September 29, 2014
How can footwear evidence be
used to solve crimes?
Identification of a suspect (more on this later!)
 Number of perpetrators
 Location of prints may help reconstruct crime

 Confirm / rebut alibis or witness statements
 Sequencing events
 Finding other evidence
 Tracking a suspect

Gait characteristics - how a person walks
(stride, step length, step width) may indicate
whether or not they were injured
How can footwear be
individualized?

Footwear size and brand can be easily
determined.
 This is class evidence and has limited probative
value.
 Remember:
○ Class evidence – evidence that narrows down items
to a smaller group or category (e.g. red Ford
Mustangs)
○ Probative value – ability to prove something
How can footwear be
individualized?

Footwear size and brand can be easily
determined.
 This is class evidence and has limited probative
value.

How do you think we can
individualize footprints?
 Wear patterns
 Cuts, scratches, gouges,
embedded items
Vocab Check!
Visible
 visible to the naked eye; also called patent.
 Example: print made with blood or mud
Latent
 nearly invisible to the naked eye.
 Example: print made with fine layer of oil or dirt
Plastic
 an impression in a moldable material.
 Example: print made in snow.
Obtaining Footprints

Visible prints are typically just photographed.
 Photographs should be head-on (90o angle) and
should include a small ruler. Why?
Obtaining Footprints

Latent prints must be visualized by:
 dusting with fingerprint powder or
 lifting with electrostatic lifting devices.
Electrostatic lifting devices use electricity to attract
the dust of a footprint onto special adhesive paper.
Obtaining Footprints

Plastic prints (impressions)
 First the print is photographed (why?)
 Then, a cast is made with dental stone, a hard
durable plaster.
○ Put a frame around the impression
○ Very soft impressions (e.g.
impressions in mud or
snow) are sprayed with
shellac or lacquer to
stabilize them
○ Pour the dental stone into
the impression, and allow
to set
Quick Review – Think, Pair, Share
Scholar on the left answers …
1) Name three types of information that can be
learned from footprints.
2) Describe characteristics of footprints be used to
identify a suspect.
Scholar on the right answers …
3) How is the processing of shoe prints similar to
that of fingerprints? How is it different?
Categorizing Tool Marks
Tools used during crime leave marks; some of
the marks may be used to identify the tool.
 Indentation marks –
 Occur when a tool is pressed against a soft surface
 Example: a screwdriver tip wedged into a window
seal
 It is often possible to tell the type & size of tool from
indentation marks – which type of evidence?
 It is difficult to find individualized characteristics
from indentation marks
Categorizing Tool Marks

Sliding marks –
 Occur when a tool slides or scratches across a
surface
 Example: Crowbar sliding
against window seal
 Leaves a unique pattern of
striations (lines)
 Class evidence (type of tool,
size, etc.) usually cannot be
determined
Categorizing Tool Marks

Cutting marks –
 Left behind by tools that cut through material
 Combination of indentation and sliding
 Example: wire cutters
 Often leave behind unique striations
Preserving Tool Marks
1. Tool marks are photographed
2. Casts are made of tool marks using rubberized
silicon because it retains the fine details of the
impression
3. The suspect tools are used to scrape or cut a test
surface.
4. The striations of the test surface and the evidence
are compared using a microscope.
Quick Review: Thumbs up or Down
1. It is often possible to determine the size and type
of tool used from sliding marks.
False! Indentation marks can provide this information.
2. Striations from cutting marks can sometimes be
used to determine exactly which tool was used in
a crime.
True! Both cutting and sliding marks may leave unique
striations.
3. Dental stone is used to make casts of both shoe
impressions and tool marks.
False! Dental stone is used for shoe impressions,
but rubberized silicone is used for tool marks.
Closure
What were our objectives?
Did we learn them?
How do our objectives relate to our unit
goal?
Exit Ticket
Add to your “Do Now” page
1) List 3 ways shoe impressions can be
used to solve crimes
2) Which types of tool marks are most
likely to let investigators identify the
exact tool used? Why?