Lesson 3 Footwear Evidence
Pre-lesson Reading
References:
1. http://www.bvda.com/en/prdctinf/dlk_mnl.html
2. http://www.youtube.com/watch?v=qlmZZoLGMpM
(YouTube Video: “Leave No Trace-Footprint Evidence”)
3. http://www.konicaminolta.com/sensingusa/application_notes/3D-Scanning/Bour
nemouth-University-3D-Laser-Scanning-Forensic-Footwear-Evidence
(Bournemouth University: 3D Laser Scanning & Forensic Footwear Evidence)
4.
5.
6.
7.
8.
9.
http://www.maine.gov/dps/msp/criminal_investigation/crimelab/footwear.htm
(Latent Prints-Footwear and Tires)
http://www.state.nj.us/njsp/divorg/invest/criminalistics.html
(New Jersey State Police – Investigations Branch “Impression Analysis)
http://www.sheffield.ac.uk/eee/research/iel/research/lsfootwear.html
(The Lancashire-Sheffield (LS) Footwear Dataset)
http://sciencespot.net/Pages/classforsci.html
(Impression Evidence)
http://library.thinkquest.org/04oct/00206/index1.htm
http://www.shodor.org/ssep/stu/activities/forensic.html
10. http://www.fbi.gov/hq/lab/fsc/current/review/2009_07_review02.htm
(Forensic Science Communications, July 2009-Vol. 11-No. 3)
11. http://tna.europarchive.org/20100413151426/http://scienceandresearch.homeoffi
ce.gov.uk/hosdb/publications/fingerprint-publications/58-06-Fingerprint_and_Fo
otw12835.pdf?view=Binary
(Fingerprint and Footwear Forensics Newsletter (October 2006, Publication
No. 58/06))
12. http://tna.europarchive.org/20100413151426/http://scienceandresearch.homeoffi
ce.gov.uk/hosdb/publications/fingerprint-publications/24-08_FFF_Footmark_Spe
cial_10a0e.html?view=Standard&pubID=555996
(Fingerprint and Footwear Forensics Newsletter (May 2008, Publication No.
24/08))
13. http://tna.europarchive.org/20100413151426/http://scienceandresearch.homeoffi
ce.gov.uk/hosdb/publications/fingerprint-publications/59_07_Fingerprint_and_F
ootw16ebf.html?view=Standard&pubID=514284
(Fingerprint and Footwear Forensics Newsletter (November 2007, Publication
No. 59/07))
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14.
Bodziak, W.J. (1999). Footwear Impression Evidence: Detection, Recovery,
and Examination) (2nd ed.).
Florida: CRC Press.
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Lesson 3
Footwear Evidence
Worksheet 3.1 Introduction of footwear evidence
Footwear impressions are often discovered at the scene of the crime. This evidence
can provide investigators with certain information that can assist them in locating a
suspect.
Sample footprint
Discuss with your group members “What are the important features in footprints and
their significance (refer to the given example)?”:
e.g.
important features
significance
Size of footprint
Real size of suspect’s foot  height of
suspect
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2
3
4
5
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Worksheet 3.2 Photographing footprints
Taking photographs for footprints are very common in a crime scene. Since many
footprints are latent, the impressions may be dusted with fingerprint powder to be
photographed or lifted with tape. They may also be collected using an electrostatic
dust lifting process*.
discovery of footprint by oblique light
Demonstration 1
Use of oblique light source to observe and record latent footprint.
camera
DARK BACKGROUND
observer
torch
Footprint
Want to knows more ?
When parallel light rays enter flat and smooth surface (eg. Glass) the rays will reflect at the same direction with each other.
The reflected image is clear and sharp. This is called regular reflection.
Oblique
light
because
canwillcause
large
degree
ofThe
diffuse
When parallel
light is
raysused
enter rough
surface,itthey
reflect at
different
direction.
reflected reflection,
image is blurred.the
Thislight
is
rays
reflect
from
the
footprint
diverge
in
different
directions
and
make
it
more
visible.
called diffuse reflection.
Regular reflection
Diffuse reflection
Analysis of a footwear impression may include comparing a suspect’s shoe to either
photographs or castings made of dental stone (similar to plaster of paris).
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Demonstration 2
Taking photo of a footwear impression
The same footprint placing on the floor is to be shot by camera at TWO different
angles (case 1 and case 2), the photos taken will be projected on the screen.
Case 1
Case 2
a1
a2
b2
b1
Measure the width and length of the footprints and calculate their ratios.
Ratio :
a
b
Case 1
Case 2
=
=
Real shoe
=
Compare the ratio of case 1 and case 2 with the ratio of the real shoe making the
footprint. Comment on the accuracy of the methods in recording trace evidence in the
crime scene.
_____________________________________________________________________
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_____________________________________________________________________
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Worksheet 3.3 Analysis of footwear impression
Apparatus:
1 sample shoe, 1 A4 carbon paper, 1 paper clay, 3 A4 paper
Experiment
(i)
Put on the sample shoe, then step on a carbon paper with an A4 paper underneath
(both pieces of paper are put on the floor). Collect the footprint left on the A4
paper.
