What are the three layers of skin in vertebrate animals?

A

Epidermis, Dermis, Hypodermis

The hypodermis is often not mentioned in basic discussions of skin layers.

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2
Q

What are the two assumptions regarding fingerprints for personal identification?

A
  1. The fingerprints of an individual stay unchanged throughout life
  2. No two fingerprints are identical.
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3
Q

Why do we have fingerprints?

A
  • More friction -> better grip
  • Prevent skin from tearing early
  • Improve sense of touch
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4
Q

What are the three main classifications of fingerprints?

A
  1. Arch
  2. Loop (most common 65%)
  3. Whorl
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5
Q

What is a core?

A

Center of a loop or whorl

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6
Q

What is a delta?

A

A triangle ridge pattern

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7
Q

What type of fingerprint pattern has no deltas?

A

Arches.

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8
Q

What is a characteristic feature of tented arches in fingerprints?

A

They have a spike in the center.

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9
Q

Describe the features of loops

A
  • One delta
  • One or more ridge that leave on the same side
  • Named according to position relating to radius and ulna
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10
Q

Describe the features of whorl

A
  • Two or more delta
  • One or more ridge (forms complete circuit)
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11
Q

What are the four subtypes of whorls in fingerprint classification?

A
  1. Plain whorl
  2. Central pocket whorl
  3. Double loop whorl
  4. Accidental whorl.
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12
Q

How to differentiate between plain whorl and central pocket whorl?

A
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13
Q

What is the primary characteristic of double loop whorls?

A

Made up of any two loops combined into one print.

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14
Q

What are the three main categories of fingerprints?

A
  1. Visible/patent
  2. Plastic
  3. Latent
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15
Q

What are visible fingerprints?

A
  • Visible by naked eye
  • when an appropriate substance is transferred by the fingertips onto a suitable surface
  • e.g. inks, blood
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16
Q

What are plastic fingerprints?

A

Fingerprints pressed into a suitably soft material such as putty or clay.

17
Q

How are latent fingerprints different from visible and plastic fingerprints?

A

Cannot be seen with the naked eye

18
Q

What is the composition of latent fingerprints?

A

Perspiration exuded from sweat pores, containing 95% water and 5% other substances including salts and amino acids/ body oil and grease

19
Q

Name the 7 methods for development of latent fingerprints

A

• Fluorescence examination
• Superglue fuming
• Iodine fuming
• Powders
• Acid dyes
• Ninhydrin and/or DFO application
• Gentian violet

20
Q

What technique is used for developing latent fingerprints on non-porous surfaces (e.g. rubber/metal)?

A
  • Superglue fuming (ethyl cyanoacrylate)
  • Apply before applying powders/dye stains
  • Cyanoacrylate vapors adhere to amino acids left behind by fingerprint secretions
21
Q

What substance is used for porous surfaces (e.g. paper) for latent fingerprint development?

A
  • Ninhydrin
  • Reacts with amino acid to give bluish-purple color
  • spray with ZnCl2 for fluorescence
22
Q

What is the oldest technique to develop latent fingerprints?

A
  • Ioding fuming
  • On any surface
  • Heat iodine solid and undergo sublimation
  • fingerprint reacts with iodine vapor to form yellow-brown print
23
Q

What is a common visualization technique for fingerprints on hard surfaces?

A
  • Powders
  • Adheres to grease or dirt
  • For hard, relatively smooth, non-porous surfaces
24
Q

How do acid dyes develop latent fingerprints?

A
  • For fingerprints contaminated with blood
  • Stains proteins present in blood e.g. RBC
  • e.g. acid black 1, acid violet 17, acid yellow 7
25
Q

What is the role of acid dyes in fingerprint analysis?

A

To develop fingerprints contaminated with blood.

26
Q

What is the method used to visualize latent fingerprints with fluorescence?

A
  • Fluorescence examination
  • lasers or high-intensity light sources
  • due to contaminants (grease)
  • or chemical treatment (ZnCl2 + ninhydrin)
27
Q

What is the technique used for developing fingerprints on adhesive surfaces?

A
  • Gentian Violet (purple dye)
  • On adhesive surface of sticky tape except Sellotape
  • Stains fatty components of sweat
28
Q

What is the purpose of the ACE-V method in fingerprint analysis?

A

A standard method for fingerprint examiners:
Analysis
Comparison
Evaluation
Verification

29
Q

What does IAFIS stand for?

A

Integrated Automated Fingerprint Identification System.

30
Q

Describe how the IAFIS works

A
  • Computerized program
  • Databank with fingerprints of over 47M ppl
  • Searches a set of ten fingerprints at 500,000 in less than a second
  • Uses algorithms or formulas to assign each possible match a score
  • Takes about 2 hours to find possible matches
31
Q

What is the average number of minutiae found on a fingerprint?

A

Approximately 150.

32
Q

Fill in the blank: Fingerprint identification requires a minimum of _______ points to be considered a match.

33
Q

True or False: Fingerprints can be permanently erased.

A

False.

Only temporarily; they will grow back if removed with chemicals

34
Q

True or False: Fingerprint identification is completely error-proof.

35
Q

What famous criminal case involved fingerprint evidence linking to the assassination of Dr. Martin Luther King?

A

James Earl Ray.

36
Q

What is the outcome of the Brandon Mayfield case regarding fingerprint misidentification?

A

He was falsely accused due to misidentified fingerprints.