School Essay: Glass & Soil Crime Scene

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.