fc103-chap-12- crime scene examination.pptx

forensic chemistry crime scene examination discussion.

1. CHAPTER XII TOOL MARKS

2. TOOL A tool is an instrument or object capable of making a mark on another object. A tool mark is defined as any impression, cut, scratch, gouge, or abrasion, or any other marking left on an object by another harder object or instrument. A tool mark may be classified as a negative impression , as an abrasion or friction-type mark or as a combination of the two. Negative impression is made when a tool is pressed against or into a receiving surface. This type of mark is usually made when a crowbar is used to pry open a door or a window.

3. Abrasion or friction mark is made when a tool cuts into or slides across a surface. This type of mark may made by a pair of pliers, a bolt cutter, knife, ax, s aw, drill, plane, or a die used in the manufacture of wire. Combination of mark is made, for example, when a crowbar is forcefully inserted into the space between door and the door facing and pressure is applied to the handle of the tool to force the door open.

4. Application of Tool mark knife marks on bone fractured knife blades homemade explosive devises

5. Application of Tool mark crimp marks on detonation cut marks on wire pry marks on a window or door

6. what information can a tool mark provide?? 1. The type of tool 2. Shape of the cutting edge of a blade 3. Blade width 4. Color of the tool (based on the paint transfer from the tool) 5. Class characteristics of the tool 6. Unique identifying marks

7. Use of Tool Mark Evidence Tool mark may be used to: a. link a person who used the tool in the commission of the crime, or some oth er acts material to the commission of crime b. establish whether a given tool or weapon found at the crime scene has made a mark that is material to the crime; c. establish a connection between similar evidence discovered in a series of crimes d. determine whether a door or window was forced open from the inside or outside. e. compare a tool mark from a crime scene with a tool mark found on the property, equipment or vehicle of a suspect; and f. facilitate and narrow the search for a given tool

8. Why are Tool Marks Important in Crime Scene Investigation??? Tool marks are important in crime scene investigation because you c an tell what kind of tool was used, and by that you can see if the suspect’s tools match the tool mark. Tool marks are usually discovered on doors, windows and other openings that may have been used by a criminal in their forcible entry or exit. Particular att ention must be focused on broken, forced or cut lock and the immediate area surrounding these fastenings. Entire crime scene and its vicinity must be searched for tool that may have been used. Whenever possible, submit the whole object containing tool marks to the laboratory instead of just the area containing the mark. If this is not possible, carefully photograph and sketch the area containing the mark. Casts of tool marks can be made by a person who has had considerable experience in this work. Poor casts are useless for comparison purposes and some marks will be damaged if improper methods are used.

9. Preservation and Packaging of Tools Package the object containing tool marks 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 or larger objects can be protected with paper. Whole, large objects can be packed in cartons or crates, if not delivered in person . Test marks are made with suspected tools on material similar to t hose on which the tool marks are present and c ompared with suspected tool marks by using comparison microscope.

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