Written
Assignment #3: Glass & Soil Crime Scene
Leslie
K. Penny
Chancellor
University
Abstract
The facts of the case
are simple, a small business is robbed via entry through the front plate glass
window. A suspect is found a short
distance from the crime scene with mud and glass on his shoes. Evidence is immediately collected and tagged
from the suspect as well as from the crime scene which consists of glass and
soil. All the steps in the investigation
are done properly and the forms filled out accordingly including the chain of
custody. The evidence was immediately
taken to the forensic scientists where specific tests were given on each sample
to match the soil and glass from the suspects shoes with the soil and glass at
the crime scene. The answers provided by
the forensic scientists indeed placed the suspect at the crime scene.
Written
Assignment #3: Glass & Soil Crime Scene
The following case is a robbery scenario. The robbery took place at a small store near
a vacant lot at night. The source of
entry is through the stores front plate glass window which was broken into, not
opened. A suspect was located by the
responding officers a quarter of a mile from the crime scene and is placed
under arrest. Upon examination, the
suspects shoes are found to have glass particles embedded in mud on the
bottoms. As per this case, the following
objectives will be met: a full description of the soil and glass evidence
found, where it was found, how it's to be collected and packaged, what tests
are to be done by the forensic scientists in their labs and what information
could be provided by the testing to connect the suspect to the crime
scene.
As the investigator, my first priority is taking the
suspects shoes into evidence. I would
first get pictures of the suspect wearing the shoes then I would take the shoes
off as carefully as possible on top of something to catch any debris that may
fall off. Once the shoes are off the
suspect I would take photo's, tops, sides and bottoms (as many angles as
necessary) and then wrap each shoe in paper and package them in a plastic bag or box. I wouldn't take any of the mud or glass off
the shoes. I would leave that for the
forensic scientists. I would ensure the
evidence bag or box has the proper information to include the contents, the
time, date and where the evidence was collected.
Next thing I would do is take notes of the evidence
collected so far describing the mud, i.e. color, texture, thickness, and a
description of the glass as well, color, thickness and size. Since this is a
scenario I will do just that. The mud is
dark black like fresh top soil. It is
smeared on the sides of the shoe and clumped in the treads. The texture looks flakey and is drying
rapidly becoming brittle falling away from the shoes in areas. The glass is very small slithers and if it
weren't for the nature of the very small but deep tread on the suspects shoes
with the combination of mud the glass more than likely wouldn't have clung so
well. The glass is opaque white and has
no other indentifying marks.
At this point the suspect has been searched for any other
evidence that can further link him to the crime. Fingerprints have been taken as well as a DNA
sample. The suspect is currently being
interrogated. While all that is going on
I'm at the crime scene collecting further evidence from the broken window and
the soil surrounding the property, especially under the broken window.
The ground on the outside of the stores front shattered
window is very wet. I see what looks to
be freshly planted shrubs and flowers.
To the side of the building is a stack of mulch and a coiled up water hose not in use. Underneath the hose are several empty bags of
topsoil. It hasn't rained in several
days so at this time the conclusion is the store owner recently laid topsoil
when he planted new plants and thoroughly watered them earlier that evening at
closing causing the mud. All of this
will be confirmed with the owner upon his arrival on the scene.
There are foot prints under the window in which casts
have been made as well as some larger shards of glass. The majority of the glass is in the inside of
the store below the window and a few feet in from the force of the hit. Five feet into the room is a rock the size of
a medium orange that at this time looks to be the object that was used to break
into the store.
Pictures, sketches and notes are taken of the outside and
inside of the store before evidence is collected. A sample of the mud outside the store as well
as a bit on the window sill are collected and bagged separately in plastic bags
since the mud is still wet, otherwise I
would put the samples in manila envelopes.
I would want to ensure my evidence containers or bags are fresh and have
never been used, are leak proof and sealable, and that I "uphold the
integrity of each item of evidence by using separate containers.", keep
the evidence from direct sunlight and heat and that I handle the evidence as
little as possible (Osterburg & Ward, 2004, p.124-125).
The shards of
glass found on the outside of the store are placed in a cardboard box due to
their size. Every single piece of glass
is picked up for the forensic scientists.
A cardboard box is used for the glass on the inside of the store as well
due to some of the bigger pieces. The
smaller pieces are picked up using forceps and placed in screw-cap glass vials
for smaller pieces or a vacuum specifically for crime scene evidence removal
(Saferstein ,2007, p. 49). Every last piece of glass is collected and
each parcel of evidence is listed with its contents, where found, and
when. I would also ensure that each
container of evidence is properly documented to adhere to the chain of custody
standards for eventual court use.
