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Do now: What types of things should be in a crime scene sketch?

Do now: What types of things should be in a crime scene sketch?. THE CASE: A steady stream of people enter Butch’s place of business and remove its treasured belongings. The people do not pay for what they take. Butch allows them to take as much as they can carry as long as they keep quiet.

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Do now: What types of things should be in a crime scene sketch?

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  1. Do now: What types of things should be in a crime scene sketch?

  2. THE CASE: A steady stream of people enter Butch’s place of business and remove its treasured belongings. The people do not pay for what they take. Butch allows them to take as much as they can carry as long as they keep quiet. THE MYSTERY: What type of business employs Butch and what are the people taking? CLUES: Businesses like Butch’s exist in every city in the U.S. Butch makes sure his shelves are always stocked with merchandise. Butch does more lending than selling. The city government runs and owns Butch’s place of business. Sometimes Butch makes people pay them when they bring the belongings back. But sometimes thinks of his customers as “worms.”

  3. Physical Evidence Aim: How do we collect and identify physical evidence?

  4. Introduction to Physical EvidenceThe Value of Physical Evidence (reading) Recognize, Collect, & Preserve The roles of Physical Evidence: • Reconstruct the Crime Scene & Sequence of Events • Determine whether or not a crime occurred. • Link an individual with another or with a crime scene • Provide Investigative Leads to Investigators. • Provide facts to a jury which may assist in the determination of the guilt or innocence of an accused. • Provide evidence to link serial homicide or rape case.

  5. Advantages of Physical Evidence • Provides a tangible object for the jury to see • Can be taken into the jury room • The defendant cannot distort the physical evidence. • Some cases cannot be solved without the physical evidence • Physical evidence is not subject to memory loss • The defendant can have the evidence tested by an independent expert.

  6. Evidence- anything that can be used to determine whether a crime has been committed. Materials collected and scientifically analyzed to determine the nature and circumstances of a crime. Direct-establishes a fact (eyewitness) Circumstantial- provides an inference about what happened (more reliable than direct) • COMPARISON • Subjecting a suspect specimen and a standard (reference) specimen to the same tests and examinations for the purpose of determining whether or not there is a common origin. Does it Match? • IDENTIFICATION • To determine the physical or chemical identity of a substance with as near absolute certainty as existing analytical techniques will permit. What is it?

  7. It is imperative to conduct a thorough collection and scientific evaluation of physical evidence for all criminal investigations.Physical evidence can be used to link an individual to a crime or to exonerate a person from suspicion. • Common Types of Physical Evidence: (Reconstructive vs. Associative) • Blood, Semen, and Saliva (B) - Impressions (P) • Documents (P) - Organs & Body Fluids (B) • Drugs (P) - Paint (P) • Explosives (P) - Petroleum Products (P) • Fibers (P) - Plastic Bags (P) • Fingerprints (P) -Plastic, rubber, & polymers • Firearms and Ammunition (P) - Powder Residues (P) • Glass (P) - Serial Numbers (P) • Hair (B) - Soil & Minerals (P) • Tool Marks (P) - Vehicle Lights (P) -Wood and plant matter (B)

  8. Class Characteristics Properties of evidence that can only be associated with a group and never with a single source. The “product rule” is often used to calculate the overall frequency of an occurrence in a population. (multiply the frequencies of independently occurring genetic markers) Individual Characteristics Properties of evidence that can be attributed to a common source with an extremely high degree of certainty or probability. Physical Evidence Characteristics The practical and personal experience of the examiner supports or negates the significance of these evidence characteristics.

  9. Class Characteristics • Creation and updating of databases • Can corroborate events, eyewitness accounts, confessions, and informant testimony • Must be free of human error and bias • Must exhibit a significant amount of diversity When do class characteristics become individual characteristics?

  10. Individual Characteristics • Criteria somewhat subjective • More specific and detailed • Sophisticated techniques and improved technology have minimized the limits of identification. • Could become too particular that they could negate identification of evidence from its source due to natural variations.

  11. Presumptive Tests Identify suspect evidence (class) Cheaper Faster Can be done at crime scene Less training needed Help focus investigation Specific Tests Can lead to individual classifications Costly Time consuming Typically done in the lab More exact procedure Match a suspect to a crime Identifying Physical Evidence

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