Physical Evidence Chapter 3

1. CHE 113 CHE 113 1 Physical EvidenceChapter 3

2. CHE 113 CHE 113 2 Physical Evidence Blood, Semen, Saliva Documents Drugs Explosives Fibers Fingerprints Firearms and Ammunition Glass Hair Impressions

3. CHE 113 CHE 113 3 Physical Evidence Organs and Physiological Fluids Paint Serial Numbers Tool Marks Other

4. CHE 113 CHE 113 4 Physical Evidence Identification - Determination of physical or chemical identity of a substance with as near absolute certainty as the analytical method will permit. What is the material? How certain is the answer? What analytical method(s) will give the best answer (multiple methods)? Comparison - Compares standard and suspect samples to determine if they have a common origin. Can the source of the sample be identified? How certain is the correlation? How many �data points� are necessary to be �certain beyond a reasonable doubt� of the answer (probability)?

5. CHE 113 CHE 113 5 Identification - Determination of the physical and chemical identity of a substance with as near absolute certainty as existing analytical techniques will permit. Examples: drug analysis, species determination & explosive residue that contain dynamite. Example: Gas Chromatography / Mass Spectrometry (GC/MS). Accurate identification of a compound.

6. CHE 113 CHE 113 6 Comparisons Analysis of a suspect specimen WRT a standard/reference (exemplar) specimen to determine whether or not they have a common origin.

7. CHE 113 CHE 113 7 Physical Evidence Class (Group) Characteristics - Properties of evidence that can only be associated with a general group and not with a common source. e.g., blood type, paint or dye lot, etc. Individual Characteristics - Properties of evidence that can connect a sample and standard to a common source (with high probability). e.g., fingerprints, unusual wear patterns, tool marks, etc.

8. CHE 113 CHE 113 8 Physical Evidence Class (Group) Characteristics - Properties of evidence that can only be associated with a general group and not with a common source. e.g., blood type, paint or dye lot, etc.

9. CHE 113 CHE 113 9

10. CHE 113 CHE 113 10 Physical Evidence Class (Group) Characteristics - Properties of evidence that can only be associated with a general group and not with a common source. e.g., blood type, paint or dye lot, etc. Individual Characteristics - Properties of evidence that can connect a sample and standard to a common source (with high probability). e.g., fingerprints, unusual wear patterns, tool marks, etc.

11. CHE 113 CHE 113 11 Physical Evidence Class (Group) Characteristics - Properties of evidence that can only be associated with a general group and not with a common source. e.g., blood type, paint or dye lot, etc. Example: from �My Cousin Vinny� (20th Century Fox) 2 people charged with murder during a robbery at a convenience store (�Sack-O-Suds�). Escaped in an older car and skidded tires while leaving. Witnesses confused but say they saw the two defendants. Expert from FBI called to match tire skids with defendants car.

12. CHE 113 CHE 113 12 Class Physical Evidence

13. CHE 113 CHE 113 13 Advantages of Class Physical Evidence Provides corroboration of events based on objective scientific data The chances of encountering 2 indistinguishable items of class evidence that originated from different sources are variable. Multiple types of class evidence may lead to an extremely high chance that they originated from the same source. Physical evidence has great weight in the courtroom. Class evidence may also serve to exonerate a person.

14. CHE 113 CHE 113 14 Advantages of Class Physical Evidence Multiple types of class evidence may lead to an extremely high chance that they originated from the same source. Type AB blood - 3% Rh Negative - 16% Left-handed - 13% Male - 50% Probability for random match = 0.03 x 0.16 x 0.13 x 0.50 = 0.00031 or ca. 3 in 10,000

15. CHE 113 CHE 113 15 Advantages of Class Physical Evidence Multiple types of class evidence may lead to an extremely high chance that they originated from the same source. Type AB blood = 3% And Red Haired = 3% Rh Negative = 16% And Over 6�2� = 5% Left-handed = 13% Male = 50% Probability for random match = 0.03 x 0.16 x 0.13 x 0.50 x 0.03 x 0.05 = 0.00000047 or ca. 5 in 10 million

16. CHE 113 CHE 113 16 Disdvantages of Class Physical Evidence

17. CHE 113 CHE 113 17 Conclusion of �Vinny�

18. CHE 113 CHE 113 18 Physical Evidence Individual Characteristics - Properties of evidence that can connect a sample and standard to a common source (with high probability). e.g., fingerprints, unusual wear patterns, tool marks, etc.

19. CHE 113 CHE 113 19 Individual Characteristics Properties of evidence that can be attributed to a common source with an extremely high degree of certainty Examples: bullets, knives, shattered headlight

20. CHE 113 CHE 113 20 Physical Evidence

21. CHE 113 21 Physical Evidence Lindberg Kidnapping Case

22. CHE 113 CHE 113 22 Lindberg Kidnapping Chas. A. Lindberg - first to fly solo across Atlantic (1927). One of the most famous Americans in the �20�s and �30�s. June 22, 1930, Chas. Lindberg Jr. born: Mar. 1, 1932 he was kidnapped.

23. CHE 113 CHE 113 23 Lindberg Kidnapping Ladder Used in Abduction

24. CHE 113 CHE 113 24 Lindberg Kidnapping Ladder Used in Abduction

25. CHE 113 CHE 113 25 Lindberg Kidnapping Ladder Used in Abduction

26. CHE 113 CHE 113 26 Crime-Scene Reconstruction Collaborative effort of law enforcement personnel, medical examiners and criminalists Was there more than one person involved? How was the crime committed? Reconstruction supports likely sequence of events by the observation and evaluation of physical evidence and statements made by witnesses and those involved with the incident Reconstructions can play a vital role in aiding the jury to arrive at an appropriate verdict.

27. CHE 113 CHE 113 27 Crime-Scene Reconstruction

28. CHE 113 CHE 113 28

29. CHE 113 CHE 113 29 Physical Evidence

30. CHE 113 CHE 113 30 Crime-Scene Reconstruction

31. CHE 113 CHE 113 31 Kennedy Assassination

32. CHE 113 CHE 113 32 End Chapter 3