Forensic Science Test 3: Drugs, Arson, toxicology, and ted bundy

These flashcards cover key concepts related to forensic science, arson investigations, and criminal behavior based on the lecture notes.

Arson

The willful and malicious burning or exploding of property.

Explosion

The sudden conversion of potential energy into kinetic energy, resulting in a rapid release of heat, gas, and pressure.

Combustion

A chemical reaction that involves the rapid oxidation of a substance, producing heat and light.

Fire Tetrahedron

The four elements necessary for fire: heat, fuel, oxygen, and a chemical reaction.

Ignition Temperature

The minimum temperature required to start a fire in a given material.

Heat of Combustion

The amount of heat released when a substance undergoes combustion.

Conduction

Transfer of heat through direct contact between materials.

Convection

Transfer of heat through the movement of fluids (liquids or gases).

Radiation

Transfer of heat through electromagnetic waves.

Backdraft

An explosive burning of superheated gases that occurs when oxygen is reintroduced to a fire.

Pyrophoric Chemicals

Substances that spontaneously ignite upon exposure to air due to low activation energy.

Accelerant

A substance used to speed up the burning process, commonly used in arson.

Line of Demarcation

The boundary between burned and unburned areas that may indicate the direction of fire spread.

DNA Extraction

The process of isolating DNA from cellular components for analysis.

STR Markers

Short Tandem Repeats; segments of DNA used for genetic profiling.

Birefringence

The optical phenomenon that occurs when a light wave passes into a substance and splits into two rays.

Density

The mass of a substance per unit volume, an intensive property that remains constant regardless of sample size.

Refractive Index

A measure of how much light bends when it enters a material, differing depending on the medium.

Electromagnetic Radiation

A form of energy that travels through space as waves and can also be described as particles called photons.

Forensic Microscopy

The use of microscopes to examine evidence at a very small scale, including biological samples and fibers.

Necrophilia

A paraphilia involving sexual attraction to corpses.

Differential DNA Extraction

A method for isolating DNA from different types of cells in a mixed sample, particularly useful in sexual assault cases.

Fire

the rapid oxidation process with the evolution of heat and light

Methods of Heat Production

• Chemical

• mechanical

• electrical

• nuclear

Forms of heat transfer

• conduction

• convection

• nuclear

Phases of fire

• Incipient

• free burning

• backdraft

• pyrophoric chemicals

incipient (first phase of fire)

lasts anywhere from a fraction of a second to several hours or days depending on the fuel or ignition source (emerging smoldering)

Free Burning (second phase of fire)

the rate and intensity of open burning increase. The intensity of the fire doubles with each 18 F increase in temp. (heat is transferred through convection, conduction and radiation)

Backdraft (third phase of fire)

if you were to introduce oxygen back into the room, backdraft would occur (occurs at an explosive rate)

pyrophoric chemicals (fourth phase of fire)

combustion reactions require more activation energy than is present at room conditions (react upon introduction to air: very low activation energy)

line of demarcation

• black and clear area

• above the line of demarcation the potentially combustible smoke follows the path resistence

what is the most commonly used liquid accelerant?

Gasoline

Solid Accelerant Examples

Paper, fireworks, flares, black powder

Gaseous Accelerant Examples

butane, propane, natural gas (does not leave residue)

Liquid Accelerant Examples

petrolium distillates, non-petroleum products

Fire Analysis Types

• ASTM

• Liquid: GC-FID or GC-MS

• Sample preparation: cold or heated headspace, extraction, purge and trap, charcoal strip/SPME

What distinguishes an explosion from combustion?

The speed at which the reaction occurs

What is one of the first and most famous explosives?

Nitroglycerin which was invented in 1847

Evidence Collection (DNA sequencing)

evidentiary samples are brought or shipped to the DNA laboratory after collection from the crime scene or victim (can take various forms)

Sample collection (first step of DNA sequencing)

cotton swabs are commonly used to collect biological material (either directly from the source or evidence items) amount of material needed for typing has decreased with new methods

Forensic Serology (second step of DNA sequencing)

confirming type and presence of body fluids (types of testing: presemptive: used for screening confirmatory: used to confirm what body fluid is present)

• sperm may not be present if a vasectomy has taken place

DNA extraction (third step of DNA sequencing)

isolating the DNA from all other cellular components (for single fluid types involves: cell lysis and digestion, DNA precipitation, DNA resuspension)

Differential DNA extraction

used when processing sexual assault evidence

Assess DNA quality and quantity (fourth step of DNA sequencing)

determined by quantitative PCR, one copy is turned into thousands, primers fluorescently labelled, measures in real time amount of DNA

STR Typing and Markers (5th step of DNA sequencing)

STRs are repeats of 2-8 bases: at an STR locus an individual either: homozygous (same # repeats), heterozygous (different # repeats)

