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Advanced Friction Ridge Development > Exam > Flashcards

Exam Flashcards

1
Q

Porous Processing Sequence

A

Visual examination
Indanedione
DFO
Ninhydrin
(Oil Red O if wetted)
Physical developer

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2
Q

Porous Surfaces

A

Absorbent, permeable to gases or liquids, water will be absorbed

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3
Q

Examples of porous surfaces

A

Paper, cardboard, unfinished woods

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4
Q

Non-Porous Surfaces

A

Non-absorbent, not permeable to liquid or gas, water will pour off

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5
Q

Examples of non-porous surfaces

A

Glass, plastic, metal

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6
Q

What kind of chemicals need to be used to examine porous surfaces?

A

Chemicals that react to amino acids or chemicals that are sensitive to lipids and oils from fingerprint residues

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7
Q

Amino Acid

A

Organic compounds that combine to form proteins

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8
Q

Urea

A

An organic compound essential for waste production by the body after metabolizing protein

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9
Q

Sodium Chloride

A

Natural occurring salt in the body

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10
Q

Lipids

A

Organic compounds not soluble in water but soluble in fat solvents such as alcohol. Energy reserves that are also important components of cell membranes.

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11
Q

Drying Fingerprints

A

Most of the print is water, which evaporates and leaves lipids, amino acids, sodium chloride, and urea

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12
Q

Amino Acids on Porous Surfaces

A

Bind to fibres, making them stable even when deepened

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13
Q

What kind of chemical treatments react to amino acids?

A

Most of them

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14
Q

What are the factors affecting how deep a latent print will penetrate a porous surface?

A

Environmental conditions such as moisture/humidity, and the porosity of the surface

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15
Q

How are aqueous fingerprint reagents applied?

A

Dipping, spraying, or brushing

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16
Q

What does the choice of reagent depend on?

A

Colour, has the substrate ever been wet, porosity of the substrate

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17
Q

What happens with latent prints on non-porous surfaces?

A

Latent print resides on the surface

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18
Q

Semi-Porous Surfaces

A

Allow certain liquids or gases through, usually by diffusion

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19
Q

Examples of semi-porous surfaces

A

Magazines, waxy-coated paper products, carbon paper, photographs, glossy wall paints, wallpapers, latex gloves, varnished woods

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20
Q

Destruction of exposed prints on non-porous surfaces

A

Easily destroyed by rubbing when places in plastic bags, so use paper. Fragile against the environmental conditions.

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21
Q

Benefits of Indanedione

A

Reacts with different amino acids than ninhydrin and develops more latent prints than ninhydrin or DFO alone. Fingermarks are both visible and fluorescent, and more fluorescent than using DFO.

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22
Q

Indanedione Signature

A

Light pink colour under ambient light

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23
Q

Disadvantage of Indanedione

A

May be possible to degrade/destroy DNA so must test for DNA prior to using

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24
Q

Zinc Salts in Indanedione

A

Enhances colour and luminescence, with the only drawback being a reduced shelf life

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25
Q

Application of Indanedione

A

Liquid is applied to substrate and allowed to dry. Heat press at 165°C for 10 seconds, or incubated at 100°C for 20 mins at 60-80% humidity.

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26
Q

DFO

A

Amino acid-sensitive reagent best viewed with ALS

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27
Q

Benefits of DFO

A

Highly fluorescent, develops twice as many prints as ninhydrin

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28
Q

DFO Signature

A

Pale purple colour

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29
Q

Application of DFO

A

Liquid is applied to substrate. Heat in incubator at 100°C for 20 mins.

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30
Q

Disadvantages of DFO

A

Must be completed in a dry environment

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31
Q

Ninhydrin

A

Water and alcohol soluble. Reacts with proteins and non-specific amino acids, proteins, and peptides

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32
Q

Ninhydrin Signature

A

Ruhemann’s purple colour

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33
Q

Application of Ninhydrin

A

Apply liquid to substrate. Moisture and heat in ninhydrin cabinet.

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34
Q

Disadvantages of Ninhydrin

A

Requires a carrier solution or polar solvent

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35
Q

Benefits of Ninhydrin

A

Works well on older latent prints

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36
Q

What if you have multiple items from the same scene that need to be examined the same way?

A

They can be treated as a group (can all go in the cabinet together), but must be examined individually

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37
Q

Sequential Processing

A

A process used to examine an item in a methodical and systematic approach

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38
Q

First 3 steps of sequential processing

A

Same in each examination. Visual examination in ambient light, then white light, then a forensic light source.

