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Title: Decomposition, Forensic Entomology, and Forensic Anthropology


1
Decomposition, Forensic Entomology, and Forensic
Anthropology
http//people.stu.ca/mclaugh/skeleton8a.GIF
2
Stages of Decomposition
  • 1.) Initial Decay 0-3 Days
  • 2.) Putrefaction 3-10 Days
  • 3.) Black Putrefaction 10-20 Days
  • 4.) Butyric Putrefaction 20-50 Days
  • 5.) Dry Decay 50-365 Days

3
Conditions That Affect Decomposition
  • Air temperature/ weather conditions
  • Colder slower decomposition warmer faster
    decomposition
  • Clothed vs. Naked body
  • Clothed slower, naked faster decomp.
  • Underwaterslower decomposition
  • Severe wounds faster decomp
  • Insects get into body faster

4
1.) Initial Decay
  • 1.) Initial Decay 0 to 3 days after death
  • Autolysis
  • Body digested from inside outusually starts in
    pancreas
  • Body relatively fresh
  • Bugs start invading openings in body
  • Mouth/ Eyes
  • Vagina/ Anus
  • Open wounds

5
2.) Putrefaction
  • 2.) Putrefaction 4-10 days after death
  • Bacteria release gases, causes bloating
  • hydrogen sulfide, methane, cadaverine, and
    putrescine
  • Cells break down, release fluidsmore bugs
  • More flies, beetles, and mites

6
3.) Black Putrefaction
  • 3.) Black Putrefaction 10-20 days after death
  • Bloating collapses, tissues get creamy like
    cottage cheese
  • Exposed tissue turns black
  • Fluids spill into soil, bugs really start eating
    body

7
4.) Butyric Fermentation
  • 4.) Butyric Fermentation 20-50 days after death
  • Body smells like cheese
  • Body starts to dry outno more flies
  • Specialized mites and beetles
  • Mold grows where body touches ground

8
5.) Dry Decay
  • 5.) Dry Decay 50-365 days after death
  • Bones and hair remain with some dried tissue
  • Tinead moths and bacteria eat hair
  • Bones can remain almost indefinitely
  • Animals will eat and carry away bones

9
Time of Death
  • Rigor Mortis Stiffening of body after death
  • Starts immediately
  • Manifested 1-6 hours
  • Maximum 6-24 hours
  • Disappears 12-36 hours

10
Time of Death
  • Livor Mortis Settling of blood in body
  • Gravity settles blood to lowest point on body, if
    on back, buttocks and shoulder blades
  • Starts Immediately
  • Manifested 2-4 hours
  • Blood dried and settled 8-12 hours
  • If a body is moved and turned over after 12
    hours, you will know the body has been moved
    post-mortem!

11
Time of Death
  • Algor Mortis Temperature of decomposing body
  • Starts immediately and stops whenever the body
    temp reaches the ambient temp
  • Remember factors that affect decomposition also
    affect algor mortis!
  • Forensic scientists use the equation
  • 98.4º F measured rectal temp time (hours)
  • 1.5 since death

12
Forensic Entomology
13
Forensic EntomologyHow insects are used
  • PMI Post Mortem Interval using degree day
    models and life history information
  • The type of insect
  • Stage of development
  • Location of murder
  • Species Present
  • Finding an insect not generally present at body
    site suggests the body has been moved.
  • Presence of drugs
  • Can be sequestered in insects found on bodies

14
Faunal Succession
  • Sequence, pattern, and duration of insect
    activity
  • Insects invade bodies in waves
  • Estimation of time since death requires
  • Ability to identify each species in all stages of
    their life cycles
  • Knowledge of the time occupied by each life stage
    under various conditions
  • Great accuracy initially, less accurate with
    increasing time
  • Primarily study beetle and flies

15
Succession of species
Adult
Larvae
16
Faunal succession
  • Linked to the natural changes which take place in
    a body after death
  • After the onset of autolysis and putrefaction,
    necrophagous insects appear, depending on time of
    year and situation of cadaver
  • Necrophagous insect
  • ecological category for anything feeding on
    carrion
  • Necrophagous insect activity accelerates
    putrefaction and the disintegration of the
    corpse.
  • Gases excreted from the body (methane, ammonia,
    carbon dioxide, nitrogen) attract the insects,
    not necessarily blood.

