The Meaning, Manner, The Meaning, Manner, Mechanism, Cause, and Time of Mechanism, Cause, and Time of

DeathDeath►Death:Death: the irreversible cessation of the irreversible cessation of

circulation of blood; the cessation of all circulation of blood; the cessation of all brain activity.brain activity.

►Death is not an instant event, it is a Death is not an instant event, it is a process. This makes it difficult to process. This makes it difficult to pinpoint the exact moment that someone pinpoint the exact moment that someone dies.dies.

The Manner of DeathThe Manner of Death

►4 ways a person can die:4 ways a person can die:►Natural deathNatural death►Accidental deathAccidental death►Suicidal deathSuicidal death►Homicidal deathHomicidal death

►Undetermined deathUndetermined death

Cause & Mechanism of Death

►Proximate COD vs. Final CODproximate is the underlying COD; if a

person is exposed to radiation and then develops cancer and dies…the proximate COD is the radiation exposure, the final COD is cancer

►Mechanism of Deathspecific change in the body that

brought about the cessation of life (exsanguination, cessation of brain function, or the heart stops beating)

Determining Time of Death

►Livor MortisMeans ‘death color’ (literal Latin

translation ‘bruise of death’). As red blood cells break down, the blood pools on parts of the skin causing a discoloration.

Pooling of the blood is called lividity, and it provides clues as to how long the person has been dead.

Lividity first becomes visible about 2 hrs. after death; discoloration becomes permanent after 8 hrs. (coloring won’t disappear when skin is pressed)

►Livor mortis will not be present where clothing or accessories (belts, watches) restricted blood flow.

►The ambient temperature can also impact lividity. It takes place faster in hotter weather than in colder weather.

►Livor mortis gives clues as to how the corpse was positioned within the first 8 hrs. after death. Forensic pathologists can determine if a corpse has been moved if the livor mortis does not match up with the location it was found in.

Rigor Mortis

►Literally means ‘death stiffness’. It is temporary and can be useful in determining time of death.

►Starts within 2 hrs. of death-begins in the head and works its way down to the legs.

►After 12 hrs., the body is in its most rigid state.►Stiffness gradually disappears after 36 hrs.►Depending on body weight and ambient

temperature, rigor may remain for as long as 48 hrs.

Factors Affecting RigorAmbient temperature Cooler the body, slower

the onset of rigor

Person’s weight Thinner individuals will experience rigor faster

Type of clothing Warmer clothes speed up rigor mortis

Illness Fever vs. hypothermia changes onset of rigor

Level of physical activity shortly before death

Causing an increase or decrease in body temp.

Sun exposure Causing an increase or decrease in body temp.

Algor Mortis►Literally means ‘death heat’ (literal Latin

translation ‘chill of death’) and describes the temperature loss in a corpse.

►Forensic investigators measure liver temperature in order to determine temperature of the corpse.

►Approximately 1 hr. after death, the body cools at a rate of 0.78°C per hour.

►After the first 12 hrs., the rate drops to 0.39°C until the corpse reaches the same temp. as its surroundings.

►This is just an estimate and should not be used as the sole determination in time of death!!!

Stomach & Intestinal Stomach & Intestinal ContentsContents

►Usually takes 4-6 hours for the Usually takes 4-6 hours for the stomach to empty its contents into the stomach to empty its contents into the small intestinesmall intestine

►Another 12 hours afterwards for the Another 12 hours afterwards for the contents to leave the small intestinecontents to leave the small intestine

►Approximately 24 hours from when a Approximately 24 hours from when a meal was eaten until all undigested meal was eaten until all undigested food leaves the bodyfood leaves the body

Changes of the EyeChanges of the Eye

►The surface of the eye dries; a thin film The surface of the eye dries; a thin film appears within 2-3 hrs. if eyes were appears within 2-3 hrs. if eyes were open at t.o.d., within 24 hrs. if eyes open at t.o.d., within 24 hrs. if eyes were closed/covered.were closed/covered.