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39
Q

What’s wrong with terms like “decision” and “likelihood”?

A

Uncertainty

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40
Q

Identification according to CanFRWG

A

Identification is the opinion by the examiner, based on training, knowledge, and experience, that the friction ridge impression originated from the same source

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41
Q

“Uniqueness”

A

Misleading or confusing in court

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42
Q

What should you say instead of “sufficient uniqueness to individualize”?

A

“Friction ridge identification is established through the agreement of sufficient friction ridge formations in sequence”

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43
Q

Filters

A

Can be used to enhance an image or eliminate other areas of the image. Allows specific wavelengths to be recorded.

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44
Q

2 Common Filters

A

Barrier filter and bypass filter

45
Q

Barrier Filter

A

Suppress/block/absorb certain wavelengths and permit certain ones to help eliminate backgrounds. Blocks reflected light and transmits fluorescent light.

46
Q

Bypass Filter

A

Allows a limited range of wavelengths to be recorded and blocks all other colour. Used with UV to allow only the UV range of wavelength.

47
Q

Electromagnetic Radiation (ER) / Electromagnetic Spectrum

A

Energy moving in a wave-like motion. Includes x-rays, UV radiation, visible light, IR radiation, thermal radiation, radio waves, and microwaves.

48
Q

Red ER

A

700 nm, lower frequency, less energy

49
Q

Blue ER

A

400 nm, higher frequency, more energy

50
Q

3 Primary Characteristics of Light

A

Wavelength, frequency, speed

51
Q

How fast does ER travel in a vacuum?

A

Speed of light (299,792,458 m/s)

52
Q

Short Wavelength

A

High frequency, towards UV

53
Q

Long Wavelength

A

Low frequency, towards IR

54
Q

How are wavelengths measured?

A

Nanometres (nm)

55
Q

Visible Light Range

A

400-700 nm

56
Q

Near UV Range

A

300-400 nm

57
Q

Near IR Range

A

700-1100 nm

58
Q

What happens to ER when contacting a surface?

A

Reflected, absorbed, transmitted

59
Q

Types of Reflected Light

A

Specular or diffused

60
Q

Specular Reflected Light

A

Light strikes a smooth surface and reflects at the same angle and parallel

61
Q

Diffused Reflected Light

A

Light strikes a rough/textured surface and is scattered and not parallel

62
Q

Absorbed Light

A

Converts to heat or luminescence

63
Q

Luminescence

A

Molecules or atoms are in an excited higher energy state

64
Q

2 Types of Luminescence

A

Fluorescence and phosphorescence

65
Q

Transmitted Light

A

When light passes through an object without getting reflected or absorbed

66
Q

What happens to light that is incident on a glass surface?

A

It will be reflects at an angle equal to the angle of incidence and transmitted according to Snell’s Law. ~4% is reflected determined by the refractive index of glass. May cause light to change speed and direction.

67
Q

Refractive Index

A

Degree to which light bends. Frequency does not change but wavelength does.

68
Q

What is the basis of light filtration?

A

Refractive index

69
Q

Stokes Shift

A

Fluorescing light has a longer wavelength than incident radiation

70
Q

How long does fluorescence emission last?

A

About 1 second after emitting radiation is discontinued

71
Q

How long does phosphorescence emission last?

A

Several seconds after emitting radiation is discontinued

72
Q

Incandescence

A

When light is emitted from an object that has been heated. Glows when it’s hot.

73
Q

Chemiluminescence

A

Chemical reaction to cause heat and make it glow

74
Q

Fluorescence

A

Emission of light caused by the absorption of radiant energy from an external source. Emission of light continues on if the stimulus continues.

75
Q

Phosphorescence

A

Emission of light caused by the absorption of radiant energy from an external source or stimulus. Emission of light continues after the stimulus has stopped.

76
Q

Barrier Filter Use

A

Used to block reflected light and transmit the fluorescent light. Coloured to a specific wavelength.

77
Q

What does LASER stand for?

A

Light Amplification by Stimulated Emission of Radiation

78
Q

LASER as a Fluorescent Light Source

A

Device that produces a coherent wavelength of light. Forensics uses coherent lasers.

79
Q

LASER Wavelength

A

Works on a single wavelength between 525-550 nm, usually monochromatic 532 nm for fingerprint development in forensic labs

80
Q

What does LED stand for?

A

Light-Emitting Diode

81
Q

Use of LED-Based Light Sources

A

Intense light source, limited wavelengths for forensic use, fixed/non-tuneable wavelength, laser and ALS complement each other

82
Q

How are ninhydrin prints enhanced?

