Fundamentals of Forensic Science - Final Exam Review

What are filaments?

type of fibers having indefinite or extreme length, such as silk of manufactured fiber

Dye (fiber)

an organic chemical that is able to absorb and reflect certain wavelengths of visible light

TLC (fiber color)

• Addresses type of dye used to color fiber and may help sort out metameric colors

• A destructive method

Primer

usually an epoxy resin with corrosion-resistant pigments

How are soil samples homogenized before sampling?

• Determine particle size distribution first

• Samples are then crushed and pulverized to make them consistent throughout

• Allows for physical and chemical analyses to be extrapolated to the bulk sample

What are common dopants glass?

Soda, lime, boron oxide

Informal signature

would be used in routine correspondence where the writer wants the reader to recognize the signature

Very few internal or external components of a computer system can hold some form of data or metadata that could be useful forensically.

False

If initial information is consistent between the known and questioned bullets, what is the next step?

Microscopical comparison

What is thread?

the product used to join pieces of fabric together

What is plied yarn?

a yarn constructed of a number of smaller single yarns twisted together

Synthetic fibers

those manufactured fibers that are synthesized from chemical compounds

Cross section is an important characteristic and is indicative of end use

True

Fluorescent components and their response to certain wavelengths of light can be useful in comparing textile fibers.

True

Pharmacology

the study of the relationships between drugs and living things

What are the processes of pharmacokinetics?

-absorption, distribution, metabolism, and elimination

-A dynamic equilibrium of drug within the body is dependent on these processes

Distribution (Pharmacokinetics)

• A drug may be distributed locally by diffusion through tissues

• Global distribution through the body is accomplished by way of the bloodstream

• Portion of a drug may bind to blood proteins; must account for this in determining effective concentration

• Concentration of drug is not the same everywhere (more blood in brain, heart, and liver)

What does the cross sections of paint samples provide?

information about layers, thicknesses, colors, and size and distribution of pigments

Solvent and microchemical tests (paint)

-Layers of paint, with different chemical compositions, will react differently to oxidizing, dehydrating, or reducing agents

-Destructive tests

-Should be performed on known and questioned samples simultaneously

-Record effects immediately and for duration of test

Color systems

used to classify colors for description and communication of color information and for databases only

What are forensic geologists concerned with?

-The transfer of soil particles from locations to objects

-with questioned or unknown samples, as well as known or control samples

Collection of soil evidence

-Collect all layers of soil at once and intact: Can help establish the order of contact with soil present at various locations

-Collect and preserve as much questioned evidence as possible

-Control samples should be taken from a location as close to evidentiary samples as possible

-May be collected from several areas to account for variation in soil

-Vertical and horizontal layering are important

-Time is also a consideration (area may have been disrupted)

_____________________ is used to give a profile of organic substances found in the soil.

High performance liquid chromatography (HPLC)

What observations should be included from projectiles on glass?

where projectile ends up, formation of crater in the glass, formation of a cone of glass, and types and positions of cracks that appear in the glass

_______________ is the backbone of a series of designer drugs that are synthesized with particular pharmacological characteristics designed for abuse purposes.

Fentanyl (China white)

Phencyclidine (PCP)

• First marketed as anesthetic

• Causes feelings of no pain sensation, superhuman strength, rage, loss of memory, and paranoia in humans

• Considered now to have no medical use, controlled as Schedule I

What are the questions to answer in developing a drug analytical scheme?

• How are the controlled drugs defined and described in this jurisdiction?

• Are the weight of the drug and/or the aggregate weight of the exhibit important?

• Must the identity of the drug be established and then confirmed?

• Is it necessary to determine the purity of the drug exhibit (quantitative analysis)?

• Is it necessary to identify any of the cutting agents present in the exhibit?

The weight of the drug is what in most state laws?

aggregate weight

Weight is also important where government wishes to punish the possession of one form of a drug more harshly than another.

True

Chromatography (illicit drugs)

• Used for separation purposes, not confirmation of a drug

• TLC can determine how many substances are present in an exhibit and what they might be

• GC, LC can give information about drug, excipients, and diluents

• Can be used as part of confirmation methods, i.e., GC/MS

Quantitative analysis (illicit drugs)

• GC or GC/MS is almost always used

• LC works well too

• Internal standard must always be used

Bertillionage

-a complex system of anthropometric measurements, photographs, and descriptions

-Alphonse Bertillion

-Complicated, involved process

-Difficult to standardized and replicate

-Imprecise objective definitions

What only factors may alter the friction ridge area?

Scarring or other trauma to the epidermal-dermal margin

Arches

-the rarest of the three main classes or patterns

-A plain arch has ridges that enter from one side of the finger, gradually rise to a rounded peak and exit the other side

-A tented arch is a pronounced, sharp peak

-Arches do not have type lines, cores, or deltas

Bifurcation

ridge split into two ridges

Level 2 detail (fingerprints)

_includes formations, defined as ridge endings, bifurcations, dots, or combinations of these features

-Sufficient for identification

-Relationship of these features enables individualization

What test can individualize fiber evidence?

Tear match

The line that appears to be formed at the boundary between two different refractive indexes:

Becke line

A questioned document doesn't have to be written on paper.

True

Fires and explosions are the result of a chemical reaction known as ________________.

Combustion

All combustions are exothermic reactions.

True

How is a fire determined to be started deliberately?

• All possible natural and accidental causes must be eliminated

• Determine if fire is arson

• Look for accelerant or

What is a critical step in the determination of the cause of a fire?

Determining the point of origin

How to investigate a fire scene?

