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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
Application of Indanedione
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.
26
DFO
Amino acid-sensitive reagent best viewed with ALS
27
Benefits of DFO
Highly fluorescent, develops twice as many prints as ninhydrin
28
DFO Signature
Pale purple colour
29
Application of DFO
Liquid is applied to substrate. Heat in incubator at 100°C for 20 mins.
30
Disadvantages of DFO
Must be completed in a dry environment
31
Ninhydrin
Water and alcohol soluble. Reacts with proteins and non-specific amino acids, proteins, and peptides
32
Ninhydrin Signature
Ruhemann's purple colour
33
Application of Ninhydrin
Apply liquid to substrate. Moisture and heat in ninhydrin cabinet.
34
Disadvantages of Ninhydrin
Requires a carrier solution or polar solvent
35
Benefits of Ninhydrin
Works well on older latent prints
36
What if you have multiple items from the same scene that need to be examined the same way?
They can be treated as a group (can all go in the cabinet together), but must be examined individually
37
Sequential Processing
A process used to examine an item in a methodical and systematic approach
38
First 3 steps of sequential processing
Same in each examination. Visual examination in ambient light, then white light, then a forensic light source.
39
What's wrong with terms like "decision" and "likelihood"?
Uncertainty
40
Identification according to CanFRWG
Identification is the opinion by the examiner, based on training, knowledge, and experience, that the friction ridge impression originated from the same source
41
"Uniqueness"
Misleading or confusing in court
42
What should you say instead of "sufficient uniqueness to individualize"?
“Friction ridge identification is established through the agreement of sufficient friction ridge formations in sequence”
43
Filters
Can be used to enhance an image or eliminate other areas of the image. Allows specific wavelengths to be recorded.
44
2 Common Filters
Barrier filter and bypass filter
45
Barrier Filter
Suppress/block/absorb certain wavelengths and permit certain ones to help eliminate backgrounds. Blocks reflected light and transmits fluorescent light.
46
Bypass Filter
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
Electromagnetic Radiation (ER) / Electromagnetic Spectrum
Energy moving in a wave-like motion. Includes x-rays, UV radiation, visible light, IR radiation, thermal radiation, radio waves, and microwaves.
48
Red ER
700 nm, lower frequency, less energy
49
Blue ER
400 nm, higher frequency, more energy
50
3 Primary Characteristics of Light
Wavelength, frequency, speed
51
How fast does ER travel in a vacuum?
Speed of light (299,792,458 m/s)
52
Short Wavelength
High frequency, towards UV
53
Long Wavelength
Low frequency, towards IR
54
How are wavelengths measured?
Nanometres (nm)
55
Visible Light Range
400-700 nm
56
Near UV Range
300-400 nm
57
Near IR Range
700-1100 nm
58
What happens to ER when contacting a surface?
Reflected, absorbed, transmitted
59
Types of Reflected Light
Specular or diffused
60
Specular Reflected Light
Light strikes a smooth surface and reflects at the same angle and parallel
61
Diffused Reflected Light
Light strikes a rough/textured surface and is scattered and not parallel
62
Absorbed Light
Converts to heat or luminescence
63
Luminescence
Molecules or atoms are in an excited higher energy state
64
2 Types of Luminescence
Fluorescence and phosphorescence
65
Transmitted Light
When light passes through an object without getting reflected or absorbed
66
What happens to light that is incident on a glass surface?
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
Refractive Index
Degree to which light bends. Frequency does not change but wavelength does.
68
What is the basis of light filtration?
Refractive index
69
Stokes Shift
Fluorescing light has a longer wavelength than incident radiation
70
How long does fluorescence emission last?
About 1 second after emitting radiation is discontinued
71
How long does phosphorescence emission last?
Several seconds after emitting radiation is discontinued
72
Incandescence
When light is emitted from an object that has been heated. Glows when it's hot.
73
Chemiluminescence
Chemical reaction to cause heat and make it glow
74
Fluorescence
Emission of light caused by the absorption of radiant energy from an external source. Emission of light continues on if the stimulus continues.
75
Phosphorescence
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
Barrier Filter Use
Used to block reflected light and transmit the fluorescent light. Coloured to a specific wavelength.
77
What does LASER stand for?
Light Amplification by Stimulated Emission of Radiation
78
LASER as a Fluorescent Light Source
Device that produces a coherent wavelength of light. Forensics uses coherent lasers.
79
LASER Wavelength
Works on a single wavelength between 525-550 nm, usually monochromatic 532 nm for fingerprint development in forensic labs
80
What does LED stand for?
Light-Emitting Diode
81
Use of LED-Based Light Sources
Intense light source, limited wavelengths for forensic use, fixed/non-tuneable wavelength, laser and ALS complement each other
82
How are ninhydrin prints enhanced?
With metal salt treatments. Silver nitrate turns prints orange. Cadmium nitrate turns prints red.
83
Analog
Chemical compound structurally similar to another but differs slightly in composition. Like the original with a light difference in atomically structure.
84
Ninhydrin Analogues
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
Physical Developer (PD)
Used when porous substrates have been wetted. Reacts to water-soluble sebaceous components of latent print residue.
86
PD Signature
Dark grey to black due to the silver metal along the latent print ridges
87
Benefits of PD
Can develop very old fingerprints. Can be used on wet/wetted items. Improves quality of fingermarks after DFO and ninhydrin.
88
Disadvantages of PD
Long and time consuming, acidity weakens paper, silver may deposit in marks/creases/indentations/scratches, short shelf life, permanently stains any surface
89
Oil Red O (ORO)
Lipophilic stain for developing prints on porous surfaces that have been wet. Better development than PD on some types of paper.
90
ORO Application
3 step process involving coloration, neutralization, and drying
91
ORO Signature
Red ridges against a pink background
92
Nile Red (NR)
Lipophilic stain seen with 555 nm barrier filter. Excellent results on heavily sebaceous fingermarks.
93
Disadvantages of NR
Expensive and dangerous. Nile blue is cheaper and safer.
94
Small Particle Reagent (SPR)
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
Surfactant of SPR Compositions
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
Which SPRs are used on which surfaces?
Black charcoal powder or molybdenum disulphide for grey prints on light surfaces. Titanium dioxide or zinc carbonate for white prints on dark surfaces.
97
Fingermark detection on fabric substrates
Ridge detail only possible with very fine weave patterns. Always test with similar fabrics first.
98
100% Cotton
Behaves as a porous surface. Amino acid reagents, indanedione, ninhydrin, and gel lifters.
99
Synthetic fabrics (like polyester and nylon)
Treat like non-porous. CA fuming followed by dye stain.
100
Adhesive Substrates
Process non-porous (CA), then adhesive side powder suspension, then CA dye stain.
101
Metallic Substrates
CA fuming with Rhodamine G6.
102
Fingerprints on Guns and Ammunition
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
What affects recovery of fingerprints on guns and ammunition?
Heat from firing, ejection friction, falling on ground, fingerprint resistant coating on guns, textured surfaces for grip.
104
Amido Black
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
Acid Violet 17
Protein dye stain for porous items. Sprayed or dipped, stained, and then rinsed with water. Similar to amino black.
106
Disadvantages of Amido Black and Acid Violet 17
Purple and black/blue colours not easily seen on dark background
107
Acid Yellow 7
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
Thick Powder Suspensions
"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
Benefits of Thick Powder Suspensions
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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