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2.  The term ballistics refers to the science of the travel of a projectile in flight.  The flight path of a bullet includes: travel down the barrel, path through the air and path through a target 2

3.  Forensic ballistics is the science of analyzing firearm usage in crimes.  Forensic ballistics involves analysis of bullets and bullet impacts to determine the type.  Separately from the ballistics information, firearm and tool mark examinations also involve analyzing firearm, ammunition, and tool mark evidence in order to establish whether a certain firearm or tool was used in the commission of a crime. 3

4.  One of the disciplines of forensic science is firearms identification which is defined by forensic experts as: The identification of fired bullets, cartridge cases or other ammunition components as having been fired from a specific firearm. 4

5.  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. 5

6.  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. 6

7.  Another aspect that people often don’t know, is that 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. 7

8.  Most law enforcement agencies have access to a forensic laboratory to aid in their investigations where highly skilled forensic experts conduct examinations on many different types of evidence collected at crime scenes, including on firearms, bullets and cartridge cases. 8

9.  Firearms evidence submitted to a lab's Firearms Section will typically include:  a firearm  spent bullets  spent cartridge cases  spent shot shells and/or shot  shot shell wadding  live ammunition  clothing 9

10.  Forensic ballistic experts 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. 10

11.  Cartridges and cartridge cases on the other hand are examined for similarities in what are called breech marks, firing pin impressions, extractor marks, ejector marks and other named toolmarks. 11

12.  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. 12

13.  If the firearm is not recovered, and the crime lab has the marks on a cartridge case there's yet another approach.  They can input it into one of the many databases – similar to CODIS, the DNA database.  One of the ballistics databases forensic labs in the USA use is FBI sponsored Drugfire. 13

14.  The Firearms-Toolmark Unit (FTU) is one of many subdivisions of the FBI Laboratory devoted to a specific discipline of forensic science.  They use Drugfire, an automated, national computerized forensic firearms identification system that integrates, cartridge case, shotshell and bullet analysis, as well as electronic firearms reference libraries, on a single computer platform. 14

15.  Hits are made when a system user finds a match between a specimen they added into the database and a previously filed specimen. 15