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Fingerprints Flashcards

1
Q

What are fingerprints used for in forensics?

A

Identification purposes:
* Criminal
* Legal (immigration, borders)
* Background checks
* Security (phones, iPads)
* Fraud prevention (cashing checks)

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2
Q

Fingerprints are ___ & ___

A
  • Highly discriminating (variable)
  • Persistent
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3
Q

How do we know fingerprints are persistent?

A

Herschell (1916)
* Took his own fingerprint over the span of 40 years and saw there was no change

Maceo (2011)
* Fingerprint sourcebook, chapter 2: delves into biology of how fingerprints are formed

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4
Q

What are two conditions that can influence fingerprints?

A

Dysplasia:
* Ridges not lining up and creating a proper pattern

Eczema:
* Dry skin that can change, leading to fingerprints not being persistent

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5
Q

Fingerprint terminology

A

Volar pad: Areas that are meatier in the hands
2-3 ridge patterns form at the same time
Ridges: form at around 10-16 weeks
Delta: where the different fingerprint patterns meet

Note: Identical twins share DNA but not fingerprints

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6
Q

What are the three types of prints?

A

Latent prints:
* Must be developed to be visualized (prints exist but we can’t see them until we develop them)
* These are “natural” prints

Patent prints:
* Prints that are already visible and no development to be visible
* Blood, paint, ink, dust, chocolate

Plastic print:
* Impressed into a malleable surface
* putty, clay, wax, tacky paint

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7
Q

What are the different deposition factors?

(Three factors)

A

Pre-transfer conditions:
* Condition or health of donor skin

Transfer conditions:
* Surface conditions
* Pressure

Post-transfer conditions:
* Environmental factors

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8
Q

What are the substrate types?

A

Porous:
* Absorb water-soluble deposits

Non-porous:
* Do not absorb any part of fingerprint deposit

Semi-porous:
* Absorb water-soluble deposits slowly over hours
* Waxed surfaces, varnished wood, glossy paper, some plastics, some paints

Adhesive
Textured surfaces

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9
Q

What are the fingerprint physical processing types?

(non-porous powder agents)

A
  • Black powder
  • White powder
  • Bi-chromatic (dark/light)
  • Magnetic powder
  • Fluorescent powder (dropping out backgrounds)
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10
Q

What are the fingerprint physical processing types?

(wet items)

A

Small particle reagent (SPR)
* Applied with spray bottle

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11
Q

What are the fingerprint physical processing types?

(Adhesives)

A

Sticky side powder (WetWop)
* Applied to any adhesive surface
* Liquid that’s brushed on

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12
Q

What are the fingerprint physical processing types?

(porous evidence)

A

Chemical processing:
* Ninhydrin (Ruhemann’s purple)

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13
Q

What are the fingerprint physical processing types?

(Chemical)

A

Cyanoacrylate Fuming (CA) (superglue)
* Works for non-porous evidence items because it makes fingerprints:
* Visible
* Permanent
* Essentially coats fingerprints with superglue and makes them indestructible
* Can follow up with powder or chemical dye stain if not overly visible

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14
Q

What is a blood physical processing type?

A

Amido Black:
* Reacts with blood proteins
* Enhances latent blood marks on non-porous surfaces
* May destroy blood presumptive tests

Note: Luminol washes fingerprints away

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15
Q

What are the preservation techniques for latent fingerprints?

(Four types)

A

Photography

Scanning
* Great for paper

Lifting
* Lift tape
* Hinge lifters
* Gelatin lifters

Casting
* Plastic impressions
* Textured surfaces, etc.

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16
Q

What are the ridge pattern types?

A
  • Arches
  • Tented arches
  • Right loops
  • Left loops
  • Plain whorl
  • Central poket loop (closed circle)
  • Double loop (2 loops circling)
  • Accidental whorl
17
Q

What are the three levels of details considered in fingerprints?

A

Level 1: Ridge flow
* Overall flow
* Pattern type

Level 2: Ridge path
* Minutiae

Level 3: Ridge shape
* Pores
* Edge shapes
* Thickness
* Angles

18
Q

What are the four steps of comparison for fingerprints?

A

Analysis:
Looking at scene print by itself
Comparison:
Looking at latent print vs exemplar
Evaluation:
Making the decision
Verification:
Open verification and blind verification

Hint: ACE-V

19
Q

What is AFIS?

A

Automated Fingerprint Identification System:
* Looks at fingerprint patterns and minutiae and compares them to other prints

20
Q

Who developed one of the fingerprint identification systems? Who adopted it?

A

Sir Edward Richard Henry
* Developed a search and filing system
* Adopted by Scotland Yard

21
Q

What is the digital fingerprint scanner called?

Forensic Science (7 decks)

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