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Lecture 21: Glass : A Multitasking Class of Evidence.

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Presentation on theme: "Lecture 21: Glass : A Multitasking Class of Evidence."— Presentation transcript:

1 Lecture 21: Glass : A Multitasking Class of Evidence

2 Direction & Sequencing Through a Windshield

3 Bullet though a windshield Passes through first pane, the laminate and the second pane before exiting Laminate changes dynamics Restricting usual bending movement of glass and altering the visual shape of the cone on exit side of the glass. Two cones form. Different subtle visual characteristics that can be identified at the scene. Direction Through A Windshield

4 Sequencing Laminated Glass Two Layers of Glass With Plastic Laminate Between

5 Identify intersecting radial fractures Determine which were stopped by the radial fractures. Shots into laminated windshield glass gives fractures on both sides of the laminate. Track only fractures on one side of the glass to find intersecting fractures Be wary of artifacts from movement of the car or from the laminate … consider as part of shot sequence. Shot Sequence in Laminated Windshield

6 Crater Sequence? Laminated Windshield Hard Edge Hard edge of bullet hole (arrow) is visible. This is an indication that the bullet was moving from the outside to the inside of the vehicle.

7 Understanding Distribution of Glass Shards Double pane basement window Direction Of Force

8 Collecting and Preserving Glass Evidence The first step in preserving glass evidence is to understand how it fractures and the distribution it can take at the scene, which depends largely on the type of break.

9 Purpose: Capture & preserve patterns … Tempered glass with bullet holes is fragile … tape both sides to prevent mass of glass nuggets during transit. It could shatter even after taping. Capturing intact pattern; Photograph properly before glass falls apart Photograph entire patter of fragments On ground/in vehicle, etc Archiving Glass Evidence Photography/Video/Sketching

10 Operative rule for collecting, packaging and preserving glass evidence is Common sense … Understanding the type of break. Objective: Prevent alteration of the evidence during packaging and transit. Care when collecting the evidence so that damage does not occur … the scene before packaging. Mark the interior and exterior sides of glass, Before packaging ID direction of the force, if Tape the edges of glass for safety and evidence protection. Label the larger, outer container GLASS FRAGILE and case identification information. Collecting, Packaging and Preserving Glass Evidence

11 Large Pieces: Place between pieces of rigid cardboard & tape the cardboard sides together. Place taped cardboard into larger container & secure to prevent movement. Small shards Place in proper container, Glass vial or small cardboard box Do not allow shifting during transit. Collecting and Preserving Glass Evidence

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