►Potassium accumulates inside the Potassium accumulates inside the vitreous humor (clear gel that fills space vitreous humor (clear gel that fills space between the lens and the retina)between the lens and the retina)

DecompositioDecompositionn

►Within 2 days after death, cell autolysis begins Within 2 days after death, cell autolysis begins following death, green & purplish staining following death, green & purplish staining (bruising), skin looks marbled, the face (bruising), skin looks marbled, the face becomes discoloredbecomes discolored

►After 4 days, the skin blisters, abdomen swells After 4 days, the skin blisters, abdomen swells as COas CO22 is released by bacteria in intestine is released by bacteria in intestine

►Within 6-10 days, corpse continues to bloat Within 6-10 days, corpse continues to bloat until chest & abdominal cavity burst & collapseuntil chest & abdominal cavity burst & collapse

Most Important Environmental Most Important Environmental Factors in Corpse Decay*Factors in Corpse Decay*

►TemperatureTemperature►Access by insectsAccess by insects►Depth of BurialDepth of Burial

► * Based on study of decay rates of 150 human * Based on study of decay rates of 150 human corpses at U. of Tenn.corpses at U. of Tenn.

Ecological Roles of Insects in Ecological Roles of Insects in DecompositionDecomposition

► Necrophages – species feeding on corpse Necrophages – species feeding on corpse tissue; mostly true flies and beetles; age tissue; mostly true flies and beetles; age determination (larval instar) important for PMIdetermination (larval instar) important for PMI

► Omnivores – insects that feed both on the Omnivores – insects that feed both on the corpse and associated fauna; ants, wasps and corpse and associated fauna; ants, wasps and some beetles; may alter rate of some beetles; may alter rate of decomposition decomposition

► Parasites and Predators – many beetles, true Parasites and Predators – many beetles, true flies and wasps that attack immature fliesflies and wasps that attack immature flies

► Incidentals – use the corpse as a resource Incidentals – use the corpse as a resource extension; springtails, spiders, centipedes, extension; springtails, spiders, centipedes, some mitessome mites

Generalized Fly Life CycleGeneralized Fly Life Cycle► Eggs Eggs ► Approx. 2mm long.Approx. 2mm long.► present in clumps of up to 300 present in clumps of up to 300 ► laying to hatching takes 1 day laying to hatching takes 1 day

► Larva - 1st instar Larva - 1st instar ► Approx. 5mm longApprox. 5mm long► initially feeds on fluid exuded from initially feeds on fluid exuded from

the body the body ► migrates into body migrates into body ► hatching to first molt takes 1 day hatching to first molt takes 1 day

► Larva - 2nd instar Larva - 2nd instar ► Approx. 10mm longApprox. 10mm long► moves around in maggot mass moves around in maggot mass ► first molt to second molt takes 1 first molt to second molt takes 1

day day

► Larva - 3rd instar Larva - 3rd instar ► Approx. 17mm longApprox. 17mm long► still moves in mass still moves in mass ► second molt to pre-pupa takes 2 second molt to pre-pupa takes 2

days days

Generalized Fly Life Cycle Generalized Fly Life Cycle cont.cont.

► Pre-pupa Pre-pupa ► Approx. 9mm longApprox. 9mm long► migrates away from the corpse seeking a suitable pupation site migrates away from the corpse seeking a suitable pupation site ► does not feed does not feed ► transforms into pupa transforms into pupa ► pre-pupa to pupa takes 4 days pre-pupa to pupa takes 4 days

► Pupa Pupa ► Approx. 9mm long and light to dark brownApprox. 9mm long and light to dark brown► resides within puparium resides within puparium ► undergoes transformation from larval body form adult fly undergoes transformation from larval body form adult fly ► does not feed does not feed ► pupa to emergence takes 10 days pupa to emergence takes 10 days

► Adult fly Adult fly ► mates on emergence from pupa mates on emergence from pupa ► feeds on protein from body fluids feeds on protein from body fluids ► lays eggs on corpse lays eggs on corpse ► emergence to egg laying takes 2 days emergence to egg laying takes 2 days

Initial decay - 0 to 3 days Initial decay - 0 to 3 days after deathafter death

► From the moment of death flies are attracted to bodies.From the moment of death flies are attracted to bodies.► Bacteria and the body's own digestive enzymes (normally in the Bacteria and the body's own digestive enzymes (normally in the

intestine) spread through the body, contributing to its intestine) spread through the body, contributing to its decomposition. decomposition.

► Without the normal defenses of a living animal, blowflies and Without the normal defenses of a living animal, blowflies and house flies are able to lay eggs around wounds and natural body house flies are able to lay eggs around wounds and natural body openings (mouth, nose, eyes, anus, genitalia) and any wounds. openings (mouth, nose, eyes, anus, genitalia) and any wounds.

► These eggs hatch and move into the body, often within 24 hours. These eggs hatch and move into the body, often within 24 hours. The life cycle of a fly from egg to maggot to fly takes from two to The life cycle of a fly from egg to maggot to fly takes from two to three weeks. It can take considerably longer at low three weeks. It can take considerably longer at low temperatures. temperatures.

