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Physical Evidence Chapter 3

Physical Evidence Chapter 3. Physical Evidence. Blood, Semen, Saliva Documents Drugs Explosives Fibers Fingerprints Firearms and Ammunition Glass Hair Impressions. Physical Evidence. Organs and Physiological Fluids Paint Serial Numbers Tool Marks Other. Physical Evidence.

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Physical Evidence Chapter 3

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  1. Physical EvidenceChapter 3 CHE 113

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

  3. Physical Evidence • Organs and Physiological Fluids • Paint • Serial Numbers • Tool Marks • Other 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)? 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. 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. Common Origin? 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. 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. Blood Types World: Type A - 42% Type B - 8% Type O - 47% Type AB - 3% US: Type A - 39% Type B - 13% Type O - 43% Type AB - 5% CHE 113 “Bodies of Evidence” Brian Innes

  9. Class Characteristics Where is Waldo? • Properties of evidence that can only be associated with a group and never with a single source. • Can be used to exculpate a suspect. • Examples: single-layer paint chip, blood, nylon fiber from a sweater 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. Example: from “My Cousin Vinny” (20th Century Fox) 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. CHE 113

  12. Use of Class EvidenceEffect of “Scientific Expert” on JuryRight to have “counter experts” 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. 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 Blood Types World: Type A - 42% Type B - 8% Type O - 47% Type AB - 3% US: Type A - 39% Type B - 13% Type O - 43% Type AB - 5% 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 CHE 113

  16. Disdvantages of Class Physical Evidence Next Film Clip Shows Many Impt. Ideas about evidence: Disadvantages of Class Evidence (especially for mass produced popular items). Expert Qualifications How Class Evidence may be turned into individual evidence. Weight accorded by juries to scientific evidence Voir Dire - “speaking the truth” - challenging potential jurors and expert witnesses’ qualifications CHE 113

  17. How Class Evidence may be turned into individual evidence.My Cousin Vinny conclusion 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. Body of a woman was found with a knife wound in her neck. A broken knife tip was found in the wound. The knife blade tip was compared with the knife found in the husbands pocket. Matches both in brake line and scratches. CHE 113 Saferstein Fig. 3.1

  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 Firearms ID CHE 113

  20. Physical Evidence CHE 113

  21. Physical Evidence Lindberg Kidnapping Case 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. CHE 113

  23. Lindberg Kidnapping • Ladder Used in Abduction CHE 113

  24. 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. CHE 113

  25. Crime-Scene Reconstruction Step 1 - State problem - type of crime and the legal elements. Step 2 - Collect data - - records checks and police checks, interview victim, witnesses, and suspects, try to get additional witnesses and comparison samples from suspects Step 3 - Form a hypothesis - look at all evidence - determine motive and possible suspects Step 4 - Test hypotheses - evaluate how truthful and reliable the stories are, weigh their stories against the physical evidence Step 5 - Follow up the most promising hypotheses (theories) Step 6 -- Draw conclusions - supported by court-admissible evidence leading to the arrest, prosecution, and conviction of the offender.   CHE 113

  26. Homicide:Rape:Robbery:Burglary: 1- focus on deceased 1- focus on victim 1 - modus operandi 1 - focus on scene 2 -crime scene 2 - medical reports 2 - crime scene 2 - records check 3 - crime lab 3 - crime scene 3 - police records 3 - property check 4 - usual suspects Source: adapted from Gilbert, J. (1980) Criminal Investigation. Columbus: Merrill. Patterns -- series of similarities that indicate the same person or the same modus operandi is involved in different crimes. Leads -- clues or breaks in the case that move an investigation forward. Tips -- provided by informants. Tips by definition involve specifics. Theories -- beliefs that point in one direction, at the exclusion of other possible directions. Clues -- pieces of evidence that are consistent with the corpus delecti or elements of the crime. CHE 113

  27. Physical Evidence CHE 113

  28. Crime-Scene Reconstruction Saferstein “Criminalistics” CHE 113

  29. Kennedy Assassination PETER JENNINGS REPORTING: THE KENNEDY ASSASSINATION: BEYOND CONSPIRACY ABC News Special (Nov. 2003) CHE 113

  30. End Chapter 3 CHE 113

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