CSI exam 2

hair fibers + paint + soil + drugs

Can a human hair be individualized by morphology alone?

No - it is not possible yet. morphology alone = class characteristics.

What allows partial individualization of hair?

Isolating and characterizing DNA in hair.

Hair without a follicle provides what type of characteristics?

Class characteristics.

Hair with a follicle provides what type of characteristics?

Individual characteristics (nuclear DNA).

What are the 3 layers of the hair shaft?

Medulla (center), cortex (middle w/ pigment), Cuticle (outer)

In which direction do cuticle scales point?

Toward the tip of the hair.

Why is the shaft the most examined part of the hair?

Because roots (with nuclear DNA) are harder to obtained at crime scenes (degradation + shed hairs lack the follicular tag)

What are the 3 cuticle patterns?

Coronal, Spinous, Imbricate.

Coronal scales look like

A stack of paper cups

Spinous scales look like 

Petal-like/ triangular, protruding.

Imbricate scales look like

Flattened, overlapping scales with narrow margins.

why is the cortex important?

It contains pigment granules - color, shape, and distribution are key comparison points.

What is the medullary index for humans vs animals?

Humans smaller or equal to 1/3, animals bigger than or equal to 1/2.

What medulla pattern do NE Asian and Oceania individuals commonly have?

Continuous medulla in head hair.

List the 3 hair growth phases.

Anagen (growth), Catagen (transition), Telogen (rest/shedding).

Which phase has the MOST nuclear DNA?

Anagen phase (active growth = most DNA).

What is a follicular tag?

Translucent tissue around the root; rich source of nuclear DNA.

Where is mtDNA found in hair?

In the hair shaft (outside the nucleus).

Why can mtDNA NOT individualize?

Maternal inheritance; shared among maternal relatives.

Can racial origin sometimes be determined from hair?

Yes; e.g., continuous medulla in some Asian ancestries.

Can sex be determined from hair morphology?

No.

Can age be determined from hair morphology?

Only infant hair (fine and short).

Can you determine if hair was forcibly removed?

Possibly; follicle or sheath cells may be present.

How many reference hairs are required?

25 head hairs + 25 pubic hairs.

Two major categories of fibers.

Natural fibers and Synthetic fibers.

Most prevalent plant fiber.

Cotton; ribbon-like with twists.

Flame test: smell of burnt hair indicates what fiber type?

Animal fibers.

Flame test: smell of burnt paper indicates what fiber type?

Plant fibers.

Acid test dissolves which fibers?

Plant fibers, silk, fiberglass, regenerated fibers, nylon.

Base test dissolves which fiber?

Wool.

Regenerated fibers are made from what?

Natural raw materials such as cellulose.

Synthetic fibers are made from what?

Chemicals such as nylon, polyester, acrylics.

What was the first synthetic fiber?

Nylon.

Steps to compare fibers microscopically.

Compare color → compare diameter → examine striations, pitting, cross-section shape.

What does birefringence tell you?

Fiber has different refractive indices; helps identify fibers.

What are the 4 layers of automotive paint?

Electrocoat primer → Primer surfacer → Basecoat → Clearcoat.

Function of electrocoat primer.

Corrosion resistance.

Function of primer surfacer.

Hide seams and imperfections.

Function of basecoat.

Provides color and aesthetics.

Function of clearcoat.

Provides gloss, durability, and appearance.

Components of the basecoat.

Binder, pigment, solvent, additives.

What does the binder do in paint?

Makes pigments stick together.

What does the solvent do in paint?

Makes the mixture less viscous for spreading.

Paint chips vs paint smears.

Chips = intact layers; Smears = usually only topcoat.

Should tape lifts be used for paint evidence?

No.

Where should known paint samples be collected?

Near point of damage from undamaged paint.

How can paint be excluded?

Layer structure differences.

Two major chemical paint techniques.

Pyrolysis-GC and Infrared microscopy.

Definition of soil.

Disintegrated material near Earth’s surface with living and non-living components.

Three main soil particle types.

Sand, silt, and clay.

Which soil retains the least water?

Sand.

Which soil retains the most water?

Clay.

List the six soil horizons.

O, A, E, B, C, R.

Which horizon are bodies normally buried in?

B-horizon (subsoil).

Four types of sand.

Continental, volcanic, skeletal, precipitate.

Why is sand highly identifiable?

Location-specific composition (quartz, mica, olivine, coral, basalt, etc.).

What forms a cadaver decomposition island (CDI)?

Toxins + nutrient-rich fluids altering soil pH and composition.

Minimum soil amount to collect.

4 tablespoons.

Where to collect soil from.

Surface, different depths, objects, and reference areas N/E/S/W.

Who said “Dosage makes the poison”?

Paracelsus.

Two major tasks of forensic toxicology.

Identify & quantify poisons; interpret effects on individual.

Define pharmacokinetics.

What the body does to a drug.

Define pharmacodynamics.

What the drug does to the body.

Agonist vs antagonist.

Agonist activates receptor; antagonist binds but blocks action.

What % of poisoning deaths are caused by drugs?

90%.

Ethanol acts as what type of drug?

Depressant affecting the CNS.

Three stages of alcohol metabolism.

Absorption → Distribution → Elimination.

Where is alcohol absorbed?

Stomach and small intestine.

Does food slow alcohol absorption?

Yes; empty stomach = 30–90 min, full stomach = 2–3 hours.

Where is alcohol oxidized?

Liver via alcohol dehydrogenase.

What does Henry’s Law allow?

Using breath alcohol concentration to estimate BAC due to 2100:1 ratio.

Which breath testers are admissible?

Evidentiary breath testers; PBTs are not admissible.

Two breath tester technologies.

Infrared absorption and fuel cell oxidation.

Legal BAC limit in the US.

0.08%.

Commercial driver BAC limit.

0.04%.

Best confirmatory method for drug ID.

GC/MS.

Screening tests include what?

Gas chromatography and immunoassay (ELISA).

Confirmation tests include what?

GC/MS.