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Study Guide Worksheet for Fabric Identification and Firearms IdentificationForensic Science
Mrs. Ashley
Name ______________________________________________________
Please complete the questions. This worksheet will help you in preparing for the unit test on Friday, January 17. This worksheet is due Tuesday, January 14. You will receive and answer key on January 14 to help you in studying for the test. (As a result of your receiving the answer key, this assignment will not be accepted after Tuesday, January 14.)
FIBER IDENTIFICATION1. Name three natural fibers.
a.
b.
c.
2. What are four fibers that are man-made?
a
b
c.
d
3. When examining fibers microscopically, what are three characteristics that forensic scientists would use to distinguish fibers?
a.
b.
c.
4. Sometimes forensic scientist have a fiber only and at other times they also have a piece of cloth. When they have a piece of cloth, what would they use to match the cloth that is different from a fiber only?
a.
b.
Look at the drawings below and answer the questions about these fibers:
5. Which of the fibers above are considered natural fibers?
6. Which fibers are also considered hair evidence? From the drawing, what characteristic does the hair evidence have that is lacking in fibers?
7. What are three methods for collecting fiber evidence?
a
b
c
8. Sometimes it is possible to find evidence that is more than class characteristics in fiber identification, where individual characteristics can be matched. Please explain an example.
9. What is meant by fabric impressions?
FIREARMS IDENTIFICATION
The softer metal used in the cartridge case construction may show tool marks caused by the interior chamber and action surfaces coming in contact with the cartridge case. The action is the firearm’s loading and firing mechanism. The firearm is made up of a number of tools, many of which come into contact with, and leave tool marks on the softer metal of the cartridge case and/or bullet. The firearm, as with any other tool, has features that were designed by the factory. Features that are determined by the manufacturer include the size of the cartridge chambered by the firearm, the orientation of the extractor and ejector, and the number, width and twist direction of the land and grooves of the barrel rifling. These characteristics can be imparted as tool marks on the fired bullet and case during firing, and can be classified by their class characteristics. These class characteristics are typically the first classification of tool mark evidence that the examiner seeks in the examination.
10. The picture above is an example of what kind of firearm identification?
11. Please learn the parts of the rifle below: Muzzle, barrel, stock, safety, bolt, chamber, trigger, bolt handle, and trigger guard.
12. Which part of the rifle above would be important in matching the bullet that was fired from this rifle?
13. Here is a photograph of a center fire cartridge:
14. Please learn the parts of the bullet below: Projectile (bullet); casing, powder, and primer
15. Study the picture below. Draw lines on the rifling pattern to show you know where it is located.
16. The above picture shows the firing pin impressions comparison. Draw circles around the parts of the firing pin impressions that show a match.
17. If the class characteristics agree in every respect with the evidence item (i.e., the cartridge case or the recovered bullet) and with the test-fires from a suspect firearm, the examiner then uses the comparison microscope to compare the individual characteristics of both evidence and test tool marks. Individual characteristics are random in nature, usually arising from the tool working surface incidental to manufacture, but can also be the result of use, wear, and possible care and/or abuse of the tool.
Tool marks generally appear in two forms: striated and impressed. Striated tool marks are formed when a tool-working surface is placed on another surface and moved parallel to that surface. In other words, a tool makes a scratch or scrape mark on the surface of another object. The detail in this tool mark has the appearance of parallel lines, called stria. Under the microscope the stria are seen as a profile consisting of hills, valleys and ridges. If the stria is very shallow, the tool mark appears as a pattern of lines.
In the picture on the next page draw circles around the striated tool marks that show a match.
When the firing pin or striker impacts the cartridge primer, it leaves an impressed tool mark on the soft metal of the primer, and any microscopic imperfections on the surface of the firing pin can be transferred onto the primer. These tool marks are usually individual in nature and can be reproduced during firings.
18. In the picture below of firing pin impressions draw marks that show at least three places where the two firing pin impressions match.
19. What are three class characteristics of firearms identification?
a.
b
c.
20. Complete the definitions for the following terms:
a. barrel:
b. breech:
c. bullet:
d. caliber:
e. cartridge:
f. fully automatic
g. gunshot residue (GSR):
h. impressed action marks
i. lands and grooves:
j. muzzle:
k. revolver:
l. rifle:
m. riffling:
n. shell casing:
