Forensic Science - Unit 2 Test

Forensic Science

application of science to both civil and criminal laws that are enforced by police agencies

Locard’s Principle

when 2 objects come into contact with one another, there is an exchange of materials between them

Physical Science Unit

examine physical and trace evidence

Biology Unit

DNA profiling, hair and fiber analysis, bodily fluids, plant/wood analysis

Firearms Unit

bullet, firearms, trajectory, direction and source, residue

Documentation Unit

handwriting, typewriting, ink, paper, erasures

Photography Unit

record and analyze evidence via special photographic techniques

Toxicology Unit

examine fluids and organs for presence of drugs and poisons

Latent Fingerprint Unit

process/examine latent fingerprint evidence

Polygraph Unit

administer lie detector test and analyze results

Voice-print Analysis Unit

analyze telephone threats and record messages

Crime Scene Investigation Units

collects and preserves physical evidence

Psychiatry

examine behavior and examine competency to stand trial or verify insanity plea

Odontology

dental records, bite marks

Engineering

failure analysis, accident reconstruction, causes/origins of fires/explosions

Computer & Digital Analysis

identification, collection, preservation, analysis of data from computers & digital devices

Entomology

study of insects to determine time of death/location

Pathology

determine the cause of death & autopsy

Anthropology

analysis of bones

CSI Effect

television shows provide individuals with unrealistic expectations regarding the collection, processing and analysis of evidence and crime solving due to misinformation, quick results, all-knowing 

Who secures the crime scene?

The first arriving officer

Individual Characteristics

properties of evidence that can be attributed to a common source with an extremely high degree of certainty (fingerprints)

Class Characteristics

properties of evidence that can be associated only with a group and never with a single source (car paint for a specific make)

IAFIS

national fingerprint database

CODIS

DNA profiles

NBIN

firearms and bullet marks

PDQ

automotive paint

SICAR

shoe prints

NamUS

missing persons

Identification

the process of determining a substance’s physical or chemical identity with as near certainty as existing analysis techniques allow

Comparison

the process of ascertaining whether two or more objects have a common origin by testing a suspect specimen and studying a standard/reference sample

Manner of Death

the determination made by a forensic pathologist of the cause of death and there are five broad categories: homicide, suicide, accidental, natural, and undetermined

Homicide

non-accidental death resulting from grossly negligent, reckless or intentional actions of another person

Suicide

death caused by an individual taking his/her own life lethal intentions

Accidental

death that resulted without intent to cause harm through gross negligence on part of the perpetrator or the victim

Natural

deaths resulting from disease or continual environmental abuse (habitual drug use, exposure to chemicals over long periods of time)

Undetermined

only used in cases where rational classification cannot be made based on the physical finds of an autopsy or the absence of anything meaningful in toxicological and microscopic examinations

Periodic Table

table/chart with all the known elements

Melting

solid —> liquid

Sublimation

solid —> gas

Freezing

liquid —> solid

Deposition

gas —> solid

Condensation

gas —> liquid

Vaporization

liquid —> gas

Solids

definite shape and volume; most dense, particles close + vibrate

Liquids

indefinite shape, definite volume & flow

Gases

indefinite shape and volume; chaotic, random, rapid

Density

density = mass/volume

will float if substance is less dense

will sink if substance is more dense

Dispersion

separation of light into colors

Refraction

the bending of light (ex: fish in water)

Glass

made of heated sand (main component) and mixed metal oxides; hard brittle, amorphous solid

Soda-lime

windows, glass bottles

Borosiliscates

headlights, pyrex

Tempered

side and rear automobile windows

Laminated

windshield

Flotation

a method of changing the amounts of liquid until the solid glass is suspended (density of liquid = density of the glass)

How can the bullet holes in glass determine the direction of penetration/exit?

the hole is wider on the exit side

How to determine the sequence of bullet holes made in glass?

look at where each fracture ends or terminates; the first hole’ fracture will not terminate at another fracture while the second will have fractures that end at the first

Hair

hair is an appendage of the skin

Cuticle

snake-like outermost layer of hair

Cortex

2nd layer in hair w/pigment

Medulla

cells like central canal

What layer of hair is most often used to determine the species it came from?

cuticle

What layer of hair contains the pigments that give hair its color?

cortex

Anagen

1st stage of growth (up to 6 years)

Catagen

2nd stage, slower growth (2-3 weeks)

Telogen

3rd stage, hair is pushed out and naturally shed

How can hair be used to determine the gender from which it came from?

DNA (in follicle)

What is the most common plant fiber used to make clothing?

cotton

How should fiber evidence be collected and stored?

bagged separately; if loose, removed w/forceps and placed in a small sheet of paper

What instrument should be used to compare the color fo fiber evidence and why?

visible light microspectrophotometer; small sample sizes and nondestructive

What properties are used to compare synthetic fibers?

color and diameter

What is cellulose and where is it frequently found in nature?

natural polymer found in the woods

Proton

positive charged particle found in the nucleus

Neutrons

neutral particles found in the nucleus

Electrons

negative particles found outside the nucleus

Isotope

an atom with the same number of protons (atomic number) but different number of neutrons (masses)

Neutron Activation

a highly sensitive and nondestructive analysis method for identifying trace elements. Uses a nuclear reactor to provide a source of neutrons to bombard atoms producing radioactive isotopes. To identify the radioactive isotopes one must analyse/measure the energy of the released gamma rays

What types of crime often leave paint evidence?

hit-and-runs

What can be determined about a vehicle using the PDQ database?

make, model, and year

Pyrolysis gas chromotography & uses

solid materials including paint are heated so they will decompose into numerous gaseous products to flow through the GC column that produces a program that can be used to identify and compare the binder makeup of paint samples

What is first looked for/at regarding soil evidence?

gross appearance using low magnification

How is soil evidence collect & preserved?

any object with suspected soil samples should be collected and packaged separately in leak-proof containers

reference samples should be collected from various points within a 100-foot radius of the scene and then packaged in a druggist fold or a solid container