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Forensic Science

Forensic Science. Unit 4B Day four. Today’s agenda. Due today: Using medical terminology 2. Diagramming Injuries worksheet Work for Today: Insect Evidence collection video Flying Clocks lab- lab is in the lab area. What are the stages of decomposition?. One day old pig.

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Forensic Science

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  1. Forensic Science Unit 4B Day four

  2. Today’s agenda • Due today: • Using medical terminology 2. Diagramming Injuries worksheet Work for Today: Insect Evidence collection video Flying Clocks lab- lab is in the lab area

  3. What are the stages of decomposition?

  4. One day old pig One day old dead pig showing signs of skin changes and bloating

  5. One week old pig Advanced stages are seen in one week old dead pig. As the larva develop they migrate from the body and develop into pupa

  6. What is the order of decay? • Autolysis: nonbacterial; release of gases • Putrefication: slippage of skin, etc. • Necrophagus arthropods: arrival depends on: -Season or climate -Situation of corpse (open air, buried, water, geographic location; cause of death, degree of mutilation) Changes in skin by decomposition

  7. What is the effect of temperature on decomposition? • Ambient heat plays a role during egg and early larval development • After that, its effect decreases rapidly • Maggot masses generate their own heat Taking temperature of the maggot mass can find it as high as 125 degrees

  8. What is PMI? • PMI: Postmortem Interval • An estimation of the duration of PMI involves setting the minimal and maximum time between death and corpse discovery • Important in narrowing the field of suspects • The minimal PMI is determined largely by estimating the age of developing insects collected at time of corpse discovery • The maximum PMI is determined from species of insects that are present and the weather conditions necessary for specific activity of these species

  9. When heart stops, the body turns pale and looks waxy Blood settles & discolors to purplish red. Eyes flatten; extremities turn blue Appearance of burning shows up on drying mucous membranes Body putrefies, turning greenish in color. Bacteria grows & accumulates 5. Rot spreads & a foul odor develops. Body bloats due to bacterial producing gases in intestines Skin blisters from gases, detaches from muscles and bursts. Top layers peel off. In some circumstances, a cheesy substance called “adipocere” forms as fatty tissues harden What body changes occur due to Decomposition? Left alone in a warm/moist climate, a body can decompose to a skeleton within a few weeks. In other conditions it can take months or even years.

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