• Make accurate, thorough records of investigation through still or video photography and good note taking

• Begin with general examination and work toward point of origin

Headspace

the vapor above the fire residue in a sealed container - can be used to analyze accelerants by injecting vapors into GC

Low explosions

-Deflagration velocities below 3,280 fps

-Oxygen is physically mixed with fuel

-Main effect is to push, not shatter, objects in path of blast wave

-Propellants in guns that fire bullets or shot pellets

-Examples include smokeless powder and black powder

-Can be used in pipe bombs

-Can detonate using a flame, spark, or chemicals, such as acids

Proportion (QD)

the symmetry of an individual letter.

Not normally possible to trace a document written on an ink-jet printer back to a specific machine.

True

What are some obstacles faced when collecting evidence from digital devices?

• Digital evidence requires an electrical power source to operate - may be lost or corrupted if power is not maintained

• Digital evidence can be overwritten or deleted remotely

• Moving some digital devices while powered may damage the device or any mechanical storage media

Media management analysis

The analysis of the organization of the storage media; determining the file structure or subsections of a storage device

Application analysis

The analysis of applications and their files, like documents, images, logs, configurations, and others

Single action revolver

requires that the hammer be cocked each time it is fired

What is the spread of pellets based on?

distance traveled and choke size

What tests can be used to detect primer residues?

dermal nitrate test and atomic absorption

Impression evidence

-When a donor object or a material is pressed against a recipient object or material and some force is applied, the donor may leave an impression in the recipient

-Involves a donor and a recipient

-Donor contains some three-dimensional markings

-Recipient is made of a material that can form and hold a negative image of the donor markings

Crime scene notes should provide the location, direction, and description of prints.

True

What 2 main groups can individualizing marks be broken into?

- manufacturing marks

-Marks that are created by use of the shoes

Impression evidence can be individualized if sufficient unique characteristics are present.

True

High explosions

• Detonation velocities above 3,280 fps

• Designed to shatter and destroy objects in path of blast wave

• Require severe shock for detonation to occur

• Accomplished using a blasting cap or primary or initiating explosive

• Break bonds holding fuel and oxygen together

• Reaction is from molecule to molecule, rather than from particle to particle, as is the case with low explosives

Fibers from textiles are constantly being shed and transferred to people, places, and things.

True

What are the differences between fibers?

-chemical nature

-cross-sectional shape

-surface contour

-color

-length

-diameter

What is a textile fiber?

a unit of matter, either natural or manufactured, that forms the basic element of fabrics and other textiles

What is a natural fiber?

any fiber that exists as a fiber in its natural state

What is a manufactured fiber?

any fiber derived by a process of manufacture from any substance which, at any point in the manufacturing process, is not a fiber

Protein fibers are composed of polymers of ______________________.

amino acids

Cellulosic fibers are made of polymers formed from ______________.

carbohydrates

Mineral (inorganic) fibers may be composed of silica obtained from ________________.

rocks or sand

Synthetic fibers are made of polymers that originate from ___________________.

small organic molecules that combine with water and air

What act established the generic names for fibers?

Textile Fiber Products Identification Act

What are staple fibers?

natural fibers or cut lengths of filament typically being 7/8 to 8 inches

Diameter of natural fibers is measures in what?

Micrometers

What is denier?

Weight in grams of 9000m of material fibrous

What is Tex?

the weight in grams of 1,000 meters of fiber or yarn

What is yarn?

-a term for continuous strands of textile fibers, filaments, or material in a form suitable for weaving, knitting, or otherwise entangling to form a textile fabric

-Constructed to have an S- or Z-twist or no twist at all

What is fabric?

-a textile structure produced by interlacing yarns, fibers, or filaments with substantial surface area in relation to its thickness

-Defined by method of assembly: woven, knitted, or nonwoven

What are woven fabrics?

fabrics composed of two sets of yarns, called warp and weft, and are formed by the interlacing of these sets of yarns

Warp yarn

run lengthwise to the fabric

Weft yarn

run crosswise; referred to as filling, woof, or picks

What are knitted fabrics?

constructed of interlocking series of loops of one or more yarns and fall into two major categories: courses and wales

Courses

rows of loops across the width of the fabric

Wales

rows of loops along the length of the fabric

Knitted fabrics are formed by multiple yarns.

False

What are nonwoven fabrics?

-an assembly of textile fibers held together by mechanical interlocking in a random web or mat, by fusing of the fibers, or by bonding with a cementing medium

-Ex. felt, bandage pads, automotive textiles, and medical fabrics

Characteristics are imparted to manufactured fibers with particular end uses in mind.

True

Crimp

the waviness of a fiber expressed as crimps per unit length

How is color introduced to manufactured fibers?

Dyes or pigments

Natural fibers may be originally ______________.

white, off-white, or a shade of brown

What is cross sectional shape of a fiber?

the shape of an individual filament when cut at a right angle to its long axis

All fibers are chain-link macromolecules called polymers.

True

Over half of the fibers produced each year are_________________.

natural fibers

What makes up most of natural fibers?

Cotton

Where do natural fibers come from?

animals, plants, minerals

Animal fibers

-Come from either mammals (hairs) or from certain invertebrates, such as the silk worm

-Wool-bearing animals, fur-bearing animals

What are the three major sources for fibers derived from plants?

- Seeds (blast fibers)

-Stems

-Leaves

Technical fibers

used in cordage, sacks, mats, etc. or individual cells, as in fabrics or paper

Manufactured fibers

the various families of fibers produced from fiber-forming substances, which may be synthesized polymers, modified or transformed natural polymers, or glass

How are synthetic fibers made?

by extruding a fiber-forming substance, called spinning dope, through a hole or holes in a shower headlike device called a spinneret

Color is a discriminator of fibers that have been dyed or chemically finished.

True

What two assessments of fiber colors must be part of every fiber comparison?

Visual and analytical

Thermal properties

relate to the softening and melting temperatures for manufactured fibers and the changes the fiber exhibits when heated