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Forensics

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    Forensics Forensics Presentation Transcript

    • Unit 4
      Revision
      Forensic Science
    • What clues does a dead body leave behind?
    • 1. Extent of decomposition
    • 2. Extent of rigor mortis
    • 3. Temperature
    • 4. Entomology
      Which insects (usually fly larvae) are living in the dead tissue
      What stage of development have they reached
    • What clues does a dead body leave behind?
    • Why brain cells stop functioning immediately after death?
    • How does rigor mortis takes place?
      Muscle cells have large stores of ATP and glycogen and can continue to respire anaerobically for some time after death.
      ATP is needed to maintain the muscles in a relaxed state.
      As the muscle cells run out of ATP, the muscle fibres become permanently contracted and lock solid.
      This produces a stiffening effect which is known as rigor mortis.
      On average, rigor mortis starts about 2-4 hours after death
      It needs between 6 and 8 hours to take full effect.
      It begins in the muscles in the face and neck, progresses down the body, and spreads steadily to the larger muscles of the body.
    • How quickly rigor mortis can sets in?
      Rigor mortis depends on the level of ATP in muscles at the time of death.
      The level of ATP varies from person to person depending on
      · genetics
      · level of fitness.
      ·level of activity before death.
      For example, rigor mortis usually sets in very quickly in drowning victims. because they have used up all their muscle ATP struggling to stay afloat.
    • Rigor mortis is also affected by the temperature of the surroundings.
      Rigor mortis is not permanent — it usually passes between 36 and 48 hours after death.
      The muscles soften as enzymes released from the lysosomes begin to break down the tissue.
    • To secure a prosecution for murder, a number of facts need to be verified.
      • Who died, and who killed them.
      • What was used to commit the crime.
      • When the victim died.
      • Where the murder took place.
      • Why the murder took place — the motive for the crime.
    • Temperature
      Normal human body temperature is 37o C.
      The metabolic reactions stops after death.
      Heat is transferred from body into the surroundings by radiation, conduction and evaporation of water.
      The decrease in temperature gives an idea about the time of death.
    • Factors affecting body temperature
      Outside of the body cools much more rapidly than the inside.
      The amount of body fat in the dead person affects the rate of cooling because it acts as insulation.
      Clothing in the dead body will have an effect in losing temperature.
      The immediate surrounding of the body can also affect temperature loss.
    • Cooling curve for bodies under known conditions are available.
      From analyzing these curves and comparing it with the dead persons data, it is possible to estimate the time of death.