1-9 Impressions made by tools
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1 CASTS AND IMPRESSIONS
Each tool has its own characteristics
Tool marks can include impressions from a screwdriver, chisel or jemmy, cut marks made by wire
cutters or a saw, or scratch marks that could be made by a knife or other sharp instrument scraping
over a surface.
These marks can provide much information to an
experienced investigator, and can possibly lead to the
identification of the implement that made them, and
hence link a possible suspect to the crime scene.
A tool mark that is commonly found at a forced
entry, is that caused when a tyre lever,
jemmy, chisel, screwdriver, or other easily
accessible tool, is wedged between a
wooden door jamb and a door, or between
a window and its frame. The much harder
metal compresses the wood, leaving an
impression of its shape behind.
Notice in the diagram below how the small nicks and breaks on the end of the screwdriver match
the impression. This individualises the tool to that particular mark.
Matching a tool mark to a tool A cast made of a tool mark left by a chisel
Other screwdrivers of the same type would not be expected to have exactly the same little nicks in
exactly the same places and be of exactly the same shape. Most metal tools acquire their own unique
individual marks through general wear and tear. It is these marks that can link one particular tool
with a crime scene or to an owner. If matching marks cannot be found on a suspect's own tools then
it may actually help in proving innocence.
18 © John Powrie and Jeannette Jolley and Learning Essentials 2003. This page may be photocopied for non-commercial classroom use.
0
1 CASTS AND IMPRESSIONS
Each tool has its own characteristics
Tool marks can include impressions from a screwdriver, chisel or jemmy, cut marks made by wire
cutters or a saw, or scratch marks that could be made by a knife or other sharp instrument scraping
over a surface.
These marks can provide much information to an
experienced investigator, and can possibly lead to the
identification of the implement that made them, and
hence link a possible suspect to the crime scene.
A tool mark that is commonly found at a forced
entry, is that caused when a tyre lever,
jemmy, chisel, screwdriver, or other easily
accessible tool, is wedged between a
wooden door jamb and a door, or between
a window and its frame. The much harder
metal compresses the wood, leaving an
impression of its shape behind.
Notice in the diagram below how the small nicks and breaks on the end of the screwdriver match
the impression. This individualises the tool to that particular mark.
Matching a tool mark to a tool A cast made of a tool mark left by a chisel
Other screwdrivers of the same type would not be expected to have exactly the same little nicks in
exactly the same places and be of exactly the same shape. Most metal tools acquire their own unique
individual marks through general wear and tear. It is these marks that can link one particular tool
with a crime scene or to an owner. If matching marks cannot be found on a suspect's own tools then
it may actually help in proving innocence.
18 © John Powrie and Jeannette Jolley and Learning Essentials 2003. This page may be photocopied for non-commercial classroom use.