17
Faunal succession
  • 1st arrival usually blowflies (within minutes)
  • Females lay 200-300 eggs each (clumps of whitish
    beadlike dots, usually in orifices)
  • 1-2 days later, eggs hatch1st instar maggots
  • Typically there are about 3 instars of maggothood
  • Pupation after about one to two weeks as a
    maggot, the outer chitin of the maggot body
    hardens, darkens, forms a shell inside of which
    the maggot metamorphizes into the beautiful adult
    fly (about a 1 week process).
  • All together, blowflies emerge about 2 weeks
    after eggs are laid

18
Faunal succession Beetles
  • Beetles may appear during massive maggot activity
  • Some beetles eat maggots
  • The height of some beetle activity is after the
    first generation of flies have come and gone
  • Necrophagous beetles
  • Carrion beetles (Silphidae)
  • Rove beetles (Staphylinidae)
  • Scarab beetles (Scarabaeidae)
  • Leiodid beetles (Leiodidae)

19
Forensic EntomologyFlies
  • Sarcophagidae - flesh flies
  • Adults lay larvae on decaying flesh
  • Some of the first insect to reach a corpse
  • Calliphoridae blowflies
  • Different species have different habits light
    vs. dark, urban vs. rural
  • All have larvae that feed on corpses
  • Also one of the first to arrive

20
Forensic EntomologyFlies
  • Strateomyidae soldier flies
  • Larvae feed on human excrement and remains
  • Are found late in decomposition process
  • Phoridae humpbacked flies
  • Larvae feed on decaying bodies
  • Some species can burrow to a depth of 50cm over 4
    days
  • Important in buried bodies

21
Forensic EntomologyCarrion beetles
  • Silphidae Carrion beetles
  • Buries small carcasses
  • Adults feed on maggots and carrion

22
Forensic EntomologyBeetles
  • Staphylinidae rove beetles
  • Arrive a few hours after a death
  • Are active throughout decomposition process
  • Dermestids Carpet beetle
  • Larvae and adults feed on dry skin and hairs
  • Histeridae Hister beetles
  • Found in bloated, decay, and early drying stages
  • Both larvae and adults feed on maggots and puparia

23
TemperatureDependent Development
  • Insects are cold blooded.
  • Rate of development is more or less dependent on
    ambient temperature
  • For each species there is a threshold temperature
    below which no development occurs
  • As temperature rises above this threshold, a
    certain amount of time is required for the insect
    to pass through each life stage.
  • Because this heat is accumulated as "thermal
    units," it can be calibrated and described as
    "degree-days" or "degree-hours"

24
Effect of temperature on insect development
25
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26
Forensic EntomologyCase Studies
Cannabis seized in New Zealand
The Facts
  • 60 insect specimens were recovered from two
    separate cannabis seizures in New Zealand
  • Only one, the rice weevil, was native to New
    Zealand
  • 8 other species native only to Asia

The methods
  • Plotted distributions of the 8 Asian Species
  • Studied the overlap of these distributions

27
Forensic EntomologyCase Studies
Cannabis seized in New Zealand -continued
The conclusions
  • Cannabis originated in the Tenasserim region
    between the Andaman Sea to the west and Thailand
    in the east
  • From the known habitats of insects it was
    concluded that the cannabis was harvested near a
    stream or a lake with fig trees and termite nests
    nearby

28
Case study
A window next to the victim was open when the
body was found, thus giving the impression that
the murderer had forced entry into the room the
night before. However, the air conditioned room
was cool even though it was very hot outdoors. In
reality, the killer was known to the victim, had
a key, and had returned to "set the stage" by
opening the window just prior to feigning
discovery of the corpse. The insects thus had
insufficient time to colonize the body because
the window had been closed prior to the return of
the killer. When confronted by this biological
reality as pointed out by entomology, the killer
confessed.
29
Why Study Bones?
  • They constitute the evidence for the study of
    fossil man.
  • They are the basis of racial classification in
    prehistory.
  • They are the means of biological comparison of
    prehistoric peoples with the present living
    descendents.
  • They bear witness to burial patterns and thus
    give evidence for the culture and world view of
    the people studied.
  • They form the major source of information on
    ancient diseases and often give clues as to the
    causes of death.
  • Their identification often helps solve forensic
    cases.

