18-2 Firing Pin Analysis - Robert Ly | Library

Scenario
Cartridge casings were found at two different recent crime scenes. Refer to photographs labeled A–L on the following pages. Three suspects were apprehended. Police test-fired firearms belonging to the suspects and compared firing pin marks and other marks on the cartridge casings with those marks on the crime-scene spent cartridge casings.

Background
When cartridge casings are recovered from a crime scene, they are photographed and compared with National Integrated Ballistic Information Network (NIBIN) database records to determine whether they are consistent with any cartridge casings found at previous crime scenes. The NIBIN database allows investigators to link a series of crimes to the same perpetrator. Spent cartridge casings bear identifying marks, including the name of the manufacturer, caliber, ejector/extractor marks, breechblock marks, and firing pin impressions. In this activity, you will compare marks on the suspect’s spent cartridge casings with the marks on cartridge casings found at a crime scene. Include the following:
Caliber of the cartridge
Headstamp marking of the manufacturer
Location of the firing pin strike
Description of the unique firing pin characteristics

1

Caliber?
_______ 

1

Cartridge diameter?
_______ inch

1

Cartridge manufacturer?
__________

1

Centerfire of rimfire? (see show your work)
__________

0

Unique characteristics?

1

Caliber?
_______ 

1

Cartridge diameter?
_______ inch

1

Cartridge manufacturer?
__________

1

Centerfire of rimfire? (see show your work)
__________

0

Unique characteristics?

1

Caliber?
_______ 

1

Cartridge diameter?
_______ inch

1

Cartridge manufacturer?
__________

1

Centerfire of rimfire? (see show your work)
__________

0

Unique characteristics?

6

Using what you know about firing pin impressions, breechlock faces, extractor marks, and cartridge casings, match the following cartridge casings to a particular suspect's firearm.

A
B
C
D
E
F
G
H
I
J
K
L

0

Describe characteristics that were shared among all 3 suspects' cartridges. Utilize the following vocabulary words we learned: centerfire, caliber, name of manufacturer

1

Were you able to exclude any of the suspects? Select all that apply.

0

If you were a prosecuting attorney, what argument could you provide to counter the defense’s argument that “if a suspect’s cartridge shell casings were not found at a crime scene, he must be innocent”?

2

Crime labs today are better able to compare and analyze ballistic evidence. Describe two advances in technology that have allowed improved reliability of ballistic evidence.