1 / 19

Chapter 3 Physical Evidence

Chapter 3 Physical Evidence. What is Physical Evidence?. Any and all objects that can establish that a crime has been committed OR can provide a link between a crime and it’s victim or a crime and its perpetrator. Common Types. Blood, semen, saliva Documents Drugs Explosives Fibers

louis-gill
Download Presentation

Chapter 3 Physical Evidence

An Image/Link below is provided (as is) to download presentation Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author. Content is provided to you AS IS for your information and personal use only. Download presentation by click this link. While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server. During download, if you can't get a presentation, the file might be deleted by the publisher.

E N D

Presentation Transcript

  1. Chapter 3 Physical Evidence

  2. What is Physical Evidence? • Any and all objects that can establish that a crime has been committed OR can provide a link between a crime and it’s victim or a crime and its perpetrator.

  3. Common Types • Blood, semen, saliva • Documents • Drugs • Explosives • Fibers • Fingerprints • Firearms and ammunition

  4. Common Types 8. Glass 9. Impressions 10. hair 11. Organs and Physiological fluids 12. Paint 13. Petroleum products 14. Plastic bags 15. Plastic, rubber, polymers

  5. Common Types 16. Powder residues 17. Serial numbers 18. Soil and minerals 19. Tool marks 20. Vehicle lights 21. Wood and vegetative matter

  6. Identification • Process of determining a substance’s physical or chemical identity. • Drug analysis • Species determination: human or not • Explosive residue analysis

  7. Identification • Steps Involved: • Design systematic analysis that will always test for that substance • Testing must eliminate all other possibilities • Some substances require 1-10 tests • FS must be prepared to render a conclusion with respect to the origin of the specimen

  8. Comparison • Attempts to ascertain whether two or more objects have a common origin. • Use properties of suspect and control. • Gives conclusions as probability • Two types of characteristics

  9. Comparison:Two types of characteristics • Class characteristics: • Substances can be associated with a group but not individual source • Blood types: use factors in blood • A lot of these can ID suspects at a crime scene • Individual characteristics: • Substances that are related at almost 100% probability • Fingerprints are 1x1060 that 2 peoples are the same

  10. Do Now 10/14: • Get out Lab due today: hair analysis • Put in team folders

  11. The Product Rule (Probability) • Multiplying together the frequencies of independently occurring events • Rolling 2 dices and getting sixes • 1/6 x1/6= 1/36

  12. The Product Rule (Probability)

  13. O.J.’s bloodstain frequencies

  14. Fiber Evidence and the Wayne Williams Trial • Items from residence and station wagon.

  15. Fiber Evidence and the Wayne Williams Trial • Tracking Carpet fiber between the two victims • Assuming: • Carpet installed in one room • 12x5’ room • Total sales divided between 10 states • SO 82 rooms with this carpet in Georgia • Product rule (probability) =1 : 7,792 • Very low chance

  16. Crime scene reconstruction • The method used to support a likely sequence of events by the observations and evaluation of physical evidence, as well as statements made by witnesses and those involved with the incident.

  17. Crime scene reconstruction

  18. For CSR • Medical examiner • Law Enforcement personnel, • Criminalists

  19. Finis’

More Related