Flesh flies - Family Flesh flies - Family SarcophagidaeSarcophagidae

Blowflies - Family Blowflies - Family CalliphoridaeCalliphoridae

Blowfly LarvaeBlowfly Larvae

Stage 2: Putrefaction - 4 to 10 Stage 2: Putrefaction - 4 to 10 days after deathdays after death

► Putrefaction begins; gases produced by anaerobic Putrefaction begins; gases produced by anaerobic bacteria; considerable bloating; seepage of fluids; bacteria; considerable bloating; seepage of fluids;

► Larval activity speeds up decomposition - the smells Larval activity speeds up decomposition - the smells and body fluids that begin to emanate from the body and body fluids that begin to emanate from the body attract more blowflies, flesh flies, beetles and mites. attract more blowflies, flesh flies, beetles and mites.

► The later-arriving flies and beetles are predators, The later-arriving flies and beetles are predators, feeding on maggots as well as the decaying flesh. feeding on maggots as well as the decaying flesh. They are joined by parasitoid wasps that lay their They are joined by parasitoid wasps that lay their eggs inside maggots and later, inside pupae. eggs inside maggots and later, inside pupae.

Stage 3: Black putrefaction - 10 Stage 3: Black putrefaction - 10 to 20 days after deathto 20 days after death

► Abdominal wall is broken and carcass deflates Abdominal wall is broken and carcass deflates ► By this stage, several generations of maggots are present on By this stage, several generations of maggots are present on

the body and some have become fully grown. the body and some have become fully grown. They migrate from the body and bury themselves in the soil They migrate from the body and bury themselves in the soil

where they become pupae. where they become pupae. ► Predatory maggots are much more abundant at this stage, Predatory maggots are much more abundant at this stage,

and the pioneer flies cease to be attracted to the corpse. and the pioneer flies cease to be attracted to the corpse. ► Predatory beetles lay their eggs in the corpse and their larvae Predatory beetles lay their eggs in the corpse and their larvae

then hatch out and feed on the decaying flesh. then hatch out and feed on the decaying flesh. ► Parasitoid wasps are much more common, laying their eggs Parasitoid wasps are much more common, laying their eggs

inside maggots and pupae. inside maggots and pupae.

Hister Beetles Prey on Blowfly Hister Beetles Prey on Blowfly LarvaeLarvae

Stage 4: Butyric fermentation - Stage 4: Butyric fermentation - 20 to 50 days after death20 to 50 days after death

► All the remaining flesh is removed over this period and the All the remaining flesh is removed over this period and the body dries out. It has a cheesy smell, caused by butyric acid, body dries out. It has a cheesy smell, caused by butyric acid, and this smell attracts a new suite of corpse organisms. and this smell attracts a new suite of corpse organisms.

► The reduction in soft food makes the body less palatable to The reduction in soft food makes the body less palatable to the mouth-hooks of maggots, and more suitable for the the mouth-hooks of maggots, and more suitable for the chewing mouthparts of beetles. Beetles feed on the skin and chewing mouthparts of beetles. Beetles feed on the skin and ligaments. Many of these beetles are larvae. They hatch from ligaments. Many of these beetles are larvae. They hatch from eggs, laid by adults, which fed on the body in earlier stages of eggs, laid by adults, which fed on the body in earlier stages of decay. decay.

► The cheese fly consumes any remaining moist flesh at this The cheese fly consumes any remaining moist flesh at this stage, even though it is uncommon earlier in decay. stage, even though it is uncommon earlier in decay.

Stage 5: Dry decay - 50-365 Stage 5: Dry decay - 50-365 days after death days after death

► The body is now dry and decays very slowly. Eventually The body is now dry and decays very slowly. Eventually all the hair disappears leaving the bones only. all the hair disappears leaving the bones only.

► Animals which can feed on hair include moths, and Animals which can feed on hair include moths, and micro-organisms like bacteria. Mites, in turn, feed on micro-organisms like bacteria. Mites, in turn, feed on these micro-organisms. these micro-organisms.

► They remain on the body as long as traces of hair They remain on the body as long as traces of hair remain, which depends on the amount of hair that remain, which depends on the amount of hair that covers the particular species. Humans and pigs have covers the particular species. Humans and pigs have relatively little hair and this stage is short for these relatively little hair and this stage is short for these species. species.