Download Forensic Science Final Exam Review Topics

Forensic Science Final Exam Review Topics
Introduction and History of Forensic Science
Forensic science – the application of science to law
Evidence – anything that can be used to determine whether a crime has been committed
Famous Scientists – Know what their contribution was to forensic science
 Edmond Locard and the Locard Exchange Principle – if two objects come into contact there will be a cross
transfer of material
 Francis Galton – famous for his work with fingerprints
 Alphonse Bertillon – used a series of body measurements to identify someone
 Calvin Goddard – ballistics and firearms
 Karl Landsteiner – famous for his work with blood typing
 Hans Grosse – founder of criminalistics as an academic discipline
Famous Court Cases – What precedent did they set?
 Frye v. U.S. – created guidelines for forensic science, evidence must be generally accepted by the scientific
community to be admissible in court
 Daubert v. Merrell Dow Pharmaceutical – evidence must be accepted by the trial judge to be admissible in
court
Crime Scene – Process and collect evidence
 How do you preserve evidence?
o Chain of custody – continuous record showing that evidence has been kept safe and secure.
 How should evidence be collected?
o Each item is packaged separately
o Blood should be packaged in paper bags to allow blood to dry in order to reduce mole and mildew
growth
o Ashes should be sealed in air tight containers (such as a clean, new paint can) to trap volatile gases
o Hair, fibers, glass, and other trace evidence can be sealed in envelopes, pharmacy folds, or pill
containers
 Individual characteristics – characteristics associated with a single source – wear and damage on shoes,
defects, alterations
 Class characteristics – characteristics associated with a group and not a single source – size of shoe, tread
pattern, logos, brand
 Physical properties – describes a substance using observation
 Chemical properties – describes the behavior of a substance when it reacts or combines with another
substance
Time of Death and Autopsy
Determine Time of Death Using
 Forensic Entomology – the use of insects in investigating crime
o Blowflies are the first to arrive on a corpse
o Factors that affect the stage of development for blowflies: temperature and weather
 Algor Mortis – estimated time of death determined by body temperature. The body cools 1.5ᵒF every hour.
(98.6 – Body Temperature/1.5). However, this estimation is only good for the 1st 24 hours after death.
o Factors affecting body temperature: air temperature, location (sunny, shady, wet, dry), clothing,
weather)
 Rigor Mortis – body stiffening due to build up of lactic acid and pyruvic acid after death
 Cadaveric spasm - instantaneous rigor, a rare form of muscular stiffening that occurs at the moment
of death, can be mistaken for rigor mortis. Usually associated with violent deaths, specifically affecting
muscles in the forearms or hands.
 Livor Mortis (lividity) – settling of blood close to the ground after death
Autopsy
 Medical Examiner – appointed in Maryland, and are licensed physicians trained in death investigation
Trace Evidence
Hair
 Cuticle – scales on the outside of the hair. Humans have an imbricate pattern (shown below, to the right)
 Cortex – main body of the hair shaft
 Medulla – middle of the hair shaft. Shows great variation among people and species. Under high
magnification, the basic internal structure of the medulla is referred to as the medulla index. Some of the
major medulla indicies include vacuolated (dog), unisereal (cat), lattice (deer or elk), multisereal (rabbit),
and fragmented and continuous amphorous (human).
o Humans with black hair tend to have continuous amorphous medullas, while other hair colors tend
to have fragmented amorphous medualls.
Fiber
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Paint
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Glass
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Structure of fibers
o Polymers are made of monomers
Tests used to analyze fibers and their dye
o Microscopic examination
o Burn test
o Dyes in fibers can be analyzed using chromatography
Analysis of paint evidence is done by pyrolysis gas chromatography
Binder formulations are the most significant information for paint evidence
Radial fractures – cracks in glass that extend outward like spokes on a bike wheel
Concentric fractures – circular cracks in glass
Becke line – halo around glass when placed in a liquid with a different
refractive index
Refractive index – the ability of glass to bend light
Measurements of glass – done by refractive index and density by
floatation (water displacement to determine volume and mass glass
using a balance)
Arson
 Combustion reaction (a type of oxidation reaction): hydrocarbon fuel
source + O2  CO2 + H2O
 Accelerants – any material used to sustain or start a fire. Best identified by gas chromatography.
 High explosives – supersonic shockwave with high velocity charge
 Low explosives – rapid oxidation followed by subsonic pressure wave
 Characteristics of serial arsonists – white, male, loves fire, violent past, perhaps a firefighter or volunteer
firefighter, observes the fire
Document Analysis
 Be able to match handwriting from unknown to known
 Techniques used to analyze document for erasures, obliterations or alterations
o Infrared radiation is used to determine original writing if a suspect may have tried to chemically
obliterate part of a document.
