Preview

1
Preview

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

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?
• Chapter 15

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Firearms Identification

• A forensic science often referred to as
  ballistics. Forensic ballistics identifies
  firearm usage in crimes.
• Its 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

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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.

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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.

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1. Comparison of Impressions on Two Cartridges.
2. Comparison macroscope.3. Bullet from the
Kennedy assassination.
10
Review

1. What is firearm identification?
2. Why is firearm identification also considered a
   branch of tool mark identification?
3. How is firearm ID like fingerprint ID?
4. 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.
• http//www.firearmsid.com/Bullets/bullet1.htm

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Bullet Identification

• Located within the rifling impressions on a
  bullet can be microscopic striations or scratches
  like those seen on the bullet below.   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.

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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.

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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
  1990s)
• 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 1990s).
• Digitized microscopic images of identifying
  features found on both spent bullets cartridge
  casings.
• Drugfire IBIS was incompatible systems that
  posed problems w/ local officials.
• 3. 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

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GSR Tests

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

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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.