Forensics trace evidence test Flashcards
Which of the following is not a layer of the hair shaft?
follicle
The layers of the hair shaft are the _____________, the ____________, and the _____________.
cuticle, cortex, medulla
Which part of the hair shaft is most resistant to chemical decomposition?
Cuticle
Which feature of hair is MOST important in making a species identification?
Scale Pattern
The number of hair scales pointing towards the tip of the hair is __________ the number of hair scales pointing towards the hair follicle.
greater than
A cast of a hair surface can be made using:
clear nail polish, softened vinyl
Pigment granules that impart hair with color are found in the
The cortex
The central canal running through many hairs is known as the
Medulla
The medullary index of human hair is ___________ the medullary index for most other animals.
Less than
Medullae may be classified as being
all of the above
A hair sample was examined and its medulla appeared to have a pattern described as resembling a string of pearls. It was most likely from a
Cat
In making hair evaluations, it is best to view the hairs using a ___________ microscope.
Comparison
Microscopic hair comparisons must be regarded by police and courts as:
Presumptive
In what stage can a hair most readily be removed from the scalp?
Telegenic
The rate of human hair growth per month is:
1 cm
Beard hairs are coarse and normally ________ in cross-section.
triangular
A human hair in cross-section appeared flat in shape. The ancestral origin was most likely
African
In determining whether a hair sample originated from a male or a female, the MOST important consideration is
the results of DNA analysis performed on the root structure.
The presence of sheath cells on hair that has been pulled quickly from the head is ________ the presence of sheath cells on hairs that have been removed slowly from the scalp.
Greater than
The stages of hair growth include all of the following EXCEPT
Analgesic
Nuclear DNA typing can be most successfully accomplished on hairs that have been removed during which stage of growth?
Anagenic
The conviction of Ennis Cosby’s killer was aided by the DNA analysis on a hair that was crucial evidence in the case. This hair
belonged to the killer and was found in his cap with which he had wrapped the murder weapon before discarding it.
Before the 20th century, all fibers were
natural
Which type of crime is LEAST likely to be solved with the use of fiber evidence?
Bombing
Mohair and cashmere are hairs from:
Goat
By far the most prevalent plant fiber is:
Cotton
A fiber whose microscopic appearance includes being ribbon-like in shape (flat) with twists at irregular intervals is
cotton
What was the first man-made fiber?
Rayon
A regenerated fiber can be derived from
Acetate
Which is NOT a manufactured fiber?
all of the above
Which is made of natural polymers?
sand
The monomers involved in the synthesis of proteins are:
Amino Acids
Cellulose is the basic component of
Wood
It is a virtual certainty that two fabrics share a common origin if their fibers
Can be fitted together at their torn edges
Wayne Williams was convicted of serial murder mainly on the strength of
fiber evidence
Which of the following properties should NOT be examined when comparing two synthetic fibers?
Medullary index
The visible light microspectrophotometer is a convenient tool with which to compare the color of fibers because
All of the above
Synthetic fibers display __________ because they are crystalline
Birefringence
Generally, the parallel refractive index of a fiber is __________ the perpendicular refractive index of the same fiber.
Greater than
During the collection of fiber evidence, great care should be taken to
avoid cross-contamination of evidence
What type of evidence would be expected to have trace elements?
All of the above
The knowledge that elements selectively _______ and ________ light provides the basis for important analytical techniques designed to detect the presence of elements in materials.
absorb, emit
A _________ shows distinct frequencies or wavelengths of light.
line spectrum
In a simple emission spectrograph, excitation of the specimen under investigation is accomplished with a(n):
electrical arc
The nucleus of an atom contains:
Protons and neutrons
Atoms having the same atomic number but different atomic masses are called
isotopes
Which type of radiation is NOT given off by radioactive decay?
x-rays
Beta particles are identical to
electrons
Neutron activation analysis involves bombarding specimens with neutrons and then measuring the resultant
Gamma rays
Which of the following is a nondestructive technique for identifying and quantifying trace elements in a test sample?
Neutron activation analysis
Paint as physical evidence is most frequently encountered in
A & B
Which is NOT part of the composition of paint?
adhesive
Which property imparts paint with its most distinctive forensic characteristics?
color layer sequence
Paint binders can be chemically analyzed using:
B & C
Pyrolysis gas chromatography is a particularly valuable technique for characterizing paint’s:
Binder
The elements that comprise the inorganic pigments of paint can be identified by
all of the above
An element is selective in the frequency of light it will absorb. This selectivity is due to its
electron energy levels
After examining small paint chips from an auto accident scene and using the PDQ database, the crime lab worker can determine the __________ of the vehicle.
All of the above
What is the logical first step in soil analysis?
examination for presence of debris under low-power magnification
In most cases, the _________ layer(s) of soil is/are picked up during the commission of a crime.
top
Which would be LEAST useful in identifying a mineral crystal?
Color
Soil found on the suspect, such as that adhering to a show or garments, ____________ be removed.
Must not
During the investigation after the assassination of President Kennedy, elemental analysis of the silver and antimony content classified the bullets and fragments recovered (6 in total) into ________ distinctly different groups
2
Most soils can be differentiated by its
gross appearance
Crime labs are often asked to identify the make and model of a car from a small amount of paint and will make use of color charts for automobile finishes for the __________ database.
PDQ
Many manufactured products and even most natural materials contain small quantities of elements, known as trace elements, present in concentration of ________________.
Less than 1%
Forensic analysis has employed neutron activation on trace elements found in
metals, drugs, paint, soil, hair, and gunpowder residue
Minerals in soil can be characterized by their (select all that apply)
All of the above
Paint chips are most likely found on or near persons or objects involved in
Hit and runs
In most cases, only the top layer of soil is picked up during the commission of a crime, so standard samples should be removed from the surface - only about ____________ is sufficient.
1 tablespoon