From "Human Osteology - A Laboratory and Field
Manual" 3rd Edition, 1987
30
A Caveat
  • Informative features about the age, sex, race and
    stature of individuals based on bones is based on
    biological differences between sexes and races
    (males are generally taller and more robust) as
    well as differences due to ancestry (certain
    skeletal features of the skull)
  • However, it is imprecise because so much human
    variation exists and because racial differences
    tend to homogenize as populations interbreed
  • Still differences do exist and the more features
    you survey, the more precise your conclusions
    will be

31
What Can We Learn?
  • Determination of Sex
  • Pelvis
  • Skull
  • Determination of Race
  • Skull
  • Approximate Age
  • Growth of long bones
  • Approximate Stature
  • Length of long bones
  • Postmortem or antimortem injuries
  • Postmortem interval (time of death)

http//en.wikipedia.org/wiki/Forensic_anthropology
32
  • 1. Determination of Sex
  • Pelvis is the best bones (differences due to
    adaptations to childbirth)
  • females have wider subpubic angle
  • females have a sciatic notch gt 90
  • females have a broad pelvic inlet

1.
2.
3.
2.
2.
3.
3.
1.
1.
33
  • 1. Determination of Sex
  • Pelvis best (another view)
  • females have wider subpubic angle
  • females have a broad, shovel-like ilium
  • females have a flexible pubic symphysis

1.
2.
3.
2.
3.
2.
1.
1.
34
1. Determination of Sex Cranium
  • Crests and ridges more pronounced in males (A, B,
    C)
  • Chin significantly more square in males (E)
  • Mastoid process wide and robust in males
  • Forehead slopes more in males (F)

35
1. Determination of Sex
  • Normally, the long bones alone are not used alone
    to estimate gender. However, if these bones are
    the only ones present, there are characteristics
    that can be used for sex determination.
  • E.g. maximum length of humerus in females is
    305.9 mm, while it is 339.0 mm in males

36
Determination of Race
  • It can be extremely difficult to determine the
    true race of a skeleton for several reasons
  • First, forensic anthropologists generally use a
    three-race model to categorize skeletal traits
    Caucasian (European), Asian (Asian/Amerindian),
    and African (African and West Indian).
  • Although there are certainly some common physical
    characteristics among these groups, not all
    individuals have skeletal traits that are
    completely consistent with their geographic
    origin.
  • Second, people of mixed racial ancestry are
    common.
  • Often times, a skeleton exhibits characteristics
    of more than one racial group and does not fit
    neatly into the three-race model.
  • Also, the vast majority of the skeletal
    indicators used to determine race are non-metric
    traits which can be highly subjective.
  • Despite these drawbacks, race determination is
    viewed as a critical part of the overall
    identification of an individual's remains.

37
White, Asian, African
From Beyers, S.N. (2005). Introduction to
Forensic Anthropology
38
Features of the Skull Used in Race Determination
  • Nasal index The ratio of the width to the height
    of the nose, multiplied by 100
  • Nasal Spine
  • Feel the base of the nasal cavity, on either side
    of the nasal spine do you feel sharp ridges
    (nasal silling), rounded ridges, or no ridges at
    all (nasal guttering)?
  • Prognathism extended lower jaw
  • Shape of eye orbits (round or squareish

Nasal spine
39
Nasal Silling and Guttering
From Beyers, S.N. (2005). Introduction to
Forensic Anthropology
40
General Shapes of the Eye Orbits
From Beyers, S.N. (2005). Introduction to
Forensic Anthropology
41
Determination of RaceCaucasian
Trait
Nasal Index lt.48
Nasal Spine Prominent spine
Nasal Silling / Guttering Sharp ridge (silling)
Prognathism Straight
Shape of Orbital Openings Rounded, somewhat square
http//upload.wikimedia.org/wikipedia/en/c/cc/Skul
lcauc.gif
42
Determination of RaceAsian (Asian decent and
Native American decent)
Trait
Nasal Index .48-.53
Nasal Spine Somewhat prominent spine
Nasal Silling/ Guttering Rounded ridge
Prognathism Variable
Shape of Orbital Openings Rounded, somewhat circular
http//upload.wikimedia.org/wikipedia/en/b/b3/Skul
lmong.gif
43
Determination of RaceAfrican (everyone of
African decent and West Indian decent)
Trait
Nasal Index gt.53
Nasal Spine Very small spine
Nasal Silling/ Guttering No ridge (guttering)
Prognathism Prognathic
Shape of Orbital Openings Rectangular or square
http//upload.wikimedia.org/wikipedia/en/5/5e/Skul
lneg.gif
44
Determination of Age
  • The long bones are those that grow primarily by
    elongation at an epiphysis at one end of the
    growing bone. The long bones include the femurs,
    tibias, and fibulas of the legs, the humeri,
    radii, and ulnas of the arms, and the phalanges
    of the fingers and toes.
  • As a child grows the epiphyses become calcified
    (turn to hard bone)

