NOVEMBER 15, 2013 EQ: What techniques are used in Forensic Science to analyze glass? You DO NOT need your composition books for the warm-up today. WARM-UP: Today we will have a “HAIR CHALLENGE” in which you and a partner will observe several microscopic pictures of hair. You must identify the origin of each hair and write it down on the paper that will be given to you.

OCTBER 1, 2015 EQ: HOW IS GLASS ANALYZED TO SOLVE CRIMES? WARM-UP: (Write the questions & answer the questions while watch the following the video.) What are the names of the Central Park Five? Were they innocent of committing any crimes? Why do you think they confessed to raping the victim? What role did the media play in how they presented the story?

MARCH 14, 2016 EQ: HOW IS GLASS ANALYZED TO SOLVE CRIMES? WARM-UP: Case 004 Make as many observations about the crime scene on the next slide and be prepared to answer questions about the crime scene.

What do you think happened? Crime Scene 004 Study this crime scene. What do you think happened?

Crime Scene 004 What happened… Detroit, Michigan (January 2009) Dead body in elevator shaft of abandoned building Body is frozen in 2-3 feet of ice Finder playing ice hockey in basement What actually happened has not been reported

What do you think happened? Crime Scene 004 Study this crime scene. What do you think happened?

Forensic Analysis of Glass:

Glass Hard, brittle, amorphous substance composed of sand mixed with various metal oxides Links a suspect at the scene of a crime *Amorphous-(atoms or molecules are arranged in random or disordered positions)

TEMPERED GLASS Glass to which strength is added by introducing stress through rapid heating and cooling of the glass surfaces When it breaks it does not shatter, but fragments or “dices” into small squares with little splintering Ex. side and rear windows of cars

LAMINATED GLASS Two sheets of ordinary glass bonded together with a plastic film Ex. Windshields of U.S. cars

Which type of glass dices into pieces when it breaks?

Rolled Glass Float Glass Float Glass Process

DENSITY =MASS/VOLUME Flotation Method: standard/reference glass is immersed in bromoform and bromobenzene and bromo. is added until the glass floats glass density=liquid density

Refractive Index: When 2 substances have different RI, light passing through them produces a Becke Line

https://www.youtube.com/watch?v=qH1S83Bkttw

The Becke line disappears- medium and fragment have similar Immersion Method glass particles are immersed in a liquid whose refractive index is adjusted until it equals that of the glass particles (match point) A Becke line- a bright halo observed near the border of a particle immersed in a liquid (usually silicon oil) of a different refractive index The Becke line disappears- medium and fragment have similar refractive indices

Which method uses the density of a reference glass to determine the density of the unknown sample?

Use the following words to create 2-3 related sentences. WORD SPLASH!!!! Use the following words to create 2-3 related sentences. Becke line Flotation method Immersion method Density Laminate glass Tempered glass Refractive index

Frayer Models: Laminate Glass Becke Line Tempered Glass Flotation Method Immersion Method Definition Definition in your own words Picture Example

Color, diameter, striations, pitting of fibers, cross-sectional shape MARCH 15, 2016 EQ: HOW CAN GLASS FRACTURES BE USED TO ANALYZE A CRIME SCENE? WARM-UP: (Write the questions & answers) What is the name of the structure from which hair grows? Name (2) characteristic used to identify synthetic fibers. What type of glass is used on the rear window of cars? follicle Color, diameter, striations, pitting of fibers, cross-sectional shape tempered

GLASS DATABASES: Glass databases using the refractive indices (RI)

Populations of Glass RIs

Glass bends in response to any force exterted on it’s surface

Direction of Penetration A projectile hole is inevitably wider at the exit side bsapp.com

Direction of Penetration 1. Radial 2. Concentric bsapp.com

How does Glass break? Forensic Fracture Analysis

Radial Begin at a point and radiate outward from point of impact -initial crack is on the side opposite the applied force

Concentric Motion of the projectile through the glass puts tension on the front surface of the glass, causing concentric fractures. -the exit hole helps to determine the direction on impact.

Fractures Concentric Radial bsapp.com

Which glass fracture occurs first upon impact? Radial

Stress Marks Radial Cracks-the perpendicular edge of stress marks is always found opposite the side where the force was applied bsapp.com

Concentric Fractures: (opposite of radial) The perpendicular end always faces the surface on which the force originated

Direction of Penetration 1. Radial 2. Concentric bsapp.com

3R Rule: Radial cracks form a Right angle on the Reverse side of the force.

Which type of crack forms right angles on the opposite side of where the force was applied? Radial cracks

Counting Bullet Holes Determination of the sequence of bullet holes can be made by noting the radial fractures. Radial fractures caused by the passage of a bullet stop at pre-existing fracture.

Successive Penetrations A fracture always terminates at an existing line of fracture bsapp.com

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How much glass should be collected at a crime scene? ALL!!!

Submit all glass evidence found on suspect and at the crime scene What must an evidence collector do when an individual fit of glass pieces is not possible? Submit all glass evidence found on suspect and at the crime scene

Individually wrapped in paper Suppose a suspect’s shoes/clothing has glass, how should it be packaged? Individually wrapped in paper

When you are finished gluing your fractures, explain fractures using the following terms: Radial fractures Concentric fractures Stress marks Force applied Perpendicular edge

Cut out the bullet hole and remaining glass pieces and swap glass pieces with someone and glue them to your paper. Label: Radial Fracture Concentric Fracture

the hole would be smaller on the entrance side OCTOBER 5, 2015 EQ: How is glass analysis used to solve crimes? WARM-UP: Write and answer the following questions. When you’re done start reading the lab procedures. Which type of crack occurs on the opposite side of the force applied? Which type of crack occurs after the first and is circular in shape? How can you tell which side of the glass the object hit first? radial concentric the hole would be smaller on the entrance side