Download Forensic Science Final Exam Review

Forensic Science Final Exam Review
Human Identity (Fingerprints, Forensic Anthropology, DNA)
1.Who developed the system known as anthropometry? Bertillion
2.Who postulated the exchange of evidence principle? Locard
3.In comparing footwear samples, you look for both class and individualizing characteristics. Give
examples of each. Class: tread pattern, shoe size, logo Ind: gauge/hole in sole, wear pattern
4.What are 4 factors that can be rightfully cited as an explanation for the rapid growth of crime labs
during the last 25 years?
Increase in crime rate
Supreme Court decisions during the 1960’s that resulted in fewer confessions
Increased drug use
Advent of DNA profiling
5. Which unit has the responsibility for the examination of body fluids and organs for the presence of
drugs and poisons? the toxicology unit
6.The final evaluator of forensic evidence is the jury.
7.The first rule in crime scene photography is: do not touch/move/disturb evidence unless it is in
imminent danger of being lost/destroyed
8.What factors help an investigator decide how to search a crime scene?
Size of scene, locale, type of crime, available search team, scope of scene
9. Any object that can establish that a crime has been committed or can link a crime and its victim or
perpetrator is called physical evidence.
10.Whose responsibility is it to secure the crime scene? The first responding officer
11.Why must notes be taken during the documentation of a crime scene? the investigator may be called
upon months or years later to testify and cannot rely on his or her memory alone to recall
details of the scene.
12.Hair samples, blood samples, bullets, hand swabs, etc, are all evidence that would logically found
or taken at what kinds of crime scenes? Violent crime
13.List some techniques scientists use in order to be able to visualize latent fingerprints: oblique lighting,
alternate light source, special powders, chemical reagents, superglue fuming
14. Which skeletal features are most useful in estimating skeletal age? Skull (teeth, sutures) and other
places on the skeleton where growth plates (epiphyses) fuse as the person ages
15.The skull and the pelvis are the most sexually dimorphic features of the human skeleton.
16.The analysis of skeletal remains within a legal investigation is called forensic anthropology.
17. How do male and female skeletons compare prior to puberty? They are virtually identical Which
features about the human skeleton allow us to determine gender? Skull and pelvis are most helpful,
but male skeleton is more “robust” while the female is more “gracile” Age? Sutures, dentition,
growth plates Stature length of long bones and analysis with regression formulas
18.What is “The Body Farm”? a research facility where human remains are studied as they decay in
order to gain a better understanding of decay processes and timelines
19.The cooling of the body after death is referred to as algor mortis.
20. Loops, whorls, and arches are considered to be which type of characteristic? (Class, individual, etc)
21.Under which circumstances have two people been found to have identical fingerprints? None to date
22. What is AFIS? Database for fingerprints What is CODIS? Database for DNA
23. From whom, and in what proportions, do you inherit your DNA? Half from each parent
24. Why is DNA considered to be the “gold standard” of identification? it is statistically unique and is
scientifically analyzed (there is not subjectivity about it)
25. Under what circumstances might two people have identical DNA? Identical twins
26. How is DNA analyzed (2 lab techniques that we discussed)? Traditional gel electrophoresis and
capillary gel electrophoresis
27. How is the identification of a victim, suspect, etc. different in reality from what is portrayed in TV crime
series? Not everyone is in CODIS or AFIS and the time that it takes to identify someone/solve a crime
is much longer than what is usually portrayed on television
28. What does a forensic odontologist study? Teeth What kinds of evidence might s(he) analyze? Dental
records, skeletal remains of the jaw and teeth, bite marks
29. Are crime labs infallible? No- in fact, some have been found to have corrupt individuals who have
tainted the cases on which they worked.
Trace Evidence Analysis and Identification
30. In general, hairs and fibers are difficult to individualize. Because of this, they are considered to have
mainly class characteristics.
31. The central region of a hair may contain a structure called the medulla
interrupted, or fragmented.
32.The follicle tag is the part of the hair that is most likely to contain DNA.
