Back in the day … 17 th century: anyone in a coma or with a weak heartbeat was presumed dead & buried fear of being buried alive = cowbell in coffin (“saved by the bell”?) “waiting mortuaries”
Death is … … cessation (end) of life? … “irreversible cessation of blood circulation”? … cessation of all brain activity? hard to give a single definition of – it is a PROCESS rather than an instant event
1 st stage of death: STOPPAGE heart stops cells begin to die (no O 2 ) body processes fail (no O 2 ) nerves, muscles, organs, brain fail autolysis: cell breakdown
Manner of Death (MOD) natural death (most common) - interruption/failure of body functions from age or disease accidental death - unplanned events (car accident, falling from a ladder) suicidal death - person purposefully kills oneself homicidal death - death of one person caused by another undetermined
Cause of Death (COD) the reason someone dies is the COD disease, physical injury, stroke, heart attack, bludgeoning, shooting, burning, drowning, strangulation, hanging, suffocation, etc. “proximate cause of death” is an underlying cause (as opposed to the final cause)
Mechanism of Death the specific body change that brought about cessation of life ex: if COD is shooting, mechanism may be blood loss (exsanguination) or loss of brain function ex: if COD is a heart attack, mechanism may be heart stopping to beat or pulmonary arrest
Time of Death (TOD) many factors are used to estimate TOD
Livor Mortis literally means DEATH COLOR RBC break down & spill contents hemoglobin turns purple when it spills purplish color visible wherever blood pools (lividity)
Livor Mortis 2 hrs after death: lividity begins 8 hrs after death: discoloration permanent between 2 and 8 hrs after death: if you press skin, discoloration disappears ambient temp affects time for lividity to set in (hotter = faster) can reveal approximate TOD and position of corpse and if they’ve been moved (dual lividity)
Rigor Mortis literally means DEATH STIFFNESS temporary
Rigor Mortis no visible rigor: 48 hrs very rigid (full rigor): ~12 hrs rigor only in face & neck: just over 2 hrs some rigor in body, none in face: more than 15 hrs ago
Rigor Mortis stiffness occurs because skeletal muscles can’t relax (they are contracted) due to presence of extra calcium muscles control bone movement so joints appear to be rigid too
Rigor Mortis factors that affect rigor mortis include: - ambient temp (warmer = faster due to faster chem reactions) - body weight (thinner = faster due to less stored O 2 ) - type of clothing (clothed = faster) - illness (sick/fever = faster) - level of activity before death (aerobic exercise = faster) - sun exposure (sunlight = faster)
Algor Mortis literally means DEATH HEAT temperature loss generally, - lose 1.4 o F per hour for the first 12 hrs - lose 0.7 o F per hour after 12 hrs until body reaches temp of surroundings
Stomach & Intestinal Contents also used to help determine TOD 4-6 hrs for stomach to empty contents into small intestine another 12 hrs for food to leave small intestine 24 hrs for all undigested food to be released
Stages of Decomposition within 2 days - cell autolysis - green/purplish staining - marbled skin - discolored face after 4 days - skin blisters - abdomen swells with CO 2 within 6 to 10 days - corpse bloats with CO 2 - chest/abdominal cavities burst and collapse - fluids leak from body openings - eyeballs/other tissues liquefy - skin sloughs off
Forensic Entomology Flies arrive within 10 minutes of death Type of insects follows a succession as the body undergoes changes from- The fresh stage, to the bloating stage to the dry or skeletal stage when the skin falls of leaving teeth and bone
Four development stages of flies: egg Hatch into a larva or maggot crawls like a caterpillar and actively consumes food to grow quickly. Maggots will pass through several instars or stages – keep getting bigger and molt at end of every stage Next stage: a dark immobile pupa.