(short tandem repeats (STRs) are the best)

physical properties

examples are weight, volume, color, boiling point, and melting point describe a substance without reference to any other substance

chemical property

describes the behavior of a substance when it reacts or combines with another substance

Matter forms

solid- definite shape and volume

liquid-specific volume, takes the shape of its container

Weight

the force with which gravity attracts a body

mass

the amount of matter an object contains independent of gravity

density

the mass per unit of volume (D=M/V)

Intensive Property

remains the same regardless of sample size

refractive index

light waves travel in air at a constant velocity until they penetrate another medium, such as glass or water at which point they are suddenly slowed, causing the rays to bend. (the bending of light rays is due to change in velocity which is called Refraction)

Example of refraction

water looks bent in a glass of water

how does double refraction form?

crystalline solids have definite geometric forms

Birefringence

the numerical difference between these two refractive indices

wavelength

the distance between two successive crests

frequency

the number of crests passing any one given point per unit of time

theory of light

as electromagnetic radiation space moves through space, its behavior can be described as that of a continuous wave; however, once radiation is absorbed by a substance

photon

discrete particles of light

what does LASER stand for?

light amplification by stimulated emission of radiation

tempered glass

stronger than normal glass due to rapid heating and cooling of the glass surfaces

laminated glass

found in car windshields has a layer of plastic between two pieces of ordinary window glass.

How to know which shot came first on glass?

A is the first bullet shot because it creates the main cracks and B’s cracks just go up to the cracks on A and don’t go past

total magnification

magnification of ocular lens x magnification of objective lens

microanalysis

application of a microscope and microscopical techniques to observe, collect, and analyze mocro-evidence

basic microscopy

visible and infared spectrophotometry via a microscope

stereo binocular microscope

employed in the preliminary evaluation of submissions

compound binocular microscope

• schools and medical laboratories

• obtains morphological or structural information

resolution

the degree to which a microscope can distinguish fine details

depth of focus

to focus in different planes, move stage up or down

plane polarized

light that is confined to a single plane of vibration is said

The ability of an objective lens to resolve detaisl into seperate images is directly proportional to its _______ .

numerical aperture

Crystals that are ________________ produce two planes of polarized light, each perpendicular to the other.

birefringent

By using the _______________, one can view a particle under a microscope while a beam of light is directed at the particle in order to obtain its absorption spectrum.

Microspectrophotometer

If a polarizer and analyzer are placed (perpendicular, parallel) to each other, no light penetrates. 

Perpendicular

A(n) ______________ collects light rays from the base illuminator and concentrates them on the specimen.

Condenser

Light confined to a single plane of vibration is said to be ______________.

Plane-polarized

Two monocular compound microscopes properly spaced and aligned describe the ________________ microscope.

Stereoscopic

Each microscope lens is inscribed with a number signifying its __________ .

Magnifying power

The stereoscopic microscope offers a large _______________ between the objective lens and the specimen.

Working Distance

True or False: A bridge is used to join two independent objective lenses into a single binocular unit to form a comparison microscope.

True

A microscope that remains in focus regardless of which objective lens is rotated into place is _______________.

Parfocal

True or False: The coarse and fine adjustments are part of the microscope's mechanical system. 

True

The size of the specimen area in view is known as the ____________ .

Field of view

The depth of focus (increases, decreases) with increasing magnification. 

decreases

cuticle

paint on a pencil: the cuticle is the exterior covering of the hair. It is made up of a series of overlapping scales

Coronal Scales

• scales show crown-shaped pattern

• found in small rodents and bats

• never seen in human hair****

spinous scale

• scales show petal-like triangular pattern

• found close to the body on mink. Also seen on seals, sea lions, fox, and cats

• NEVER seen in human hair ****

imbricate scales

• scales show brick like or flattened pattern

• tightly overlapping scales with narrow margins

• usually only found in human hair; although could be seen in some animal species

cortex (second layer)

wood part of pencil: the cortex contains the pigment

cortical fusi

irregular shaped airspaces

medulla (center layer)

Pencil lead: the medulla is a column of cells that runs through the center of the hair

anagen phase

• active growth phase

• can remain in this phase for up to ~6 years

• 80-90% of hairs are in the anagen phase

telogen phase

• dormant/resting phase

• lasts 2-6 months

• hair is easily removed

• 10-18% of hairs are in the telogen phase

Catagen phase

• transitional phase between anagen and telogen

• lasts 2-3 weeks

• less firmly held than anagen

• 2% of hairs in this phase

Body area origin examples

• head hair

• pubic hair

• facial hair

• axillary hairs

• eye hairs

racial origin

asian: round

european: oval

african: flattened

pigment pattern

caucasian: even

negroid: splotchy

moonogoloid: streaky

Can the age and sex of an individual be determined from a hair sample?

No