Soil-analysis,toolmarks, casting, and molding1.pptx

Forensic science

1. CHAPTER 11 SOIL ANALYSIS, TOOLMARKS, CASTING, AND MOLDING

2. Learning Objectives At the end of this chapter, the student will be able to: Describe the process of soil sample collection; Enumerate the steps in soil sample analysis; Define "tool marks" and describe their characteristics: Describe the process of preserving and packaging tools; Define "casting and molding and describe these processes; Enumerate the types of tire impression/tire track examinations And Identify the steps in the examination of shoe prints and tire impressions.

3. What is soil? Soil consists of plants, minerals, animal matter, and tiny particulates of synthetic products such as cement, paint, glass, asphalt, and so on. Soil contents are not uniform and they differ from one place 10 another. Soil can play an important role in criminal investigation. For example, soil on a suspect's shoe or splattered inside a car fender can provide forensic scientists with sufficient information about the suspects and crime victims. Specifically, soil recovered from clothes, shoes, and automobiles can be analyzed in order to determine if the suspect was or was not in the particular location. sample analysis executed by carefully or impairing shape, mineralogical carefully comparing the particle size and shall sample obtained from a suspect to those from a known location.

4. Collection of Soil Samples Soil sample collection depends on the circumstances of the crime, that is, indoor scenes can differ from outdoor scenes in terms of the type of evidence recovered and the way in which these samples are collected.

5. Indoor Scenes Footprints in soil or in dust samples made by footwear should be photographed to scale prior to recovery. The particle samples are often collected using a vacuum method. Here, the samples are vacuumed with a portable vacuum cleaner equipped with a special attachment, which has a metal screen with a filter paper. The area is vacuumed and the filter is removed and labeled with the name of the technician who operated the vacuum as well as the date, location, and time of collection. Reference samples from the surrounding area (e.g., points of entry and exit and alibi locations) are normally taken.

6. Outdoor Scene Sampling methods are adjusted when the crime scene in outdoors se it involves the recovery of remains, soil samples are taken at ular intervals up to 100 yards from the gravesite or point of recovery. search may also be set up and samples can be taken from each art of the grid and then labeled. Most modern tests just require ait a tablespoon of soil sample. Usually only the surface soil is sampled. However, in the case of a suned body, soil samples are taken at regular intervals as the remains exposed. Once the remains are removed from the gravesite, the tom of the grave should also be sampled. At this point, a new shovel, spoon or other scoop must be used for each grid and sample to avoid cross contamination that can render the samples useless. Several guidelines should be followed. These include the items listed below. Samples should be placed in plastic vials for transport. They should be allowed to air dry prior to transport. If insect evidence is present, vials should be labeled in pencil (not a pen). This is because the specimens are preserved in alcohol, which can leak onto the label and "erase" the ink from pens. Without the label specifying the time and place of collection, the collected sample is forensically worthless.

7. Soil sample from vehicle Vehicles involved in accidents could leave lumps of soil from under the wheel wells and fenders. These should be collected and wrapped in protective material to minimize bumping during transport. At the lab, soil analyst can read these layers and know where this vehicle has Seen. The analyst may also be able to match the layers in a lump of tal to a specific vehicle.

8. Soil Samples from clothing and footwear These should be collected intact and no attempt should be made to remove soil from clothing, footwear or tires. If such items can be moved intact, they should be placed in a paper bag or in a druggist's bold and then placed in a paper bag. The paper bag must be protected so to that evidence is maintained. However, wet sample should be placed than appropriate container because wet samples placed in could quickly rot and become useless.

9. Laboratory Tests for Soil Sample There are several laboratory tests that can be done to examine a soil Sample. 1. Mineral content Determining the ratio of mineral and organic content 2. Electron microscopic examination 3. Density gradient tube method 4 Using heat to test the point at which the sample undergoes an exothermic reaction or an endothermic reaction Exothermic reaction- the sample essentially burns and releases Heat endothermic reaction – the sample absorbs the heat 5. Nuclear resonance and mass spectrometry

10. Steps in Analyzing Soil Samples There are a few steps involved in analyzing soil samples. Visually and microscopically inspecting the soil to make determinations related to consistency, acidity, mineral content and color. Looking for foreign objects, such as plant materials ( eg . like leaves) or animal materials (e.g., hair, nails, teeth). For instance, finding evidence of beachfront sandy soil on the carpets of a suspect's car can contradict his statement that he had never been to the beach on the day the crime in question was committed. On a similar note, finding horse manure in a soil sample could suggest that the soil came from a horse farm and not from the suspect's backyard.

