1 chapter 18 forensic footwear evidence. 2 what information can you gather from this foot?
TRANSCRIPT
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Chapter 18
Forensic Footwear Evidence
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What information can you gather from this foot?
What is Forensic Footwear Evidence?
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Physical contact between footwear and a viable surface leaves a transfer of class and individual characteristics, which can be used in identification of possible suspects
Forms of Footwear Impressions
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Two Forms
Three Dimension
al Impression
s
Two Dimension
al Impression
s
=Those that remain after a shoe has permanently deformed a surface.
=Those patent or
latent prints left on a
non-giving surface.
Forms of Footwear Impressions
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Sand
Mud
SnowThree D
imensional Im
pressions
Wood/PaperGlass
CarpetTwo D
imensional Im
pressions
Note: Very often the less visible
impressions actually retain greater detail
than those that result from heavier deposits
of residue, dust, or blood.
Information from Footwear Impressions
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1• Positive ID of
footwear
2• Elimination of
Footwear
3• Location of
Impressions and association with other evidence
4• Rebuttal or
Confirmation of a suspect’s alibis
5• Determination of
shoe brand/manufacturer
--Proving a suspect’s presence at a crime and thus possible participation in the crime
--Aided by use of FBI footwear database that includes thousands of shoe designs
--Based on CLASS characteristics . . .. changes in or absence of random individual characteristics are normally not used to eliminate a shoe
--Can help lead to uncovering other impressions or physical evidence
Information from Footwear Impressions
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6Determination of shoe size
7• Gait
characteristics
8• Linking of
crime scenes
9• Number of
perpetrators
10• Tracking
--Recording dimen-sions of impressions can allow for general estimate of shoe size
--Refers to how someone walks--Measurements from impressions include stride, step width, and walking pace--Note: not reliably used as a means of personal ID
-- More than one print design found can suggest the # of people who potentially committed the crime
--Databases can store footwear impressions recovered from scenes and can be used to find a matches or links between different crimes (helpful with repetitive crimes like burglaries)
--Observing impression series that can result in following the path of an individual (ex illegal aliens and kidnapped children)
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Number of perpetrator
s?
Identification of
Footwear ?
Association with
Other Evidence
Determination of Shoe
Size
Tracking
Video Duration~1:28
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Location and Recovery of Footwear Impressions
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• 1. CS Security:• Important to secure crime scenes as soon
as possible to prevent other impressions being tracked over the evidence
• 2. Location:• Some impressions easily located (i.e. bloody
or muddy)• Most require more effort to locate• Use alternative light source or electrostatic
lifting device• Use clues in environment as a place to look (i.e.
entrance and exit points, and paper, magazines, or glass on floor which often hold latent prints in good detail)
• 3. Recovery• next slide
http://www.knoxandassociates.com/photo.php
Recovery (cont.)
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Starts with notes and photographs (# cards in photo)
Take mobile prints to lab
• Prints that cannot be moved and may need to be enhanced. • 1. Examination quality photography
• directly over print, 35 mm film, ruler in picture
• oblique/UV/infrared lighting for contrast• possible use of chemicals to enhance
before photo (ex. leuco crystal violet, amido 10 black, luminal)
• 2. Lifting 2-D prints• Electrostatic—used for dry origin
impression• Fingerprint powder
• 3. Casting 3-D prints• Use dental stone, a gypsum product• Stronger than plasters and provided
quicker and easier recovery
Two – Dimensional Impressions
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1. Once an impression has been photographed, the print may be able to be lifted
2. Electrostatic lifting transfers 3. Fingerprint powder in combination with
mikrosil may be used on impressions where electrostatic lifting does not work
Electrostatic Lifting FilmThis foil backed black mylar produces exceptional detail
in even the most subtle dust impressions
Recovery (cont.)
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Electrostatic Lifting Device
Text and image from: Introduction to Criminalistics: The Foundation of Forensic Science By Barry A. J. Fisher, William J. Tilstone, Catherine Woytowicz
Three – Dimensional Impressions
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1. Dental stone is primary means of casting footwear impressions
2. On wet surfaces, a spray wax may have to be used first to seal impression
3. Mix dental stone with water in a ziplock bag for 3 minutes
4. Stone hardens in 20 minutes5. In 24-48 hours it will have fully hardened
Pre-Measured Dental Stone
Recovery (cont.)
Enhancement Methods
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Poor impressions may have to be enhanced by one of the following means:
NOTE: Enhancement similar to fingerprints
Forensic Photography
Oblique, ultraviolet,
infrared lighting
Physical Methods Latent powder, lifting impressions
Chemical Methods
Reagents such as leuco crystal
violet, amido 10 black, or luminol Digital Methods Software such
as Adobe Photoshop can
be used to enhance
impressions
Recovered print Analysis:
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Footwear from Suspected Persons: All footwear a suspect owns should be
seized for comparison
Shoes are needed to make test impressions
• Need to have known shoes and exemplars to compare against
Known Shoes and Preparation of Exemplars
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Known Test Impressions of Footwear- Examiner will make impressions of known footwear and compare them with suspected footwear impression to insure matching samples are highly detailed, and have individual characteristics of shoes
Elimination Footwear – Footwear worn by police officers, medical personnel should be accounted for when considering impressions left at scene
The Examination Process and Conclusions
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Areas of footwear which are examined by analyst include:Design of
shoe
Physical Size and Shape
Wear marks
Individual Identifying
Characteristics- cuts,
tar, gum etc
