20 Forensic Science Powerpoint Chapter 20 Forensic Tire Impress

18,850 views

Published on

Published in: Technology, Education
1 Comment
17 Likes
Statistics
Notes
  • this presentation is very useful with much practical knowledge
       Reply 
    Are you sure you want to  Yes  No
    Your message goes here
No Downloads
Views
Total views
18,850
On SlideShare
0
From Embeds
0
Number of Embeds
492
Actions
Shares
0
Downloads
636
Comments
1
Likes
17
Embeds 0
No embeds

No notes for slide

20 Forensic Science Powerpoint Chapter 20 Forensic Tire Impress

  1. 1. Forensic Science An Introduction to Scientific and Investigative Techniques Stuart H. James and Jon J. Nordby Chapter 20 CRC Press: Forensic Science, James and Nordby, 3rd Edition
  2. 2. Chapter 20 <ul><li>Forensic Tire Tread and Tire Track Evidence </li></ul><ul><li>Chapter Author: William J. Bodziak </li></ul><ul><li>Presentation created by Greg Galardi, Peru, Nebraska </li></ul><ul><li>Edited by Stuart H. James, Fort Lauderdale, Florida and </li></ul><ul><li>Dan Mabel, Richmond, Virginia </li></ul>Chapter 20 CRC Press: Forensic Science, James and Nordby, 3rd Edition
  3. 3. Forensic Tire Tread and Tire Track Evidence <ul><li>Tire impressions reflect the tread design and dimensional features of individual tires on a vehicle </li></ul><ul><li>Tire Tracks are relational dimensions between two or more tires: tracks can be used to determine the wheelbase of the vehicle </li></ul>Chapter 20 CRC Press: Forensic Science, James and Nordby, 3rd Edition
  4. 6. Original Equipment Tires, Replacement Tires and Tire Construction <ul><li>Original Equipment Tires - tires sold on new equipment </li></ul><ul><li>Replacement tires – those used to replace worn or damaged tires </li></ul><ul><li>Most tires today are of radial ply construction </li></ul><ul><li>Tires are composed of liner, sidewall rubber, beads, belts and tread rubber </li></ul>Chapter 20 CRC Press: Forensic Science, James and Nordby, 3rd Edition
  5. 7. Tread Nomenclature and Sidewall Information <ul><li>Tire treads are composed of design elements separated by grooves </li></ul><ul><li>Grooves which run across a tire are called slots or transverse grooves </li></ul><ul><li>Tread wear indicators – raised areas which indicate tread wear </li></ul>Chapter 20 CRC Press: Forensic Science, James and Nordby, 3rd Edition
  6. 9. Tread Nomenclature and Sidewall Information <ul><li>Department of Transportation number, known as DOT number – consists of: </li></ul><ul><li>DOT AC L9 ABCD 4901 </li></ul><ul><li>DOT impression </li></ul><ul><li>Plant code and manufacturer </li></ul><ul><li>Date of manufacture </li></ul><ul><li>Tires made after January 1, 2000 have four numbers in last group, while prior to that there are three numbers </li></ul>Chapter 20 CRC Press: Forensic Science, James and Nordby, 3rd Edition
  7. 11. Tread Nomenclature and Sidewall Information <ul><li>Retread tires – have slightly different numbers </li></ul><ul><li>DOTR YPY 1201 </li></ul><ul><li>DOTR – Department of Transportation retread </li></ul><ul><li>YPY – Manufacturer retread </li></ul><ul><li>1201 – date and year of manufacture </li></ul>Chapter 20 CRC Press: Forensic Science, James and Nordby, 3rd Edition
  8. 13. Tread Nomenclature and Sidewall Information <ul><li>Common tire size designation includes: </li></ul><ul><li>P 195 / 65 R 15 </li></ul><ul><li>P – passenger tire </li></ul><ul><li>195 – approximate width in millimeters </li></ul><ul><li>65- aspect ratio </li></ul><ul><li>R – radial tire </li></ul><ul><li>15 – rim diameter in inches </li></ul>Chapter 20 CRC Press: Forensic Science, James and Nordby, 3rd Edition
  9. 14. Noise Treatment <ul><li>Stress Cycle - Under load of a vehicle, rotating tire goes through stress </li></ul><ul><li>Contact Patch – portion of tire touching ground </li></ul><ul><li>Noise treatment – tire industry created tire designs that vary the size (pitch) design elements of tire. This reduces or controls noise emitted by tire </li></ul>Chapter 20 CRC Press: Forensic Science, James and Nordby, 3rd Edition
  10. 15. Noise Treatment <ul><li>Mixture of three design elements, small (S), medium (M) and large (L) allow manufacturers to change size of tires and minimize noise </li></ul><ul><li>Noise treatment is different on opposite sides of tire </li></ul>Chapter 20 CRC Press: Forensic Science, James and Nordby, 3rd Edition