11. Toolmarks When tools such as pliers, screwdrivers, hammers and wire utters are manufactured. the manufacturing process leaves certain perfections embedded on the tools' surfaces. These patterns are unique for each tool. This means that when criminals use a specific tool at a crime scene, the toolmarks left behind can be analyzed by forensic scientists.

12. What are toolmarks? Toolmarks are impressions or marks produced by a tool or instrument on a receptive surface. When the tool makes contact with the surface with sufficient impact to create an indentation, the pattern of the tool is permanently reproduced onto that surface

13. Characteristics of Toolmarks Toolmarks have two kinds of characteristics, namely, class and individual. The class characteristics include its general shape, the type of impression, and its general dimensions. Class characteristics allow the examiner to identify what type of tool created the impression and how the mark was created. Conversely, they do not permit for the identification of the exact tool that created the impression. Thus, if only class characteristics are available on a toolmark , it will not be possible to distinguish which tool made the impression. individual characteristics, also called accidental characteristics, are the striations exhibited by the tool, which are unique to a certain tool. They consist of small, commonly microscopic. ridges, indentations, and irregularities present on the tool itself. For example, the tip of a screwdriver is never perfectly flat, but has small ridges along the edge created by the history of the tool (e.g., use and misuse, cleaning, maintenance, etc.). These characteristics are the ones that allow for a formal identification. If such characteristics are present in the toolmark , then investigators can identify the actual individual tool that created a specific impression.

14. Types of toolmarks There are two main types of toolmarks, namely, slipped and molded impressions. The slipped impression occurs as the tool is dragged across the surface, resulting in toolmarks comprising a series af striations running parallel to each other, following the direction of the drag. For example, such impressions are created by cutting a given material with a knife, by slipping a key across the door of a vehicle, or by cutting an electrical wire using a pair of pliers. the molded impressions result from the contact of a tool onto a surface with no lateral motion (no drag nor slip). The resulting toolmarks are a 3D mold of the part of the tool that touched the surface. Examples of such impressions are the serial number lamped onto a fire-arm's barrel or the leverage of a door from its frame with a pry bar. Some toolmarks are made of a combination of molded and slipped impressions.

15. places and Surfaces Where Toolmarks Might be Observed in Criminal Investigations human bone or cartilage door and window frames sections of sheet metal padlocks, doorknobs wire, chains bolts and locks safety-deposit boxes and safes

16. Toolmark examination is a term that includes a variety of impressions not necessarily directly related to tools but are created via the same fashion. Thus, they are examined with the same techniques. One example is the impression left by firearm's barrel onto a bullet or by the firearm onto the cartridge. These are a specialized category of toolmarks. Other examples include the impressions left by human teeth or even the impressions left by shoes or tires. Often, the toolmark examiner examines and renders expert opinions on such impression's identifications.

17. Preservation and packaging of tools Several guidelines should be followed in preserving and Packaging tools. All areas on recovered tools, which contain building materials, transferred paint, or other contaminants, among others, should be wrapped in paper and packaged properly to prevent the prying blades or cutting edges from contacting any other surface or object. Test marks should never be made prior to laboratory examination. This can alter the tool and make the examination worthless. Moreover, traces of transferred paint or other stains on the tool may be lost or additional material may be transferred to the tool, thus harming its integrity as a piece of evidence. The whole object must be submitted to the laboratory. If this is not possible, the investigator carefully photographs and sketches the area containing the mark. The photograph can assist in determining how the mark was made. Casts of tool marks are made by a person who has had considerable experience in this work. Poor casts are useless for comparison purposes, and some marks can be damaged if improper methods are used. The object containing tool marks should be packed properly so that no alteration or damage will occur during shipment. Small objects should be wrapped with clean paper and placed in envelopes or boxes, while important areas on larger objects can be protected with paper. Meanwhile, large objects can be packed in cartons or crates.

18. Casting and molding refers to the method of extracting an impression using a cast-like plaster of paris inside a mold to recover the pattern for laboratory analysis. When an item like a shoe or a tire comes into contact with a soft surface, it leaves a pattern indicating an impression. The collection and analysis of impression evidence found at the scene of a crime can be crucial in an investigation.

