1. Preview What is firearm identification?
Why is firearm identification also considered a branch of tool mark identification?
How is firearm ID like fingerprint ID?
List 5 different types of firearm evidences examined in the lab. 1

2. Firearms
SFS4 Students evaluate the role of ballistics, tool marks and arson in forensic investigation.
a. Identify firearm lab tests used to distinguish the characteristics of ballistics and cartridge cases.
b. Analyze the physics of ballistic trajectory to predict range of firing.

3. EQ
How is firearm investigation used as a tool in crime scene investigations?

4. Firearms Identification
A forensic science often referred to as ‘ballistics’. Forensic ballistics identifies firearm usage in crimes.
It’s the identification of fired bullets, cartridge cases or other ammunition components as having been fired from a specific firearm.
It involves analysis of bullets and bullet impacts to determine the type.

5. Firearms Produce Unique Toolmarks
Firearm identification is also one of the branches of toolmark identification. This is because the firearm, made of a material harder than the ammunition components, acts as a tool that leaves impressed or striated marks on the various shell casings and other ammunition components with which it comes into contact.
And like fingerprints, no two firearms, even those of the same make and model, will produce the same marks on fired bullets and cartridge cases. Furthermore, the manufacturing processes and the use of the firearm leave surface characteristics that cannot be exactly reproduced in any other firearm. This means that the toolmarks are unique to each firearm.
Firearms do not normally change much over time. This allows for firearms recovered months or even years after a shooting to be identified by forensic experts as having fired a specific bullet or cartridge case. So, is firearm identification an individual or class characteristic?

6. Firearm Evidence Submitted to Forensic Laboratories
spent (used) bullets
spent cartridge cases
spent shot shells and/or shot
shot shell wadding
live ammunition
Clothing (may contain GSR)
Examples of firearm evidence:

7. Firearm Evidence Submitted to Forensic Laboratories
In addition to comparing ammunition components to firearms, firearm examiners conduct other examinations that usually include the following:
Testing firearms to determine if they function properly.
Examine clothing and other items for gunshot residues and/or shot patterns in an attempt to determine a muzzle-to-garment distance.
Determine caliber and manufacturer of ammunition components.  Including the examination of various shotshell components.
Determine the manufacturer or manufacturers of firearms that may have fired a particular bullet or cartridge case.

8. What do Forensic Ballistic Experts Do?
Look at certain characteristics of firearms that relate to the bullets fired from them including the caliber of the firearm and the rifling pattern contained in the barrel of the firearm.
Cartridges & cartridge cases are examined for similarities in what are called breech marks, firing pin impressions, extractor marks, ejector marks and other named toolmarks.
One of the most important tools in forensic ballistics is the comparison microscope also called a comparison macroscope, where these toolmarks can be compared side by side and matched or eliminated.

9. 1. Comparison of Impressions on Two Cartridges. 2
1. Comparison of Impressions on Two Cartridges. 2. Comparison macroscope. 3. Bullet from the Kennedy assassination.

10. Review What is firearm identification?
Why is firearm identification also considered a branch of tool mark identification?
How is firearm ID like fingerprint ID?
List 5 different types of firearm evidences examined in the lab.

11. Part II: Bullet Identification
Bullets collected for comparison to a specific firearm are examined first to see if they are of a caliber that could have been fired from the submitted firearm. 
They are then examined to determine if the pattern of rifling impressions found on the bullet match the pattern of rifling contained in the barrel of the questioned firearm. 
If these class characteristics agree the next step is to try to make a positive match between the individual characteristics that may have transferred to the bullet from the barrel.

12. Bullet Identification
Located within the rifling impressions on a bullet can be microscopic striations or scratches like those seen on this bullet.   They sort of look like a bar code.
Imperfections in the surface of the interior of the barrel leave striations on the projectiles.  Striations have the potential to be consistently reproduced in a unique pattern on every bullet that passes down the barrel of a firearm.  The key word is unique.

13. Definitions Bore-the interior of a firearm barrel.
Caliber- the diameter of the bore of the rifled firearm, usually expressed in hundredths of an inch or millimeters (mm), i.e. .22 caliber or 9 mm.
Grooves- the cut or low-lying portions btwn the lands in a rifled bore.
Lands- the raised portion between the grooves .
Rifling- the spiral grooves formed in the bore of a firearm barrel that impart spin to the projectile when it is fired.

14. Problems
Few evidence bullets are submitted intact.  Most are badly distorted, wiped and/or fragmented. 
Even small fragments and badly damaged bullets can still retain sufficient marks for an identification to be made.

15. Results from Comparisons (Example)
When comparisons are made between firearms and fired ammunition the results can read as follows:
Exhibit 1 (bullet) was identified as having been fired from Exhibit 2 (revolver).
This conclusion is reached after all class characteristics agree and a sufficient correlation between individual characteristics is found.
Exhibit 1 (bullet) could neither be identified nor eliminated as having been fired from Exhibit 2 (revolver). All comparisons were inconclusive.
This conclusion is reached if class characteristics agree but there is an insufficient correlation between individual characteristics.
Exhibit 1 (bullet) was not fired from Exhibit 2 (revolver).
This conclusion is reached if class characteristics disagree.

16. Automated Firearms Search Systems
“Drugfire”-system developed by the FBI. (early 1990’s)
an automated, national computerized forensic firearms database identification system that integrates cartridge case, shotshell and bullet analysis, as well as electronic firearms reference libraries, on a single computer platform.
Hits are made when a system user finds a match between a specimen they added into the database and a previously filed specimen.
IBIS- Integrated Ballistic identification System. Developed by the Bureau of Alcohol, Tobacco, Firearms & Explosives (ATF). (early 1990’s).
Digitized microscopic images of identifying features found on both spent bullets & cartridge casings.
Drugfire & IBIS was incompatible systems that posed problems w/ local officials.
NIBIN- National Integrated Ballistics Information Network.
Created in 1999 by a joint effort by the FBI & ATF.
A compatible system that incorporates both Drugfire & IBIS software identification systems.

17. GSR
The distribution of gunpowder particles & other gun discharge residues around the bullet holes permits a distance determination.
distance determination- the process of determining the distance between the firearm & the target.
When might distance determination be useful in an investigation?
During a claim of self defense.
Suspicious suicide/ self-inflicted wounds

18. GSR Tests
Greiss Test-A chemical test used to develop patterns of GSR around bullet holes.
Test for nitrates formed from the incomplete combustion of nitrocellulose (gun powder).
Lead test-
Test for trace amounts of lead residue around a bullet hole.

19. Examining GSR on Suspect Hand
Firing a weapon propels residues toward the target & blows gunpowder & primer residue back toward the shooter.
Traces of these residues are deposited on the firing hand of the shooter, providing valuable information as to whether a person has recently fired a gun.
Examiners swab the hand and measure the amt of barium (Ba) & antimony (Sb) present; or examine the morphology of the GSR particles containing these elements.

20. Preserving Evidence
Criminalists(Forensic Scientists) can restore serial numbers that have been removed or scratched off.
The metal stamp that are fixed into the gun and leaves a permanent imprint that can be restored.
The weapon must be tagged, properly contained and transported to the lab w/o disturbing the integrity of evidence.