Now that the evidence is contained properly and an
evidence submission form is completed, it now makes its way to the forensic
scientists either by me personally or someone on my team, or by mail
shipment. Once the forensic scientists
have "custody" so to speak of the evidence they will begin testing
the items. The forensic scientist would
first want to identify the evidence given to them. In this case, I have identified the mud as
more than likely being topsoil and the glass is easily identifiable but testing
gives an absolute definite as to what exactly the substances are.
The majority of this case has to do with comparison. the forensic scientists have in their custody
evidence from the crime scene and evidence from the suspect that upon visual
inspection looks very similar. However,
the evidence needs to be subjected to a comparison analysis which means "a
suspect specimen and a standard/reference specimen" endure "the same
tests and examinations for the ultimate purpose of determining whether they
have a common origin" (Saferstein ,2007,
p. 72).
I believe the glass would be considered to have
individual characteristics sense it could be fit together like a jigsaw puzzle
which narrows down the testing. Forensic
scientist would want to see what type of glass came from the crime scene and
what type of glass came from he suspects shoes by "finding and measuring
the properties that will associate one glass fragment with another while
minimizing or eliminating the possible existence of other sources"
(Saferstein, 2007, p. 110).
In this case, the glass fragments from the suspects shoes
are more than likely too small to be fitted back together so they will now need
to do a chemical comparison of the glass by using a flotation method to compare
the densities of the glass found at the crime scene and on the suspects shoes. Another method to be used is the immersion
method where the "glass particles are immersed in a liquid medium whose
refractive index is objected until it equals that of the glass particles"
(Saferstein, 2007, p.111).
The forensic
scientists would then use heat known as the hot stage (Saferstein, 2007,
p.112). Once these tests have been
completed, they can now compare the density and refraction index values for
their frequency of occurrence and evaluate the probability of the fragments
origin as indeed being that of the store front window. The tests given also depends on the glass
such as tempered and non-tempered, for example.
The distinction between these two can be made simply by slowly heating
and then cooling the glass called annealing (Saferstein, 2007, p.115).
The forensic scientist must also examine the glass to see
in which direction the glass was
forcefully broken. A glass broken
by a projectile such as the rock found at the crime scene will produce a
fracture pattern where cracks will radiate outward and encircle the hole. The radiating lines are called radial
fractures and the circular lines are called concentric fractures (Saferstein,
2007, p. 116). This information can tell
investigators if indeed it was the rock that busted the pane of glass from the outside.
As for the soil sample, a forensic scientist specifically
trained in geology would be conducting these tests. The book states that most soils can be
differentiated and distinguished by their gross appearance (Saferstein, 2007,
p. 120). The forensic scientist can do a
side-by-side visual comparison of the color and texture of the soil sample that
was brought in as evidence. With this
comparison test they must wait until each sample is dry to get an accurate
visual of the soil. Putting the samples
under the microscope will also reveal similarities in the samples that could
provide a match between the two. The
microscope can reveal plant and animal material and artificial debris and
higher amplification will "help characterize minerals and rocks present in
earth materials" (Saferstein, 2007, P. 120). Saferstein also points out that by carefully
examining and comparing the minerals and rocks naturally present in soil, one
take advantage of the large number of variations between soils and thus add to
the evidential value of a positive comparison (p. 120). Another test used in some laboratories is the
density-gradient tube technique used to compare soil samples. This tests consists of a glass tube filled
from bottom to top with liquids of successively lighter densities and is used
to determine the density distribution of soil (Saferstein, 2007, p. 121).
In conclusion, all the steps have now been taken from the
beginning of the investigation to the conclusion of the forensic scientists
testing and evaluation of the evidence. Each
of these tests run can tell the investigator if the glass and soil found on the
suspects shoes does indeed match the glass and soil collected at the crime
scene. The investigation process, from
the collection and properly tagging the evidence to having the proof provided
by the forensic scientist to link the suspect to the scene is all in a day's
work for the teams outside and inside the crime labs. With their hard work the suspect was indeed
linked to the crime scene.
Reference
Saferstein, R. (2007). Criminalistics: An introduction to forensic
science (9th ed.). New Jersey: Pearson
Prentice Hall.
Osterburg, J., & Ward, D. (2004). Criminal Investigation:
A Method for Reconstructing the Past (4th ed.).
Cincinnati: Matthew Bender & Company, Inc.