A

With metal salt treatments. Silver nitrate turns prints orange. Cadmium nitrate turns prints red.

83
Q

Analog

A

Chemical compound structurally similar to another but differs slightly in composition. Like the original with a light difference in atomically structure.

84
Q

Ninhydrin Analogues

A

MN and MTN. Both are amino acid-specific reagents that are structurally like ninhydrin but with improved capabilities. Both luminesce and are visible without a light source. Cheaper to produce but not as accepted.

85
Q

Physical Developer (PD)

A

Used when porous substrates have been wetted. Reacts to water-soluble sebaceous components of latent print residue.

86
Q

PD Signature

A

Dark grey to black due to the silver metal along the latent print ridges

87
Q

Benefits of PD

A

Can develop very old fingerprints. Can be used on wet/wetted items. Improves quality of fingermarks after DFO and ninhydrin.

88
Q

Disadvantages of PD

A

Long and time consuming, acidity weakens paper, silver may deposit in marks/creases/indentations/scratches, short shelf life, permanently stains any surface

89
Q

Oil Red O (ORO)

A

Lipophilic stain for developing prints on porous surfaces that have been wet. Better development than PD on some types of paper.

90
Q

ORO Application

A

3 step process involving coloration, neutralization, and drying

91
Q

ORO Signature

A

Red ridges against a pink background

92
Q

Nile Red (NR)

A

Lipophilic stain seen with 555 nm barrier filter. Excellent results on heavily sebaceous fingermarks.

93
Q

Disadvantages of NR

A

Expensive and dangerous. Nile blue is cheaper and safer.

94
Q

Small Particle Reagent (SPR)

A

To treat nonporous surfaces exposed to or immersed in water (even over 30 days). Fine particles of powder mixed with a surfactant. Reacts with fatty residue of latent prints.

95
Q

Surfactant of SPR Compositions

A

A weak detergent solution/surface agent. Key ingredient. Keeps fine particles suspended and evenly spreads the powder over a wet surface. Concentration can affect the quality of prints (higher concentration=weaker prints).

96
Q

Which SPRs are used on which surfaces?

A

Black charcoal powder or molybdenum disulphide for grey prints on light surfaces. Titanium dioxide or zinc carbonate for white prints on dark surfaces.

97
Q

Fingermark detection on fabric substrates

A

Ridge detail only possible with very fine weave patterns. Always test with similar fabrics first.

98
Q

100% Cotton

A

Behaves as a porous surface. Amino acid reagents, indanedione, ninhydrin, and gel lifters.

99
Q

Synthetic fabrics (like polyester and nylon)

A

Treat like non-porous. CA fuming followed by dye stain.

100
Q

Adhesive Substrates

A

Process non-porous (CA), then adhesive side powder suspension, then CA dye stain.

101
Q

Metallic Substrates

A

CA fuming with Rhodamine G6.

102
Q

Fingerprints on Guns and Ammunition

A

Low success rate. Can only be developed on exterior, magazine, and cartridge/cartridge case. Perspiration is acidic and may cause latent prints to be visibly etched into the cartridge surface without development. CA fuming and then dye staining.

103
Q

What affects recovery of fingerprints on guns and ammunition?

A

Heat from firing, ejection friction, falling on ground, fingerprint resistant coating on guns, textured surfaces for grip.

104
Q

Amido Black

A

Stains the protein in blood fingerprints a bluish-black colour. Methanol based formula for nonporous. Ethanol formula for porous and non porous but lighter prints but cheaper and safer.

105
Q

Acid Violet 17

A

Protein dye stain for porous items. Sprayed or dipped, stained, and then rinsed with water. Similar to amino black.

106
Q

Disadvantages of Amido Black and Acid Violet 17

A

Purple and black/blue colours not easily seen on dark background

107
Q

Acid Yellow 7

A

Used for bloody fingerprints and footprints on nonporous substrates. Fluoresces yellow-green under blue-green light. More effective on faint impressions but can be used on dark or patterned substrates.

108
Q

Thick Powder Suspensions

A

“Sticky-side powder”. Black powder in a detergent solution. Must be brushed on (bc she thiccc), left for a short time, and then rinsed with water.

109
Q

Benefits of Thick Powder Suspensions

A

Very effective on adhesive surfaces. Can be reapplied if weak prints are developed. White powder suspension will show prints on both sides of dark coloured tape.

Advanced Friction Ridge Development (4 decks)

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