  11. 18. Tread Wear Indicators <ul><li>Tread Wear Indicator, or known as a wear bar, is a raised rubber bar 1/16 of an inch above base of grooves of tire </li></ul><ul><li>DOT requires all tires contain a minimum of six tread wear indicators </li></ul><ul><li>As tread wears down on tire, these become noticeable and indicate tire needs replacement – these indicators can be retained in 3-D impressions </li></ul>Chapter 20 CRC Press: Forensic Science, James and Nordby, 3rd Edition
  12. 19. Retread Tires <ul><li>Retread tires are primarily used for commercial or fleet vehicles in United States </li></ul><ul><li>Two types of retread processes: </li></ul><ul><ul><li>Mold Cured Process </li></ul></ul><ul><ul><li>Pre-Cured Process </li></ul></ul><ul><li>Some retread tires have valuable individual characteristics which provide information to the examiner </li></ul>Chapter 20 CRC Press: Forensic Science, James and Nordby, 3rd Edition
  13. 20. Tire Track Evidence <ul><li>Tire track evidence consists of : </li></ul><ul><ul><li>Tire track width </li></ul></ul><ul><ul><li>Wheelbase dimensions </li></ul></ul><ul><ul><li>Turning diameter </li></ul></ul><ul><ul><li>Relative positions of turning tracks </li></ul></ul>Chapter 20 CRC Press: Forensic Science, James and Nordby, 3rd Edition
  14. 21. Tire Track Evidence <ul><li>Track Width (Stance) – measurement made from one center of one wheel to opposite center of wheel </li></ul><ul><li>Front wheels turning produce unreliable measurements </li></ul><ul><li>Rear wheels accurately record turns </li></ul>Chapter 20 CRC Press: Forensic Science, James and Nordby, 3rd Edition
  15. 23. Tire Track Evidence <ul><li>Wheelbase – measurement of center of hubs of front wheels to center of hubs of rear wheel </li></ul><ul><li>Normally these measurements are not present at crime scenes </li></ul>Chapter 20 CRC Press: Forensic Science, James and Nordby, 3rd Edition
  16. 25. Tire Track Evidence <ul><li>Turning Diameter – Diameter of circle a vehicle makes when its steering wheel is fully turned – pertains to front wheels only </li></ul><ul><li>Turning diameter is measured by (B squared/A) + A, where: </li></ul><ul><li>B = distance between two points ( x and x’) on turn circle </li></ul><ul><li>A = distance between outer margin and a mid point between x and x’ </li></ul>Chapter 20 CRC Press: Forensic Science, James and Nordby, 3rd Edition
  17. 27. Tire Positions in a Turn <ul><li>When vehicle moves in straight path, only rear tire tracks are available </li></ul><ul><li>When a vehicle turns, rear and front tires rack separately </li></ul><ul><li>Important to understand and document at crime scenes </li></ul>Chapter 20 CRC Press: Forensic Science, James and Nordby, 3rd Edition
  18. 29. Recovery of Evidence <ul><li>Tire impressions must be: </li></ul><ul><ul><li>Photographed from all angles with and without measurement tool (ruler) </li></ul></ul><ul><ul><li>Cast – a 3 foot impression requires 15-25 pounds of dental stone </li></ul></ul><ul><ul><li>Measured – width, length and depth </li></ul></ul><ul><ul><li>Direction of travel noted </li></ul></ul><ul><ul><li>Impressions made if possible, and </li></ul></ul><ul><ul><li>Pictures of the source (tire) must be included for comparison </li></ul></ul>Chapter 20 CRC Press: Forensic Science, James and Nordby, 3rd Edition
  19. 30. Known Tires and Exemplars <ul><li>Tire tread examinations compare the tire impressions recovered from scene with tires taken from a known vehicle </li></ul><ul><li>Two categories of tires: </li></ul><ul><ul><li>Suspect - Vehicle of suspect </li></ul></ul><ul><ul><li>Elimination - Vehicles of police, ambulance, etc </li></ul></ul><ul><li>All tires should be seized from suspect vehicle for comparison </li></ul>Chapter 20 CRC Press: Forensic Science, James and Nordby, 3rd Edition
  20. 31. Tire Impression, the Examination Process, and Conclusions <ul><li>Tire impressions are resulting transfer of tread detail of a tire against a substrate </li></ul><ul><li>Impressions can be three or two dimensional </li></ul><ul><li>Forensic examination begins with visual comparison and elimination of tires which do not match impression </li></ul>Chapter 20 CRC Press: Forensic Science, James and Nordby, 3rd Edition
  21. 32. Tire Impression, the Examination Process, and Conclusions <ul><li>Forensic examination continues with full circumference test impressions </li></ul><ul><li>Impressions are superimposed on known impression over cast or original tire </li></ul><ul><li>Other factors to be evaluated are tread design, tread dimension, noise treatment, wear features and random individual characteristics </li></ul>Chapter 20 CRC Press: Forensic Science, James and Nordby, 3rd Edition

×