Question 1

An analyst receives a small paint chip from a hit and run case. A part of testing, they obtain an FTIR of one of the layers. The spectrum will most likely reveal

Accepted Answer

FTIR analysis can reveal class characteristics of a paint, such as the type of binder, pigment, and filler used, but not specific chemical identification, manufacturer information, or vehicle information.

Question 2

A physical match of two pieces of physical evidence

Accepted Answer

A physical match of two pieces of physical evidence often provides definitive linkage of the two, meaning that they are likely from the same source. While it may not always be definitive, physical matching is a strong indication of a connection between the pieces of evidence.

Question 3

Physical characterization of a piece of trace evidence, such as plastic from a plastic trash bag, includes all of the following except

Accepted Answer

A

Question 4

Chemical characterization of a piece of trace evidence, such as plastic from a plastic trash bag, includes all of the following except

Accepted Answer

Measurement of striations in the plastic is not a chemical analysis method. It is a physical analysis method used to compare tool marks or other physical features on the plastic to potential sources. The other options listed are all chemical analysis methods used to identify and characterize the chemical makeup of the plastic.

Question 5

A green wool fiber is recovered from a blanket used to cover a homicide victim found in a shallow grave. The investigation leads to a suspect and green fibers are collected from the carpeting in the truck of the suspect's car. The analyst uses FTIR, UV-VIS, and microscopic examination to compare the two samples (Q vs K). All of the following are potential results except

Accepted Answer

Definitive proof that the fiber from the victim came from the car is not a potential result because fibers from the same source can be found in different locations, and the presence of the same fiber cannot definitively prove that it came from a specific location. However, it can be used as supportive evidence in the overall investigation.

Question 6

Which of the following is not an example of an acquired characteristic of paint on a door?

Accepted Answer

All of the listed characteristics are acquired and can change over time due to various environmental factors. Therefore, none of the options can be considered as not an example of an acquired characteristic of paint on a door.

Question 7

An analyst collects UV-VIS spectra from several locations on the surface of a tape sample. This information will aid in characterizing

Accepted Answer

UV-VIS spectroscopy is commonly used to gather information about the chemical composition of a sample. By collecting spectra from different locations on a tape sample, an analyst can determine the within-sample variation in chemical composition. This information can be used to aid in identifying different layers or coatings within the tape, as well as detecting changes in the chemical composition of the tape over time. Therefore, the best choice is A) within sample variation.

Question 8

Analysis reveals that a fragment of duct tape has two layers, a fibrous backing with a criss-cross pattern, a nylon-based adhesive, and a semi-tacky adhesive. This information arises from the process of

Accepted Answer

Successive classification involves analyzing and categorizing different components or layers of a sample, such as the fibrous backing and adhesives in the duct tape fragment.

Question 9

Successive classification can lead to which outcomes?

Accepted Answer

Successive classification involves grouping objects or individuals into categories based on certain characteristics. As more categories are added, some may be excluded or included based on the criteria used. It is also possible for some to fall into an indeterminate category. Therefore, all of the above outcomes can occur.

Question 10

An analyst performs a color test on a suspected drug sample and reports that a purple color results. This is a/an

Accepted Answer

The description of the color change to purple is subjective because it relies on the analyst's personal observation and perception of color, which can vary between individuals. Objective descriptions would involve measurable data.

Question 11

Humans have cells in the retina that are sensitive to three ranges of color which are

Accepted Answer

The three types of cells in the human retina that are sensitive to color are called cones and they are most sensitive to long (red), medium (green), and short (blue) wavelengths of light. This allows us to perceive a wide range of colors and hues.

Question 12

Color receptors in human vision correlate to _____ in the CIE system

Accepted Answer

The three types of color receptors in human vision correspond to the three primary colors in the tristimulus value system, which is used in the CIE color space. Therefore, the answer is B. LAB values represent a specific color space in which L stands for lightness, A represents the color on a green-red axis, and B represents the color on a blue-yellow axis. Hue, saturation, and depth are characteristics of color but do not correlate directly to color receptors in human vision. Observer angle refers to the position of the observer in relation to the light source and can affect color perception but is not a direct correlation to color receptors.

Question 13

The key reason for using the CIE and related systems in forensic applications is

Accepted Answer

The key reason for using the CIE and related systems in forensic applications is to remove subjectivity from color analysis. These systems provide standardized color values that can be objectively measured and compared, reducing the potential for human error or bias in interpreting colors.

Question 14

What is an additive color system?

Accepted Answer

An additive color system is one in which the primary colors (red, green, and blue) can be combined to create other colors. This is commonly used in digital displays such as TVs and computer monitors. Option A is incorrect because intensity is not necessarily tied to changes in hue in an additive color system. Option B is incorrect because changes in hue do not necessarily affect the intensity of colors. Option D is partially true, but not specific enough to be the best choice. Option E is incorrect as there is a correct answer.

Question 15

Chromaticity coordinates are used to

Accepted Answer

Chromaticity coordinates are a way to describe color in two dimensions, without including the brightness or intensity of the light. They are defined as the ratios of the three primary color components of a light source, and can be used to plot data points in a two-dimensional space known as the chromaticity diagram. This allows for easy visualization of color differences and relationships between different colors.

Question 16

The following is a spectrum in the VIS range.

If this is a reflectance spectrum, what is the best description of the color?

Accepted Answer

The answer of The following is a spectrum in the...

Question 17

The following is a spectrum in the visible range

If this is a transmittance spectrum, what is the best description of the color?

Accepted Answer

The answer of The following is a spectrum in the...

Question 18

Why are CIE LAB coordinates used more often in forensic applications than chromaticity coordinates?

Accepted Answer

The CIE LAB color space is designed to be perceptually uniform, meaning that the same amount of numerical change in these values corresponds to roughly the same amount of visually perceived change. This symmetry makes it particularly useful in forensic applications where precise color differences are important.

Question 19

What differentiates a dye from a pigment?

Accepted Answer

The key difference between a dye and a pigment lies in their solubility. Dye molecules are generally more soluble in water and other solvents than pigment molecules. Dyes tend to be smaller molecules, while pigments tend to be larger and insoluble in water.

Question 20

Why is it important to characterize several locations on a fiber or fibers?

Accepted Answer

The answer of Why is it important to characterize several...

Quiz 14: Forensic Chemistry and Trace Evidence Analysis