, which may be continuous,
33.If DNA is found from hair and is matched to a known DNA sample, then the hair is considered to have
individualizing characteristics.
34.One difference between human and animal hair is the frequent absence of the medulla in humans.
35.The outer layer of a hair is the cuticle and it is covered in scales made of keratin.
36.The natural color of a strand of hair is determined by the number and concentration of pigment granules
which are made of forms of melanin.
37.Synthetic fibers are made of large molecules called polymers which are made of smaller repeating units
called monomers. These fibers are mass produced. Why is that a problem for forensic scientists? It
increases the number of potential sources of fiber evidence
38.Give 4 examples of natural fibers. Cotton, silk, flax, hemp, asbestos What is the most common one?
cotton
39.The first 2 characteristics that a fiber expert will compare in synthetic fiber sample are
cross sectional shape and cross sectional diameter
40.One characteristic of a fiber can be that it might have two different indices of refraction. The difference
between these indices is called birefringence
41. List (in order) the three stages of hair growth. Anagen, catagen, telogen
42.This hair growth stage is characterized by rapid cellular division in the root: anagen
43. Paint evidence is often analyzed by crime labs. What value can it have? Often transferred to tools or
automobiles during crimes- can be used to associate two objects
What tools do experts use to analyze and compare paint samples? Microscopes, pyrolysis gas
chromatography
44. Soil (and other related material) is best examined by a forensic geologist
45. Soil can be useful evidence because: it can be carried into and out of crime scenes and can be
“narrowed down” to particular source areas. Also, it may contain contaminants or peculiar
materials specific to a certain location. Soil in a tire well can indicate where, and in which
order, a car has travelled.
46. What role did trace evidence play in the McDonald murder case? There were synthetic fibers that
were in question in an appeal and they were found to be consistent with the victim’s wig.
47. What famous case involved the analysis of trace metals? The Kennedy Assassination
Tools of the Forensic Scientist
48.What is one effect of the fact that light is a form of electromagnetic radiation? It can move through a
vacuum (like space)- does not require a medium (material) in order to travel.
49. What is the mathematical relationship between the frequency, wavelength, and speed of light? c=λf
50. As wavelength increases, which color end of the visible spectrum is approached (blue or red)?
51. What is refraction? When the path of light is bent as the light moves from one material to another
52.In two of your labs, you used a device called a colorimeter. This instrument could be set at different
wavelengths and was able to measure the absorbance of light by a solution. (our colorimeter
uses the visible spectrum)
53. The general relationship between absorbance and concentration is known as Beer’s law, and is what
kind of mathematical relationship? Direct (as concentration increases, absorbance also increases)
54. How would the relationship in #53 look in a graph? Linear
55. How could we use the colorimeter in a forensics lab? (What applications could it have?) toxicology
(determining concentration of poison/drug in a sample) analysis of pigment-containing
substances (like ink from a ransom note or bad check)
56. What is the name for the little containers that we used in the colorimeter? cuvettes
57. What does each of the following do: gas chromatograph, mass spectrometer, FTIR, thin layer
chromatography? For each test, indicate whether the results are definitive or presumptive.
GC: separates mixtures into constituent parts using a carrier gas; high speed and reliable, but
presumptive results
MS: analyzes substance (or parts of a substance) based on the behavior of ionized particles as
they move through a magnetic field; the results are definitive
FTIR: analyzes substances based on their infrared “fingerprint”; definitive results
TLC: inexpensive, easy, fast- separates mixtures into component parts; Rf values can be
compared to known substances; presumptive results
58. How is gas chromatography used in tandem with mass spectrometry? The parts that are separated via
GC are sent directly to MS
59. What is an analyte in a chemical testing situation? The material being analyzed
60. Differentiate between the electron microscopes, comparison microscope, stereomicroscope, compound
light microscope, and micro-spectrophotometer. (What is each “good for?”)
