Decomposition, Forensic Entomology, and Forensic

Anthropology

http://people.stu.ca/~mclaugh/skeleton8a.GIF

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

Conditions That Affect Decomposition

• Air temperature/ weather conditions– Colder = slower decomposition; warmer =

faster decomposition

• Clothed vs. Naked body– Clothed slower, naked faster decomp.

• Underwater—slower decomposition

• Severe wounds = faster decomp– Insects get into body faster

1.) Initial Decay

1.) Initial Decay: 0 to 3 days after death – Autolysis

• Body digested from inside out—usually starts in pancreas

– Body relatively fresh– Bugs start invading “openings” in body

• Mouth/ Eyes• Vagina/ Anus• Open wounds

2.) Putrefaction

2.) Putrefaction: 4-10 days after death– Bacteria release gases, causes bloating

• hydrogen sulfide, methane, cadaverine, and putrescine

– Cells break down, release fluids—more bugs• More flies, beetles, and mites

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

4.) Butyric Fermentation

4.) Butyric Fermentation: 20-50 days after death– Body smells like cheese– Body starts to dry out—no more flies

• Specialized mites and beetles

– Mold grows where body touches ground

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

Time of Death

• Rigor Mortis: Stiffening of body after death– Starts immediately

• Manifested 1-6 hours• Maximum 6-24 hours• Disappears 12-36 hours

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!

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

Forensic Entomology

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

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

Succession of species

Larvae

Adult

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.

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 hatch—1st 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

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)

Forensic Entomology:Flies

SarcophagidaeSarcophagidae - flesh flies•Adults lay larvae on decaying flesh•Some of the first insect to reach a corpse

CalliphoridaeCalliphoridae – 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

Forensic Entomology:Flies

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

Forensic EntomologyCarrion beetles

SilphidaeSilphidae – Carrion beetles

•Buries small carcasses•Adults feed on maggots and carrion

Forensic Entomology:Beetles

StaphylinidaeStaphylinidae – rove beetles•Arrive a few hours after a death •Are active throughout decomposition process

DermestidsDermestids – Carpet beetle•Larvae and adults feed on dry skin and hairs

Histeridae Histeridae – Hister beetles•Found in bloated, decay, and early drying stages•Both larvae and adults feed on maggots and puparia

Temperature–Dependent 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"

Effect of temperature on insect development

Forensic EntomologyCase Studies

Cannabis seized in New ZealandThe 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

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

Case studyA 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.

Why Study Bones?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: From: "Human Osteology - A Laboratory and Field Manual" 3rd Edition, 1987"Human Osteology - A Laboratory and Field Manual" 3rd Edition, 1987

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

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

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 > 90 > 90°°

females have a broad pelvic inlet

1. 1.

1.

2. 2.

2.

3.3.

3.

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. 1.

2. 2.3.

1.

2.

3.

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)

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

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.

White, Asian, African

From: Beyers, S.N. (2005). Introduction to Forensic Anthropology

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

Nasal Silling and Guttering

From: Beyers, S.N. (2005). Introduction to Forensic Anthropology

General Shapes of the Eye Orbits

From: Beyers, S.N. (2005). Introduction to Forensic Anthropology

Determination of Race:

Caucasian

http://upload.wikimedia.org/wikipedia/en/c/cc/Skullcauc.gif

Trait

Nasal Index: <.48

Nasal Spine: Prominent spine

Nasal Silling / Guttering:

Sharp ridge (silling)

Prognathism: Straight

Shape of Orbital Openings:

Rounded, somewhat square

Nasal spine:Prominent

Progathism: straight

Orbital openings:round

Determination of Race:Asian (Asian decent and Native American

decent)

http://upload.wikimedia.org/wikipedia/en/b/b3/Skullmong.gif

Trait

Nasal Index .48-.53

Nasal SpineSomewhat

prominent spine

Nasal Silling/ Guttering

Rounded ridge

Prognathism Variable

Shape of Orbital

Openings

Rounded, somewhat circular

Determination of Race:African: (everyone of African decent and West Indian decent)

http://upload.wikimedia.org/wikipedia/en/5/5e/Skullneg.gif

Trait

Nasal Index >.53

Nasal Spine Very small spine

Nasal Silling/ Guttering

No ridge (guttering)

Prognathism Prognathic

Shape of Orbital Openings

Rectangular or square

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)

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

Epiphyseal Fusion:

A General Guide

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 1. Figure 2.

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

2. Age Determination: Use of Teeth

http://images.main.uab.edu/healthsys/ei_0017.gifhttp://www.forensicdentistryonline.org/Forensic_pages_1/images/Lakars_5yo.jpg

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 (5’6”) ± 4.57 cm

See your lab handout for more tables

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/index.html

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/index.ht

ml• 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?page

=how&title=Forensic%20Anthropology• Great, interactive site:

– http://whyfiles.org/192forensic_anthro/

Lab: the bones we’re interested

in

Tibia

Pelvis

Humerus

Skull

Femur

Sex Determination - Pelvis

• Sub-Pubic Angle

• Pubis Body Width

• Greater Sciatic Notch

• Pelvic Cavity Shape

http://mywebpages.comcast.net/wnor/pelvis.htm

Sex Determination - Skull

Trait Female Male

Upper Edge of Eye Orbit Sharp Blunt

Shape of Eye Orbit Round Square

Zygomatic ProcessNot 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

Sex Determination - Tibia

Lateral Condyle

Medial Condyle

“Ankle Bone”http://www.anatomyatlases.org/atlasofanatomy/plate06/images/6-5_static.jpg

Proximal End

Distal End

If You’re In Doubt…

• If you don’t 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