1. Forensic Science: Fundamentals & Investigations, Chapter 16 1 Chapter 16 Tool Marks By the end of this chapter you will be able to: o Describe the three major types of tool mark impressions o Summarize the steps of a tool mark examination and analysis o Explain how technology is helping in criminal investigations o Match tool marks with the instrument that produced them All Rights Reserved South-Western / Cengage Learning © 2012, 2009

2. Forensic Science: Fundamentals & Investigations, Chapter 16 2 Introduction o Tool mark—any impression, abrasion, or cut made when contact occurs between a tool and an object An example of physical evidence Even mass-produced tools have minor differences The impressions can link the tool to a crime scene and potentially to the owner

3. Forensic Science: Fundamentals & Investigations, Chapter 16 3 Tools and Crime Scenes o Tools: increase our ability to handle manual tasks, but can also be used in crimes o How can a tool used in a crime lead investigators to the criminal? o Why is ownership of a tool used in a crime circumstantial evidence?

4. Forensic Science: Fundamentals & Investigations, Chapter 16 4 Tool Mark Impressions Indentation Marks o Result when a tool is pressed against a softer surface o Tools usually leave distinctive marks o The hardness of a tool influences the resulting marks left in the softer object o May indicate the size of the tool used in a crime

5. Forensic Science: Fundamentals & Investigations, Chapter 16 5 Tool Mark Impressions Abrasion Marks o An object’s surface can be ground or worn away by a tool o The harder object causes abrasions on the softer surface o Indentation and abrasion marks sometimes occur at the same time

6. Forensic Science: Fundamentals & Investigations, Chapter 16 6 Tool Mark Impressions Cutting Marks o Edged instruments can penetrate a softer object and separate it into parts o Cut marks are produced along the edge as a surface is cut

7. Forensic Science: Fundamentals & Investigations, Chapter 16 7 Tool Mark Impressions Examples of Cut Marks on Bones

8. Forensic Science: Fundamentals & Investigations, Chapter 16 8 Tool Mark Examination o Some experts specialize in tool mark investigations o Evidence can include: tool marks at the scene the tool if left behind

9. Forensic Science: Fundamentals & Investigations, Chapter 16 9 Documenting the Evidence o Collect tool mark evidence when possible o Photograph the evidence with a measuring device to show scale o Measure the size of the impression

10. Forensic Science: Fundamentals & Investigations, Chapter 16 10 Documenting the Evidence o Castings preserve tool mark impressions silicone or rubber-based casting materials o Cast impressions retain the unique indentation marks made by a specific tool

11. Forensic Science: Fundamentals & Investigations, Chapter 16 11 Documenting the Evidence o Dust for fingerprints before applying casting material Use magnetic dusting powder and silicone material o The size of the impression should be measured and recorded.

12. Forensic Science: Fundamentals & Investigations, Chapter 16 12 Collecting and Preserving a Sample o Correctly label evidence o Wrap small objects with clean paper and place them in small containers or plastic bags o Pack large objects in cartons or boxes o Record—who, where, when, and why o Maintain the chain of custody

13. Forensic Science: Fundamentals & Investigations, Chapter 16 13 Analyzing Tool Mark Evidence o Laboratory tool mark analysis identifies: major characteristics defining the type of tool used in a crime unique characteristics that might distinguish between the same kinds of tools o Forensic comparison microscopes examine tool mark characteristics that match a suspect tool

14. Forensic Science: Fundamentals & Investigations, Chapter 16 14 New Technology in Tool Mark Identification Courts now require more than visual pattern comparisons o Tool mark databases (with images acquired by forensic comparison microscopes) o Algorithms to statistically analyze tool mark patterns o Scanning tools measure the depth or height of tool marks

15. Forensic Science: Fundamentals & Investigations, Chapter 16 15 Tool Mark Evidence in the Courtroom o The tool mark witness prepares a written report to present to a jury. o When available, provide: Original evidence Castings Magnified images of tool mark comparisons o Such evidence may link a series of crimes

16. Forensic Science: Fundamentals & Investigations, Chapter 16 16................. Summary................. Summary o Tools have major and minor surface differences o Tool marks are indentations, abrasions, or cut marks o Impressions made by tools could link them to a crime scene and ultimately to the owner o Tool mark evidence should be photographed, documented, and collected or cast