Electron microscopes (TEM, SEM): extremely high magnification potentials, high resolution; use
electrons instead of visible light
Comparison Microscope: side by side light microscopes connected by optical bridge; allows user
to see magnified images side by side
Stereomicroscope: upright, 3D image. Low magnifications but great for “scanning” large, bulky
items for trace evidence.
Compound light microscope: best “general tool” with variable magnification levels
Micro-spectrophotometer: instrument that is attached to a compound light microscope and
allows chemical analysis of materials as on observes them on a sample
Advanced Crime Scene Topics
61. What can investigators tell about a crime from bloodstains? (List at least 3 things)
type of event (gunshot vs. stabbing, etc), manner in which the blood fell (drip, spurt from artery,
project from object, etc), location in the space where the blood was produced, potential
identification of victim/suspect, how many blows occurred (if blunt force trauma), where a
missing object/person was with respect to the victim (if there is a “void” in the cast of or blow
back spatter)
62. How does the shape of a blood stain change as the angle of impact increases (from zero to 90 degrees)?
The closer to 90 degrees, the more circular the stain
63. Bloodstains that are created when the force acting on the blood is gravity are called passive
64. The smaller the size of the droplets in a spray of blood spatter, the: higher the velocity at which they
were moving
65. How do experts determine the angle of impact of a bloodstain? 1. Measure length (not counting
satellites or tails) and length of stain 2. Divide width by length 3. Take the inverse sine of the
result
66. How do experts determine where in a space (such as a room) a blood spatter-producing event occurred?
1. back trace each stain to find the area(s) of convergence
2. measure the distance of each stain from the center of its area of convergence
3. determine the angle of impact
4. multiply the tangent of the impact angle by the distance
5. stains that have results within about a foot of one another probably came from the same event
67. How can an expert tell which way a blood drop was traveling before it hit a surface? The tail points in
the direction it was travelling.
68. Be able to calculate angle of impact, find areas of convergence, etc.
69. How do investigators find blood evidence that is not visible to the naked eye? (More than one test)
Luminol and Kastle Meyer
70. Are the test that you listed in #69 presumptive or confirmatory? Explain. Other materials (besides
blood) can produce positive results with each of these.
71. What is PMI, and how are insects used to estimate it? Post Mortem Interval (time since death); flies
lay eggs right away on a corpse and the larvae mature at specific rates depending on the species
and the environmental temperature.
72. What factors affect the ability of adult flies to find a corpse and lay eggs on it? Flies usually won’t fly
in the rain (especially storms); if a body is tightly wrapped it will take them longer to find it and
get to it. If a body is buried it will delay the flies.
73. The air temperature of the surroundings of a body is called the ambient temperature.
Firearms and ammunition identification
74. Any mark made in a softer surface by a harder implement is called a tool mark.
75. The purpose of the rifling in a barrel is to: make the bullet spin, which allows it to maintain its path.
74. The rifling lands leave deep marks in a bullet as it travels through the barrel, and the grooves leave
raised areas on the bullet. Within these impressions are microscopic scratches called striations. These
are unique to the firearm, so they are considered to have individualizing characteristics.
Miscellaneous Diagrams
75. (Fingerprint pattern chart)
Name of Pattern
Arch
whorl
Loop
Incidence In US
(most common/least Least common
Most common
common)
Description of ridge Start at one side and Enclose upon
Start and leave on
lines
leave on the other themselves in
the same side
circular patterns
Deltas (absent, one, Absent
At least 2
1
two)
Sub-types
Plain and tented
Double loop, pocket Ulnar and radial
loop, accidental
76. Label the hair diagrams:
77. Be able to determine Rf values from
a TLC plate (diagram)
abcdef-
shaft
root
follicle
cuticle
e- medulla
f- cortex
78. Be able to label the parts of a compound
light microscope.
79. Be able to recognize a human hair vs
an animal hair
80. Be able to recognize characteristics of female skeletal parts vs male
81. Be able to identify the following structures/features of a human skeleton (may not be the
same diagrams, and you do need to know the major skull features that we learned- ie: occipital
protuberance, nasal spine, zygomatic bone):