adult fly emerges from pupa Adults mate, and the females will lay more eggs onto corpses. Lays eggs in natural body openings Eggs/ worms in head area first Then reproductive/ excretory regions Trunk at very late stage
Insects are ectothermic-body needs to be warmed by outside to be able to grow Will speed up process in hot climates/slow in cold regions Drugs – cocaine will speed up life cycle Drugs – poisons (arsenic) will slow down
Order of flies Blow flies and flesh flies – arrives in 10 minutes Blow flies will lay eggs on corpse on day 1 Will see maggots by day 2
Image: http://www.umext.maine.edu/images/FlyLife.jpg Information: http://www.kathyreichs.com/entomology.htm and http://www.forensicentomologist.org/ Blow Fly Metamorphosis 1st – Adult flies lay eggs on the carcass especially at wound areas or around the openings in the body such as the nose, eyes, ears, anus, etc. 2nd – Eggs hatch into larva (maggots) in 12-24 hours. 3rd– Larvae continue to grow and molt (shed their exoskeletons) as they pass through the various instar stages. 1st Instar - 5 mm long after 1.8 days 2nd Instar - 10 mm long after 2.5 days 3rd Instar – 14-16 mm long after 4-5 days 4th – The larvae (17 mm) develop into pupa after burrowing in surrounding soil. 5th – Adult flies emerge from pupa cases after 6-8 days. Blow flies are attracted to dead bodies and often arrive within minutes of the death of an animal. They have a complete life cycle that consists of egg, larva, pupa, and adult stages. It takes approximately 14-16 days from egg to adult depending on the temperatures and humidity levels at the location of the body. Adult Eggs Pupa 3 rd Instar Larva 2 nd Instar Larva 1 st Instar Larva
Flesh flies will deposit maggots on corpse on day 1 Day 1-3 protein and carbs
House flies come after the flesh fly and blow fly Will lay eggs by day 2 and maggots will be seen by day 4
The next fly to follow ONLY IN URBAN areas is the skipper fly Will lay eggs by day 5; maggot by day 7
Predatory flies appear next to feed on the flies, NOT ON THE CORPSE These are beetles, wasps etc
Fresh stage 0-3 days Protein, carbs break down - Blows flies and flesh flies - no smell yet Bloated stage- 3-7 days Decay starts- smell starts- abdomen bloats due to CO2 made by bacterial respiration House flies and predatory flies
Decay stage (putrid smell due to gas release) 8-18 days – total decay- all body bloats; abdomen breaks down – fluid seepage Ants, cockroaches, beetles Over 18 days – drying out phase; flesh falls off; worms not present Mainly bugs that can feed from bones such as beetles.
Examples of Diptera (Flies) Informational Source: http://naturalsciences.org/files/documents/csi_tg_overview.doc Images: Top Left - http://www.scienceinschool.org/repository/images/issue2forensic3_large.jpg, Middle-Left: http://forensicfact.files.wordpress.com/2008/04/blowfly053.jpg, Top Right - http://users.usachoice.net/~swb/forensics/P1.jpg, Bottom - http://www.deathonline.net/decomposition/corpse_fauna/flies/index.htm Flesh Fly (Sarcophagidae) S triped thorax Blow & Greenbottle Flies (Calliphoridae) Metallic thorax and abdomen House Fly (Muscidae) Cheese Skipper (Piophilidae) Early Stage Decomposition Late Stage Decomposition Life Cycle of a Calliphoridae Fly
Examples of Coleoptera (Beetles) Informational Source: http://naturalsciences.org/files/documents/csi_tg_overview.doc Images: http://www.cals.ncsu.edu/course/ent425/library/spotid/coleoptera/coleoptera.html & http://www.forensicflies.com/beetles.htm Carrion Beetles ( Silphidae) Adults & larvae feed on fly larvae Early to Late Stage Decomposition Late Stage Decomposition Rove Beetles (Staphylinidae) Predator of fly eggs Early Stage Decomposition Hide Beetles (Scarabidae) Usually the last to arrive Clown Beetles (Histeridae) Predator of fly eggs Ham & Checkered Beetles (Cleridae) Predator of flies & beetles; also feed on dead tissue Skin Beetles (Dermestidae) Feed on dried skin & tissues
Weather data is also an important tool in analyzing insect evidence from a corpse. Investigators will make note of the temperature of the air, ground surface, the interface area between the body and the ground, and the soil under the body as well as the temperature inside any maggot masses. They will also collect weather data related to daily temperature (highs/lows) and precipitation for a period of time before the body was discovered to the time the insect evidence was collected. Other factors that might affect their PMI estimates: 1.Was the body enclosed in an area or wrapped in a material that would have prevented flies from finding the corpse and laying eggs? 2.Were other insect species present that may have affected the development of the collected species? 3.Were there drugs or other poisons in or on the body that might have affected the larvae’s development? Did you know… The “Body Farm” in Knoxville, Tennessee is a university research facility to investigate human decomposition under various conditions in order to understand the factors which affect its rate. Click the image to view a video about the Body Farm!
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