CSI/QAC Exam 2

Is it possible to individualize a hair based on morphology alone?

No

What is the difference between class and individual characteristics?

Hair WITHOUT the follicle = provides class characteristics

Hair WITH the follicle = allows for DNA fingerprinting and provides individual characteristics

What are the 3 main layers of the hair shaft? Also, what is the follicle?

Medulla - center of the shaft

Cortex - middle section, contains pigment

Cuticle - outer layer, overlapping layers of cells to protect hair

Hair is produced in the follicle → Located in the dermis and opens up into the epidermis

What are identifiable characteristics of hair (i.e., cuticle patterns, Medullary index, Medulla continuity)?

Cuticle = Scales always point towards the tip of the hair. Scale pattern is useful in species identification.

The cortex has embedded pigment granules whose color, shape, and distribution differ

Medullary Index = measures the diameter of the medulla relative to the diameter of the hair shaft (fraction) (continuity below)

What is the follicle tag, and why is it important for our forensic analysis?

Follicular Tag - translucent tissue surrounding the hair’s shaft near the root (rich source of nuclear DNA)

How might isotope analysis from hair help us forensically (see isotope article)

Isotopes can determine a general locale for an individual and even determine diet

What is the drawback of performing morphological hair analysis?

• Tend to be subjective

• Highly dependent on the skills and integrity of the analyst

• Hairs can vary (each strand can be a bit different); thus, we need to collect more than a dozen reference samples

• FBI review found microscope matches to be incorrect 11% of the time

What part of the hair contains nuclear DNA (mtDNA?) and in what phase is the concentration of DNA the highest?

Nuclear DNA can be found in hair roots if present

Mitochondrial DNA can be found in the hair itself

What are the ways fibers are analyzed? (i.e., Color, cross-section, dye analysis, burn, acid, etc.)

Microscopic Analysis, Flame Test, Chemical Test, Chromatography Test, Density Test, UV Test, and Stains Test

You do NOT need to memorize which fibers correspond to certain tests (but you should be able to use test (e.g., flame test) flow charts to narrow down fabric type)

• Natural Fibers - Animals → Flame Test (smells like burnt hair), Acid/Base Test (silk dissolves with acid and wool dissolves with base), and Stain Test (wool strongly binds dye)

• Natural Fibers - Plants → Flame Test (smells like burnt paper) and Acid Test (all plants dissolve in acid)

• Natural Fibers - Minerals → Flame Test (does NOT burn) and Acid Test (dissolves fiberglass, not asbestos)

• Natural Fibers - Regenerated Fibers → Flame Test (melts) and Acid Test (dissolves regenerated fiber)

• Natural Fibers - Synthetic Fibers → Flame Test (melts) and Acid Test (dissolves nylon, not other synthetic fibers)

How can fabric (as opposed to individual fibers) be used for identification?

The method in which fibers are woven into fabrics may also yield identifying characteristics: weave patterns, thread counts, and yarn ply

What is birefringence, and how can it help analyze fibers?

Birefringence - an optical property that has to do with the refractive (light-bending) index

Fibers made of plastic materials (not all plastics) will emit colors in birefringence, which can be used to differentiate materials

What are the 4 main components of auto paint? (electrocoat, surfacer, basecoat, clearcoat)

Electrocoat Primer: 1st layer

• Function: Corrosion resistance on the steel body of the car (protects the car from corrosion)

• Contains epoxy-based resins & color ranges from black to gray

Primer Surfacer: 2nd layer

• Function: Smooth out and hide the seams or imperfections (typically not vehicular) (provides base for basecoat)

• Contains epoxy-modified polyesters or urethanes & color complements the topcoat

Basecoat/Colorcoat: 3rd layer

• Function: provides color and aesthetics

• Integrity depends on UV and weather resistance

• Comprised of: Binder, Pirment, Solvent, and any extra additives

Clearcoat/Topcoat: 4th layer

• Function: improves gloss, durability, and appearance (extends protection)

• Most are acrylic or polyurethane-based

What are the 3 main components of the basecoat, and what are their functions?

1. Binder: typically solids that make pigments ‘stick’ to one another (glue)

2. Pigment(s): fine powder that is insoluble in the medium in which it is dispensed. Used to color and may be (in)organic in nature

3. Solvent (i.e., thinners): liquid (water, organic) makes the binder and pigment less viscous so that it can be more easily spread (eventually boils or evaporates off)

What are some ways we can compare/analyze paint? (e.g., physical and chem exams)

Physical Properties: under a microscope

• Paint layer sequence

• Thickness ratios of layers (needing multiple paint coats)

• Color of layers

Chemical Properties: oil-based, water-based, latex-based, etc

• Solubility

• Components of a paint chip

• Entire paint chip: chromatography

• Individual layers: infrared microscopy

What is soil comprised of, and how does water retention help inform us of its texture?

Living Components: vegetation, bacteria, and animal matter

Non-Living Components: glass, paint, asphalt, water and air (how compact the soil is), rocks, and minerals

What are soil profiles, and how do horizons help determine location as well as depth?

O - Humus - organic layer

A - Topsoil - minerals + decaying organics

E - Eluviation - sand and silt

B - subsoil - clay and minerals

• Normally, where buried bodies get put

C - Parent/Broken Rock

R - Bedrock - little erosion, solid bedrock

Why is sand the most identifiable of the soil components? Where does sand come from?

The maturity of sand can indicate where it could have come from

Mineral compositions of sand can change its color, making it highly indicative of certain locations

How does soil chemistry (pH and nutrients) vary when bodies are buried/decompose?

The body is buried (or laid on top of the ground)

Toxic decomposition chemicals are released

Toxins kill the surrounding plant life

• Cadaver decomposition island (CDI)

Nutrient-rich decomposition fluids are released

• Soil pH and elemental composition will fluctuate around the decomposing body

• VOCs start to degrade = volatile organic compounds

How might one go about collecting soil?

Record location and description of the scene

Photograph the scene and the evidence

Sketch scene

Collection of soil evidence (at least 4 tbsp)

• Surface soil (for a baseline)

• Soil that looks different from the surrounding soil

• Soil from different levels

• Soil from objects (e.g., shoes, tools, vehicles, etc) from the scene

Collection of soil from outside of scene

• E.g., from several feet N, E, S, and W of the scene

Document, package, and label

Given the components of soil, how might it be analyzed to yield pertinent information?

• Microscopic Analysis can reveal location: decomposing organisms, spores/pollen, and coral or shell fragments

• Macroscopic Analysis can show pertinent evidence: bullet casings, knives, sawdust, glass, bones, oils, and flowers

• The value of soil as evidence rests with its prevalence at crime scenes and transferability between the scene and the criminal.

• Most soils can be differentiated by their general appearance