(ii) Clean the bottom of the shoe from any dust. Take out the paper clay and make it
ready for use by squeezing and pressing it on the table until it is flat and large
enough to allow you to put the whole shoe on it. Press a part of the shoe on the
paper clay. Collect the 3D impression casted on the paper clay.
Using the results obtained in (i) and (ii) see whether the footprint of the sample
shoe match that of the suspect (the footprint of the suspect will be projected on to
the screen)
The shoe belongs / does not belong to the suspect.
Give your reasons:
_____________________________________________________________________
_____________________________________________________________________
_____________________________________________________________________
_____________________________________________________________________
_____________________________________________________________________
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Examples of 2D and 3D footprints :
2D footprint on hard surface
3D footprint on mud
Worksheet 3.4 Predictions from footwear evidence
The two footprints shown in Fig. 1 and Fig. 2 are basically identical but there are
some small differences between them:
A
B
C D
E
F
G
A
1
1
2
2
3
3
4
4
5
5
6
6
7
7
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Figure 1
B
C D
E
F
G
Figure 2
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Identify and circle the differences in Figure 2 (Hints: there are 10 differences between
the two sets of footprints)
Write down the coordinates (e.g. A1, D13… ) of the locations of the 10 differences.
_____________________________________________________________________
There are always individual characteristics on a footprint. They may be wear
pattern and specific damage which are formed depending on the walking styles,
walking habits and natures of ground surfaces. These characteristics may be very
small but it can help individualise an impression to a specific shoe.
In Figure 1 & 2, the number of grids containing the footprint’s image is
approximately 80, as a result :
We can tabulate the probability of two shoes from 2 different persons having same
characteristic at the same grid as follows:
Number of Characteristics
1
2
3
Probability =
Probability of Occurrence
1 / 80
number of ways of success
total number of possible outcomes
Calculation:
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With the help of a computer, the footprint can be divided to grids as small as 1 mm2,
an adult shoe (of base area about 100 cm2) consists approximately 10 000 grids, we
can tabulate the probability again as follows :
Number of Characteristics
1
2
3
Probability of Occurrence
1 / 10 000
According to the above calculation, justify whether the footwear evidence is reliable
enough to be used in a criminal court.
_____________________________________________________________________
_____________________________________________________________________
_____________________________________________________________________
_____________________________________________________________________
_____________________________________________________________________
_____________________________________________________________________
_____________________________________________________________________
Want to knows more ?
In probability theory, to say that two events are independent means that the
occurrence of one event makes it neither more nor less probable that the other
occurs. For example:


The event of getting a 6 the first time a die is rolled and the event of getting
a 6 the second time are independent.
If two cards are drawn with replacement from a deck of cards, the event of
drawing a red card on the first trial and that of drawing a red card on the
second trial are independent.
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Worksheet 3.5 Tracking footprints
Measurement of human gait at a crime scene :
A thief left a series of footprints in a house after burglary. What data can we
measure from the gait of the thief? Draw and label them in the figure.
What can be predicted from the human gait ?
_____________________________________________________________________
_____________________________________________________________________
_____________________________________________________________________
_____________________________________________________________________
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Lesson 3
Follow–up activities
1. Chemicals used in recovery of footwear marks
In the beginning of this Lesson, you have watched a video about the recovery of
footprints with bloodstain. The chemical used is actually called “acid violet
17” ,which is a dye that can stain the protein in the blood and form a purple mark. The
chemical formula of the dye is:
www.chemblink.com
Footprints stained with other substances can also be recovered or highlighted by
different methods. The following table summarises a few of them:
Contaminant
Surface
Process
Soil (clay)
Ceramic Wall Tile
Fluorescence Examination
Soil (loam)
White Laminate Shelving
Aluminium Powder
Detergent
Laminate Flooring
Magneta Flake Powder
Grass Stain
PVC floor tile
Superglue / BY40
Milk
Glass
Powder Suspension
Diet Coke
Black Polyethylene
Iodine
Blood stain
Wooden floor
Acid violet 17
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2. The footprints formed by walking backward
In Worksheet 3.5, you learn that the set of footprints pattern may vary according
to the human gaits (walking styles). There were criminals that intentionally walked
backward to leave the crime scene. The purpose of doing that was supposed to
confuse the forensic investigator. However, careful investigation on the footprints
would show that they are unnaturally deep toes comparing with the heel. The
following diagram illustrates a footmark formed by walking backward on a beach:
Teacher may allow students to walk backward in the classroom and let them to
feel the stress on their toes and heels with the ground. Similar results can also be
obtained if we try to identify footprints on hard floor by electrostatic lifting. The
lifted footprint should have denser material (dust) near the toe and less dense near the
heel.
Extended reading:
1.
Bodziak, W.J. (1999). Footwear Impression Evidence: Detection, Recovery,
2.
and Examination) (2nd ed.). Florida: CRC Press.
http://www.fbi.gov/hq/lab/fsc/current/review/2009_07_review02.htm
(Forensic Science Communications, July 2009-Vol. 11-No. 3)
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