1. Determining the Time of Death (TOD)

2. Maggots and Murder

3. Forensic Entomology
Using the developmental stages of insects to determine TOD
Larvae
Pupae
Eggs
Adult
Adult

4. Forensic Entomology
The study of insects in relation to a criminal investigation.
Insects arrive at a decomposing body in a particular order and then complete their life cycle based on the surrounding temperature.
By collecting and studying the types of insects found on a body, a forensic entomologist can predict the time of death.
“When one biological clock stops, others begin.”
--Neal Haskell, reknown forensic entomologist

6. Determining the Time of Death (TOD) Using Forensic Entomology

7. Stages of Decomposition
Initial Decay-Although body shortly after death appears fresh from outside-bacteria in body’s intestine before death begin to digest intestine itself.
Autolysis-bacteria exit intestine and digest internal organs. The body's own digestive enzymes spread throughout body
Enzymes inside cells-released when cell dies-break down cell and connections with other cells
Flies are immediately attracted to dead bodies Without normal defense of living animal- blowflies and house flies lay eggs around wounds and body openings
Eggs hatch and move into body within 24 hours. Life cycle of a fly from egg to maggot to fly-2-3e weeks

8. Stages of Decomposition
2. Putrefaction-4-10 days after death
Putrefaction-destruction of soft tissues by of micro-organisms-results in catabolism of tissue into gases and liquids
First visible sign-formation of sulfhaemoglobin in settled blood.
Releasing fluids into body cavities-anaerobic respiration - produce hydrogen sulphide, methane, cadaverine, putrescine, butyric and propionic fatty acids
Distention of gut-Gas build up from multiplying bacteria-internal pressure-inflates body and forces fluids from cells and blood vessels into body cavity
Rate of decay increases-blowflies, flesh flies, beetles and mites
Late-arriving insects-predators-feed on maggots and flesh -Maggot masses

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

13. Stages of Decomposition
3. Black Putrefaction days after death
Bloated body collapses-creamy flesh-exposed parts are black in color and very strong smell of decay.
Body fluids drain from body and seep into soil
Insects consume most of the flesh and body temperature increases with activity.
Bacterial decay important-bacteria consume body if insects are excluded
Several generations of maggots-migrate from body and bury in soil to pupate
Predatory maggots are much more abundant
Pioneer flies cease to be attracted to corpse.
Predatory beetles lay their eggs in the corpse and their larvae then hatch out and feed on flesh

15. One week old pig-larva develop & migrate from body to pupate

19. Butyric Fermentation 20-50 days after death
Dessication of corpse-remaining flesh is removed and butyric acid released
The surface of body in contact with ground becomes covered with mold as body ferments.
Beetle larva and adults feed on skin and ligaments.
Predators and parasitic wasps and beetles

22. Dry Decay 50-365 days after death
Body is dry and decays slowly-Eventually leaving only skeleton
Diagenesis-process that changes skeleton’s proportions of organic (collagen) and inorganic components (hydroxyapatite, calcium, magnesium)

26. PMI--Postmortem Interval
PMI-amount of time b/w TOD and body’s discovery
Estimation of PMI- set minimal and maximal PMI
Minimal PMI -determined by estimating age of developing immature insects collected when corpse is discovered
Maximum PMI-determined from species of insects present and weather conditions needed for the activity of these species

27. Temperature
Ambient heat plays a role during egg and early larval development but 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 F.

28. Forensic Entomology
Using developmental stages of insects to determine TOD
Larvae
Pupae
Eggs
Adult
Adult

29. Forensic Entomology
The study of insects in relation to a criminal investigation
Insects arrive at decomposing body in a sequence and complete their life cycle based on surrounding temperature
Forensic entomologist can predict the time of death

31. Metamorphosis
Complete metamorphosis (holometabolous) -development from egg to larva to pupa to adult
The white crust in the picture are the fly eggs.

32. Larva
Larva hatch from the eggs and increase in size by growth steps called instars.
Larva migrate from corpse and develop into an inactive pupal stage
During this time, the adult insect develops internally.
Two larval instars.

33. The Blowfly Acts as both necrophages and as predator
One of the most common species on dead bodies
Often arrive within 10 minutes
Feed on blood and lays eggs in body cavities
If food source is exhausted- will prey on other species in same genus (Chrysomya)

36. Maggots (fly larvae) are remarkable eating machines
Posterior spiracles
Spiracles are used for breathing-posterior spiracles-means that maggots can breath & feed 24 hrs a day

37. First instar
Third Instar
Second instar

39. Pupal Stages of House Fly

43. Types of Insect Collections
Collection are done in three ways:
Aerial
Hand
Live Sampling

44. Aerial Collection Use a net in figure 8 motion over cadaver
Collect flies and put them in ethyl acetate
After a few seconds-put flies into 75% ethyl alcohol-label date, time, case #, location, sample type and collector.

45. Live Sampling “Maggot Motels”
Collect 10 to 15 live maggots of varying sizes into a rearing chamber
Allow to develop into pupae and then into adults.

46. Hand Collection Collect maggots with forceps
Put in boiling water to stretch them out and fix them
Put maggots into ethanol with a label containing date, time, case #, location and collector

52. First instar
Third Instar
Second instar

53. Maggots can consume 60 per cent of a corpse in less than a week
Maggots can consume 60 per cent of a corpse in less than a week. Video footage: R. Major Windows Media (77kb) Quicktime (275kb)

56. Burying Beetles

57. Hister Beetle

59. Forensic Flies