 Voiceprint is determined by the frequency, time, and intensity
Fingerprints
 Recognize different minutiae
 Three basic principles of fingerprints
o Fingerprints remain unchanged throughout an individual’s lifetime
o Fingerprints can be systematically classified
o Each fingerprint is unique
 Latent fingerprints – prints that cannot be seen
 Methods of making latent prints visible (lifting)
o Physical – powder dusting for fingerprints
o Chemical – Ninhydrin, super glue fuming, iodine fuming
 Types of fingerprints: loops, whorls, arches
 Recognize different minutiae
o Bifurcation
o Short ridge
o Ridge crossing
o Island
o Ridge ending
Serology/Blood Splatter/DNA
Blood Type and identification
 Determining blood type using antiserums
o Blood types: A, B, AB – universal recipient, and O – universal donor
 If D is +, then blood type = A+
 If D is -, then blood type = A Agglutination of blood with antiserum means that the person has that blood antigen
 Three Questions about blood
o Is it blood?
 Kastle-Meyer Test – Phenolphthalein used to test stains to see if they are actually blood.
Positive result – cotton swab turns pink
 Luminol – used to test for the presence of body fluids (spray over questioned area)
o Is it human blood?
 Precipitin test
o Whose blood is it?
 Blood typing (not conclusive)
 DNA fingerprinting
 Gel electrophoresis - used to create a DNA fingerprint
o Restriction enzymes – used to cut DNA in order to create a DNA
fingerprint
o STR (short tandem repeats) – cut DNA at variable regions that repeat.
New typing that involves short tandem repeats.
Splatter
 Determining angle of impact - 90ᵒ angle of impact makes a circular spatter. As the angle decreases, the
shape of the spatter becomes more oblong.
 Determining point of convergence – indicates where the victim was standing based on the angle of impact.
Ballistics
 Determination of Caliber – measure the inside of the barrel from
land to land
 Larger exit wounds are a result of the bullet becoming deformed in
the body
 Burned skin and powder burns help to determine the distance from
the victim to the shooter. The greater the burn mark and amount of
gus shot residue present on the victim, the closer the victim was the
the gun.
Impressions
Shoe Prints
 How to make a cast of a shoe print in the soil: Secure the area and photograph the print. Place a casting
frame around the print. Pour the casting mix and wait for it to dry. Lift the cast, package, and send to the
lab. At the lab, remove excess soil and look for points of comparison (both class and individual).
 How to lift a residue print inside: Secure and photograph the area. Use Pathfinder to lift the print (an
electrostatic lifter). The section of the floor may have to be removed if the CSI does not believe the print
will be lifted effectively with Pathfinder.
Tool Marks
 Tool marks can be individualized by machining (striation marks)
Anthropology
 The pelvis bone is best for determining gender
 Other long bones that are useful: femur, humerus, radius, tibia
 If the hyoid bone is crushed in an adult, strangulation should be suspected as the cause of death
Serial Killers
 Typically there is an injury to the frontal lobe
 Typical profile of the serial killer – white, male, 20-30 years old, US citizen
 Ted Bundy is a classic serial killer – know his phases, how he fits the typical serial killer profile, organized
or disorganized, transient or stable
 VICAP
Drugs/Toxicology
Identification of Drugs and poisons
 First weigh and inventory the drug in question. Then make
visual observations.
 Screening tests: color tests, microcrystalline tests
 Confirmatory tests: IR spectrophotometry, UV
spectroscopy, GC/MS
 Know how to read a mass spectrum
 Know how to read a chromatogram
o Retention time – the time between sample injection
(time zero) and the appearance of the band
maximum. Phenobarbital has a longer retention
time than any other chemical/peak on the chromatogram, as shown to the right
 Classification of drugs:
o Narcotics – heroine, codeine, oxycotin
o Depressants – alcohol, barbiturates, tranquilizers (valium)
o Stimulants – amphetamines, cocaine
o Hallucinogens – marijuana, LSD, mescaline, PCP, ecstasy
 Marsh test – used to determine the presence of arsenic
 Know the process and machinery for GC/MS – One way to identify a compound is to identify how far each
part of it moves through an inert gas, or carrier gas. GC rapidly separates mixtures of compounds into
individual components in this manner. A technician injects a liquid sample into one end of the column,
where it is heated and vaporized. The vapor enters the column and flows with the moving carrier gas until it
reaches a detector. Various compounds move at different speeds and thus separate from one another
(smaller compounds will elute faster). During this transition, the separate compounds arrive at the detector
at different times. The detector counts the fragments as they pass through and signals a recorder that prints
a graph that represents each of the compounds detected (the height of the peak corresponds to the
abundance of the substance in the sample). The graph is called a chromatograph/chromatogram. If
technicians need further information, they can combine the GC results with either mass spectroscopy or
infrared spectrophotometry results.
Images from: Imbricate hair: www.histology-world.com, Caliber: www.hunter-ed.com, Other images – Criminalistics textbook Medullas: http://www.personal.psu.edu/users/c/l/clv14/sci101/hair.htm,