45
2. Determination of Age from Bones
  • Ages 0-5 teeth are best forensic odontology
  • Baby teeth are lost and adult teeth erupt in
    predictable patterns
  • Ages 6-25 epiphyseal fusion fusion of bone
    ends to bone shaft
  • epiphyseal fusion varies with sex and is
    typically complete by age 25
  • Ages 25-40 very hard
  • Ages 40 basically wear and tear on bones
  • periodontal disease, arthritis, breakdown of
    pelvis, etc.
  • Can also use ossification of bones such as those
    found in the cranium

46
Epiphyseal Fusion A General Guide
47
Epiphyseal Fusion
  • The figures below are of the Epiphyses of the
    femur or thigh bone (the ball end of the joint,
    joined by a layer of cartilage).
  • The lines in the illustrated Image 1 show the
    lines or layers of cartilage between the bone and
    the epiphyses. The lines are very clear on the
    bone when a person, either male or female is not
    out of puberty.
  • In Image 2, you see no visible lines. This person
    is out of puberty. The epiphyses have fully
    joined when a person reaches adulthood, closing
    off the ability to grow taller or in the case of
    the arms, to grow longer.

Figure 2.
Figure 1.
48
2. Determination of Age from Bone Signs of
wearing and antemortem injury
Occupational stress wears bones at joints
Surgeries or healed wounds aid in identification
http//library.med.utah.edu/kw/osteo/forensics/pos
_id/boneid_th.html
49
2. Age Determination Use of Teeth
http//images.main.uab.edu/healthsys/ei_0017.gif
http//www.forensicdentistryonline.org/Forensic_pa
ges_1/images/Lakars_5yo.jpg
50
3. Determination of Stature
  • Long bone length (femur, tibia, humerus) is
    proportional to height
  • There are tables that forensic anthropologists
    use (but these also depend to some extent on
    race)
  • Since this is inexact, there are confidence
    intervals assigned to each calculation.
  • For example, imagine from a skull and pelvis you
    determined the individual was an adult Caucasian,
    the height would be determine by
  • Humerus length 30.8 cm
  • Height 2.89 (MLH) 78.10 cm
  • 2.89 (30.8) 78.10 cm
  • 167 cm (56) 4.57 cm
  • See your lab handout for more tables

51
4. Other Information We Can Get From Bones
  • Evidence of trauma (here GSW to the head)
  • Evidence of post mortem trauma (here the head of
    the femur was chewed off by a carnivore)

http//library.med.utah.edu/kw/osteo/forensics/ind
ex.html
52
Sources
  • A very good website with photos and information
    on forensic anthropology (including estimating
    age, stature, sex and race)
  • http//library.med.utah.edu/kw/osteo/forensics/ind
    ex.html
  • A good site with a range of resources
  • http//www.forensicanthro.com/
  • Another good primer for determining informtion
    from bones
  • http//www.nifs.com.au/FactFiles/bones/how.asp?pag
    ehowtitleForensic20Anthropology
  • Great, interactive site
  • http//whyfiles.org/192forensic_anthro/

53
Lab the bones were interested in
Skull
Humerus
Pelvis
Femur
Tibia
54
Sex Determination - Pelvis
  • Sub-Pubic Angle
  • Pubis Body Width
  • Greater Sciatic Notch
  • Pelvic Cavity Shape

http//mywebpages.comcast.net/wnor/pelvis.htm
55
Sex Determination - Skull
Trait Female Male
Upper Edge of Eye Orbit Sharp Blunt
Shape of Eye Orbit Round Square
Zygomatic Process Not expressed beyond external auditory meatus Expressed beyond external auditory meatus
Nuchal Crest (Occipital Bone) Smooth Rough and bumpy
External Occipital Protuberance Generally Absent Generally present
Frontal Bone Round, globular Low, slanting
Mandible shape Rounded, V-shaped Square, U-shaped
Ramus of mandible Slanting Straight
56
Sex Determination - Tibia
Medial Condyle
Proximal End
Lateral Condyle
Distal End
Ankle Bone
http//www.anatomyatlases.org/atlasofanatomy/plate
06/images/6-5_static.jpg
57
If Youre In Doubt
  • If you dont know what something is that is
    referenced in the lab
  • Check to see if there is an accompanying picture
    referenced, and turn to it in your lab handout
  • Try Googling either the structure (e.g.
    Wikipedia) or Google image search
  • Ask Artiss
  • Some skeletons have a femur and not a tibia, and
    some have a tibia and not a femur do
    appropriate measurements for whichever you have
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