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Lecture

ANT205 - Oct 31 (Time Since Death).docx

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Department
Anthropology
Course
ANT205H5
Professor
Carolan Wood
Semester
Fall

Description
Forensic video - Death - Fresh o Rigor mortis - Bloated o Bloating of abdomen o Increased odor o Marbling of skin o Skin slippage on extremities o End when perforation of insect activity - Active decay o Enhanced insect activity o Deflation of body activity o Wet appearance o Odor is strong o Loss of body mass (-50%) - Advanced decay o Corpse dry out o Insects prepare to migrate away o Most flesh has been removed o Odor begins to fade - Dry stage o Initial insects have migrated o New insect species arrive o Bones, skin, hair, teeth, cartilage o Odor is negligible - Remains o Continuation of dry stage o Mainly just bones and teeth, not much skin left o Odor is faint or absent - If body is buried, the timeline would be longer than a body sitting on the surface - Aquatic burial elongates the timeline as well, and the bloated stage makes the body float - Increased the speed of timeline is in very humid conditions - Trauma to body makes the insects more attracted - Substrate (ground or concrete) - Rain - Scavenging o Broken in parts to accelerate decomposition - Covering o Maggots don’t like direct sunlight so it has a higher activity level if it’s under a covering - Soil pH o Acidic environment can dissolve human bones entirely Time since Death Lecture - Time since death o Importance  Identification  Testing alibis  In the case of forensic anthropology, you are not going to get very specific times o 3 methods o Corporal  Decomposition (based on the body itself) o Environmental  Insects, leaf layers  Roots, artifacts (Roots grown in and through remains? Clothing decay) o Habitual activities of victim o The date that the individual went missing does not denote the date of death - Early decompositional stages o Forensic pathologist o Autolysis  Destruction of tissues by enzymes o Putrefaction  Reduction and liquefaction of tissue by bacteria  Consumption of body tissue by internal bacteria (the body eating itself = autolysis) o Affected by environment o Temperature  When body is outside o Humidity  Water vapour in the air o Soil conditions  pH level o Light  Related to insects, flies don’t like to lay eggs in light, they like dark places o Exposure to wind, water and snow o Burial conditions  Depending on how far the body was buried o Presence/absence of clothing o Trauma and pre-existing disease  Ex. Fever means the body temp is already elevated so body decomposes faster - Algor mortis – body cooling o Dead bodies cool to ambient temperature  Internal temp o Rate influenced by factors listed previously o Coverings slow rate of cooling  Fat body loses heat slowly (fat is insulation) o Estimate elapsed time since death  Compare temperature of corpse to ambient temperature  Bodies do not cool at consistent rate - Using body temperature to determine time since death o Average adult corpse loses heat  1.5 degree F per hour in temperate climates  0.75 degrees F per hour in tropical climates o Useful up to 18 hours after death depending on environmental conditions - Liver mortis – discolouration o Blood drains to low parts  Ex. Body hanging by the neck, the blood drains to feet o ½ to 4 hours post mortem o Peaks at 8-12 hours  Once it becomes fixed, it can no longer be used for PMI o Time since death o Position of the body o Low points – skin purple o Pressure points – white o Pattern formed when individual dies is retained  Even if the body moved - Rigor mortis – stiffening o Rigor mortis  Limited by very short amount of time and complicated with people with very dark skin so you can’t see the differences as clearly o At death, muscles relax  Lower jaw drops  Eyelids lose their tension  Muscles are soft  Joints are flexible o Muscle glycogen converted into lactic acid  pH drops o as muscle becomes acidic  a constituent coagulates o stiffening of the limbs and body o putrefaction increases pH  coagulant liquefies  body becomes flaccid o rigor begins in the eyelids and face 1-4 hours post mortem o peaks at 6-12 hours post mortem o 24-36 hours, rigor begins to leave the body - Later decompositional stages o Blue-green discoloration of lower abdomen (24 hours)  Bacteria and enzymes migrate from the bowel to the body tissue o Spr
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