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JS 113 Forensic Science Slides by Jeremiah Garrido SCCCL

Laboratory II Footwear impression laboratory. JS 113 Forensic Science Slides by Jeremiah Garrido SCCCL. Forensic Significance of Footwear Impressions.

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JS 113 Forensic Science Slides by Jeremiah Garrido SCCCL

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  1. Laboratory II Footwear impression laboratory JS 113 Forensic Science Slides by Jeremiah Garrido SCCCL

  2. Forensic Significance of Footwear Impressions • Whether on hard or soft surfaces, the direct physical contact between the shoe and the substrate (surface) results in a transfer of class and individual characteristics from the shoe to the impression it leaves • Two-Dimensional Impression • Three-Dimensional impression

  3. Two-Dimensional Impressions • As people walk about different they can acquire dust, dirt, residues, grease, oil, blood, and moisture onto shoes • The shoes then deposit these materials back onto other surfaces they subsequently track over

  4. Three-Dimensional Impressions • Walking over surfaces such as sand, soil, or snow, they may cause permanent deformation of that surface

  5. Class and Individual Characteristics Class and individual characteristics are examined to determine if a specific item of footwear made the questioned crime scene impression, or if that item can be eliminated.

  6. Detection and Recovery of Footwear Impressions • The primary consideration for collection of impressions is for preservation and its reproduction for later examination by the crime lab • Before any impression is moved or handled it must be _______________ with a scale • Several shots should be taken over the impression with use of a Tripod and at different angles around impression with appropriate side lighting

  7. Detection and Recovery of 2-Dimensional Footwear Impressions • Electrostatic Lifting-utilizes high-voltage power source to create a static electrical charge that allows the transfer of a dust impression from the surface to a special black lifting film (mylar) • Adhesive or Gelatin Lifting-the impression may be enhanced with fingerprint powder and lifted with a gelatin or adhesive lift. • You will be performing adhesive test lifts on the three boots that may have been involved in the crime and comparing them, as footwear examiners, to a three-dimensional impression from the crime scene.

  8. Detection and Recovery of 2-Dimensional Footwear Impressions • Prints in blood • Chemical enhancement • Can still obtain DNA results • LCV-Leucocrystal Violet • Amido Black Faint & Diluted Bloodstain

  9. Detection and Recovery of 3-Dimensional Footwear Impressions • All three-dimensional impressions should be cast with dental stone. Dental stone is like plaster but sets much harder and has a higher compressive strength. • Snow?

  10. What About Impressions in Snow ?

  11. Application of Snow Print Wax Casting with dental stone Collect & submit Cast to lab Inscribe case info & initials

  12. Investigative Info Information Footwear Impressions may provide (see lab handout) • Identification of Footwear- class and individual characteristics • Elimination of Footwear- • Participation in the Crime- • Location of Impression • Rebuttal or Confirmation of Suspects Alibis- • Determination of Shoe Brand- • Linking scenes of Crime- • Shoe Size- • Association with other evidence- • Gait Characteristics- • Tracking-

  13. Lab Exercise: CRIME SCENE • During a heavy rainstorm in a large city in the Northeast, a convenience store owner was robbed and murdered in a similar manner to several prior robbery-homicides. The assailant quickly entered the store, pointed the gun at the victim’s head and shot him. The assailant then jumped over the counter and emptied the cash register. As the assailant left the store, police pursued him on foot. The long chase, through the storm, led through buildings and parks and over flat-topped roofs. The police backtracked the prints to a city park where he had hidden momentarily. In this covered area they found the gun. Next to the gun were several shoeprints of the same design. All of the shoeprints were photographed. • Three individuals that fit the description of the suspect were brought in for questioning. Police observed that ALL three individuals were wearing the same brand shoe, which appears to have possibly deposited the shoeprints at the scene. Therefore, the shoes from these individuals were submitted to the crime lab for examination.

  14. Objective 1: Make a Known Test Impression of Footwear Submitted • Using paper & fingerprint powder • Produce a highly detailed sample of the class and individual characteristics of the shoes. • Test impression will be compared to CS 3-D impression (cast)

  15. Objective 2: Make a Cast of One of the Impressions at the crime scene to compare to the Known Test Impressions taken in Objective One After completing your objectives, using individual characteristics, identify which shoe submitted to the laboratory deposited the impression at the crime scene

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