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Ballistics and Impression Evidence Test
Terms in this set (36)
1. What is the goal of toolmark and firearm examination?
Tool marks can be linked to tools used at a crime scene, and ultimately may be used to help find the suspect who used it. Firearm examination has the goal of trying to link a gun to a crime and place a suspect at the scene.
2. What were the first firearms and how did they ignite? Which came first?
First firearm was a cannon, which was a tube with some gunpowder in one end that had a fuse coming out and then plugged with a cannonball. When the fuse was lit, the gunpowder exploded, causing the ball to shoot out.
First guns were called muzzle-loading matchlocks that used wicks to ignite the gunpowder and send a bullet out just like a cannon
3. What is a cartridge?
A case that holds a bullet, prime powder, and gunpowder.
4. What is the function of the primer? How is it ignited?
Ignites the propellant (gunpowder) when struck
5. Who invented gunpowder and for what purpose(s)?
Gunpowder was invented over 1000 years ago by the Chinese - to make weapons (and fireworks)?
6. How does gunpowder work?
Provides chemical energy which pushes the bullet out of the cartridge.
7. Explain how the firing action of a gun works.
When the trigger is pulled, the firing pin hits the base of the cartridge, igniting the primer powder. This causes a spark that makes the gunpowder explode, forcing the bullet down the path of least resistance (the barrel). The bullet follows the lands and grooves in the barrel, which causes it to come out spinning.
8. Using correct terminology, explain how different parts of a gun and cartridge enable the bullet to be fired from a gun.
9. What are class and individual characteristics? Give two examples of each.
Class: The number of lands and grooves and the width and direction of twist
Individual: Striations and groove impressions
10. What is the most useful tool in firearm and tool mark examination?
Comparison microscope, because it allows investigators to examine two different things in the same field of view.
11. What is rifling? What purpose does it serve?
A unique pattern left on the bullet- the bullet spins through the air to improve accuracy.
12. What are lands and grooves?
Lands are the raised portion between the grooves, and the grooves are the cut or low-lying portions between the lands in a rifled bore.
13. What are striations?
Individual characteristics of the barrel - the inner surface of the barrel leaves its striation markings on a bullet passing through it
14. Besides rifling, what other unique patterns can help match a bullet to a weapon?
Breech marks, firing pin impressions, and extractor/ejector marks.
15. How is the caliber of a firearm measured?
The measure of the diameter of the cartridge, measured in hundredths of an inch.
16. What is the difference between a shotgun and a rifle?
Shotguns fire pellets or slugs and the interior is smooth, while rifles fire bullets and the interior is rifled
17. Label the following:
Different types of weapons (round nose, hollow point, wadcutter)
18. How should a gun found in water be collected and transported?
In the water that it was found in (to avoid rust)
19. What does GSR stand for?
20. How can someone determine the distance a gun was from the target at the time of fire? Be specific.
GSR patterns (Contact, close, intermediate, distant)
21. What is trajectory?
The path of the projectile after it leaves the gun
22. What information is needed to calculate trajectory?
A. Horizontal distance between victim and shooter
B. The height of the building above the wound (location of shooter)
C. Draw a picture of what this situation might look like
23. Why might a bullet's path be slightly curved?
Over a long distance, gravity and air resistance may make the bullet have a slight downward curve.
24. How does the size of an entrance wound differ from the size of an exit wound? Explain why.
Entrance wounds are usually smaller - when the round is in the body, it slows down, and therefore it has to force harder to push through.
25. What is the acronym for the national ballistics database?
NIBIN (National Integrated Ballistic Information Network)
26. How can toolmarks be linked to tools used at a crime scene?
1. Certain defects or patterns may be left on a tool when it is made or used over time
2. Tools may oxidize or rust making them more unique
3. Tools often come with serial numbers as well. - even ones that have been rubbed off can often be recovered
27. What are the 3 types of tool marks? How are each created?
1. Indentations: made by a tool when it is pressed against a softer surface, often forming a negative impression on the object receiving the force
2. Abrasion: When surfaces slide across one another
3. Cutting: Produced along the edge as a surface is cut
28. At what type of crime scene are tool marks most often encountered?
29. What class characteristics do all shoes possess?
Size, brand, and design/patterns
30. Explain the steps you would take to document and preserve a shoe impression found in a flower bed at a crime scene.
3-D impressions are able to be preserved using Plaster of Paris which fills in the print and produces a cast
31. What should an investigator do if they encounter a bloody footprint?
Photograph the bloody footprint.
32. What information do investigators collect from tire tracks/impressions to help them identify a vehicle? Be specific.
Track widths, wheelbase lengths, and turning diameter and check them against a vehicle database.
33. Classify each of the following characteristics as class or individual: Tread pattern, an abrasion on the surface of the tread, shoe size
Tread pattern: Class
Abrasion on the surface of the tread: Individual
Shoe size: Class
34. Why are teeth one of the most distinct and longest-lasting features of mammals?
Teeth are not made of bone; instead the hard white portion of a tooth is enamel and dentin (enamel is the hardest substance in the human body)
35. How can teeth be used to estimate age?
Because permanent teeth develop at different rates, teeth can be used to determine a rough estimate of a person's age (32 adult teeth, __ child teeth)
*Summarize court cases that were presented in class.
Richard Ramirez- The Night Stalker: Serial killer who used .22-caliber - Avia aerobic shoe print
Ted Bundy- Serial murderer, rapist, and necrophiliac- caught with odontology
JFK- Shot by Lee Harvey Oswald, and was caught with film ballistic evidence
Hernandez- Ballistics+impressions (tire treads and shoe prints)
O.J Simpson- Mainly caught due to shoeprints
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