19. Procedure of Casting The steps below outline the proper casting procedure. Take a photograph and measure the impression. Remove loose objects; debris embedded in the surface of impression should be retained. Preserve the impression by spraying it with a fixative agent (hairspray) to make the surface repel the liquid to be poured into. Place a retaining wall on the impression. Mix the plaster of Paris with water with a 7:1 ratio. Pour the plaster of Paris mixture into the impression. Place the reinforcement material. Pour the remaining mixture until it is 1-inch thick. Allow the cast to harden for about 20 to 30 minutes.

20. Shoe Prints Shoes create impressions called shoeprints, which can be extremely informative to forensic investigators. The sole of a shoe picks up various kinds of debris as a person walks that are then transferred to other surfaces, creating an impression that could help reveal the pattern on the sole. Investigators look at the soil, particularly those around the potential entry and exit points of a crime scene, as well as carpet, linoleum, paper, and dust to detect shoeprints. More importantly, if a shoeprint is found in a pool of blood, it can serve as an incriminating evidence. There are three kinds of shoeprints: patent, plastic, and latent. Patent shoeprints are clearly visible and come from tracking through a substance such as paint or dirt, leaving some of these behind each time a step is taken. A plastic shoeprint occurs when a shoe sinks into a soft substance such as mud. Latent shoeprints are not visible to the naked eye and often occur on a hard surface such as glass or concrete The techniques used for collecting shoeprints include electrostatic lifting, dusting with special powders, and making plaster casts. A photographic record is also taken as a backup

21. Tire Tracks Tire tracks refer to the impressions left by tires on the surface onto which a vehicle drove. Not all tires and surfaces will leave tire tracks. the surface is soft, the tire leaves an imprint under the weight of the vehicle. Meanwhile, if the surface is hard, the tire might still leave a trace, if dirt or dust was present. Similar to shoeprints or fingerprints, tire tracks are important in forensic investigations, because they allow the identification of the vehicle that left them. For example, tire tracks are often found in road accident scenes or in the access and escape mutes of other crime scenes.

22. Conclusion In conclusion, the analysis of soil, toolmarks, casting, and molding plays a crucial role in forensic investigations. Soil analysis can provide valuable information about the origin and composition of soil found at a crime scene, helping investigators determine possible locations or associations. Toolmark analysis allows forensic scientists to examine the unique patterns left behind by tools used in the commission of a crime, aiding in the identification of the specific tool used and potentially linking suspects to the crime. Casting and molding techniques are employed to create replicas of toolmarks or other impressions found at a crime scene, allowing for further analysis and comparison. These forensic techniques provide important evidence and insights in criminal investigations. Soil analysis can help establish connections between suspects, victims, and crime scenes. Toolmark analysis can help identify the tools used in a crime and link them to potential perpetrators. Casting and molding techniques allow for the preservation and analysis of physical evidence, which can be crucial in solving cases.

23. Tire Impression Tires are made of semi-hard rubber characterized by class and Individual characteristics. Individual characteristics include accidental cuts or holes and regular wear and tear, while class characteristics include size and general patterns. Such characteristics may be reproduced in the tracks left by the tire, depending on the surface and the circumstances under which the tracks have been created. When examining a crime scene containing tire tracks, forensic science can play a great role in establishing the identity of a vehicle present at the scene and matching that with a vehicle of a suspect.

24. Types of Examination There are two kinds of tire track examinations. Comparative examination this is conducted to determine whether a known shoe or tire made the impression; and Investigative examination these are conducted on impressions to provide information regarding manufacture or design descriptions that can provide investigative leads

25. The characteristics of impression evidence that could facilitate a comparative examination consist of three elements, namely; Wear patterns -As the shoe or tire is worn or used on a vehicle, the pattern area will wear down with the erosion of the trend or sole material. This wear pattern follows a "normal progression." However, other factors, such as the walking pattern or gait of an individual wearing the shoes, or the front end misalignment of the tires on a vehicle could have an effect on the overall wear pattern. The wear pattern alone will not provide the basis for positive identification. Design characteristics-These cover the basic pattern of the shoe sole or tire tread design. These patterns are patented although illegal copies can be reproduced specific to a manufacturer, Shoes or tires have this basic pattern design. Accidental characteristics -During the normal use of the shoe or tire, some damage (e.g., cuts and nicks are left on the tread surface. These characteristics are known as “accidental” and occur randomly on all tire and shoe designs. In forensic examination, the match of accidental characteristics may allow for the positive identification of a particular shoe or tire having made a particular impression.