CSI/QAC Exam 2

Is it possible to individualize 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)

Root shape and size are determined by the hair’s growth stage

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

The concentration is highest in Anagen (growing phase)

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?

6 Horizons:

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 (broken down rock and sediment). Mineral compositions of sand can change its color, making it highly indicative of certain locations

Sand formation → weathering of rocks/minerals, skeletal remains, and broken shells

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

What is toxicology, and how does it relate to pharmacology, pharmacokinetics, and pharmacodynamics?

Toxicology - the study of the adverse effects of toxicants (poisons) on living systems. Forensic Toxicology is a subsidiary of pharmacology, the study of drugs and their harmful or beneficial effects on living things.

Pharmacokinetics - what the body does to a drug

Pharmacodynamics - study of what drugs do to the body

How do drugs change after they enter the body (especially alcohol)?

Drugs enter the body and become metabolized into their metabolites at different rates

What are some of the general areas to which toxicological techniques are applied?

Field Testing, (DRE), drug analysis, Medical Examiner (death investigation)

Explain the metabolism (in general) of alcohol. What are the stages? When does BAC peak? Can the alcoholic user control the rate of absorption? How is alcohol eliminated?

Alcohol - Absorbed in the body within minutes after it has been ingested. Increases in concentration during absorption. Mostly from the stomach and small intestine

When absorption is complete, alcohol becomes uniformly distributed between all the watery portions of the body, which is about two-thirds of body volume.

The maximum BAC level is reached when all the alcohol has been absorbed

Alcohol is eliminated through oxidation and excretion

• Users can control their rate of absorption by the mode of absorption, the nature of the drink, whether they’re drinking on a full/empty stomach, and how fast they are drinking

What are the ways to test for alcohol? What is field testing? What is a DRE?

Field Testing - sobriety tests and evidentiary breath tests (breathalyzers)

Drug Recognition Expert (DRE) - The DRE program incorporates standardized methods to determine whether a suspect has taken one or more drugs. E.g., blood pressure, pulse, pupil size, etc.

• Police or designated DRE - evaluates impairment

What is Henry’s Law? How can alcohol concentration be determined via exhalation?

" At constant temperature, the concentration of a dissolved gas in a liquid is directly proportional to the partial pressure of that gas in equilibrium with the liquid."

Moves from high concentration to low (drugs, gas, etc.)

Devices use methods like infrared spectrometry or fuel cells to analyze the breath samples 

Which breath testers are admissible in court?

PBTs (preliminary breath testing) are not admissible in court

EBTs (evidentiary breath testing) are admissible in court

How do blood-drawn alcohol tests differ? What machines are used?

Gas chromatography offers the toxicologist the most widely used approach for determining BAC in blood. Ethanol can be separated and analyzed via GC.

Hospital or clinical labs normally use autoanalyzers to measure alcohol content.

• Measures the conversion of alcohol by alcohol dehydrogenase

• Detection of the resulting metabolite (NADH) by spectrophotometry

How are non-alcoholic drugs screened and confirmed?

A significantly more complex problem than alcohol. Toxicologists are presented with body fluids and/or organs. Normally requested to examine them for the presence of drugs and poisons.

Sometimes analyses must be done WITHOUT supportive evidence:

Must also assess the TOXICITY of the drug or poison, which differs based on the person.

What is the difference between testing for toxicity and identity vs impairment?

Impairment determines if a substance or condition is currently impacting an individual’s function or behavior

Identity confirms the chemical makeup of a substance, and toxicity is the potential to cause bodily harm to an individual (dosage)