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Toolmark Examinations

Tools can be used in the commission of crimes.  They can aid criminals in gaining entry or damaging property.  When the tools are used, they can leave behind unique marks on the surfaces they contact.  Law enforcement agencies will submit tools and the items bearing toolmarks to the BCA.  Examiners in the Firearms and Toolmarks Section can help solve a crime by identifying a toolmark to a particular tool.
Toolmark on DoorMagnified Toolmark on Door

Test Toolmark in LeadToolmark Examiners evaluate tools to determine that they are capable of producing the questioned mark.  They will then use the tool to make test toolmarks, usually in soft lead.
 
 
 
 
 
 
 

 

  

Cast of Test Toolmark
 
Silicone-based casting materials are useful for capturing marks on items that are too large to transport to the BCA or to fit under a microscope.  The examiner will also cast the test toolmark for comparison.
 
 
 
 
 
 
Comparison of Casts of Toolmarks
 
Similar to bullets and cartridge cases, the examiner will conduct comparative examinations on toolmarks using the comparison microscope.  The toolmark examiner will compare the small unique features of the test mark and the toolmark on the evidence.
 
 
 
 
 
 
 
If the marks “match”, the examiner can determine that the tool used to create the test toolmark also made the mark on the evidence item.