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READ: Arson, Firearms and Toolmarks

Introduction

Introduction

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Firearms and tools are manufactured and used in such a way that subtle variations can exist. These subtle differences enable investigators to link weapons and tools to a particular crime and sometimes even a suspect. Investigators can also study the trajectory of a projectile to gain more insight into the way in which the crime occurred. While arson fires and explosives are both destructive, they can still leave behind valuable evidence. This evidence can be used to reconstruct the crime as well as trace and connect materials of evidence to the suspect. Tool marks are often left in crimes such as burglary when a suspect attempts to gain entry into a secured location. These tool marks can indicate not only the type of tool used, but also a specific weapon if it has surface irregularities that can be matched to the observed tool markings.

 

Essential Questions

  1. How can a weapon be linked to a crime or individual?

  2. How are tool marks analyzed?

  3. What do investigators look for to determine if a fire was accidental or arson?

  4. How are explosives classified?

Module Minute

mm iconFirearms, toolmarks and arson can yield significant forensic evidence to the observant investigator. Often the evidence is subtle and requires experts within that area of specialty to adequately interpret the results of testing. Bullet casings found at a crime scene, for example, can be linked to an individual gun by comparing the firing pin marks and marks from the gun's rifling on the cartridges using a comparison microscope. At a fire scene, fire patterns can be linked to various accelerants which can distinguish an accidental or natural fire from an arson. Toolmarks can be cast just as other prints such as shoe prints can be cast at the crime scene. Often, a silicone based material is used to obtain an exact casting of the toolmarks. That casting can then be compared to known marks of various tools to identify the tool used.

Georgia Virtual, Firearms, Ballistics, Toolmarks, and Arson, CC BY-NC-SA 3.0