An Overview of Forensic

Taphonomy

David O. Carter, PhD

Assistant Professor of Forensic Science

Department of Entomology

University of Nebraska-Lincoln, USA

What is forensic

taphonomy?

taphos = grave, burial.

-nomy = system of processes, rules, knowledge.

A response to witness statements.

Use of taphonomy:Identify the deceased

Determine the cause and manner of death

Estimate postmortem interval

Locate clandestine graves

Pathology

Anthropology

Archaeology

Entomology

Microbiology

Geoscience

Botany

Palynology

Mycology

Ornithology

Meteorology

Molecular Biology

Taphonomy Timeline

Empirical Ecology

Empirical Taphonomy

Experimental Taphonomy

Forensic Taphonomy

PREHISTORY PRESENT

Notable early forensic taphonomists

Alexandre Lacassange—France

Étienne Rollet—France

Edmond Locard—France

Jean-Pierre Mégnin—France

Johann Casper—Germany

3rd edition published

1861

Haglund and Sorg 1997

Identify the Deceased

Friction Ridges

Friction ridge pattern = ridges + furrows

Glands release sweat through the pores

Begin to form between 10th & 12th week of pregnancy

Fully formed by 24th week

Are permanent and unique

Can be well preserved when desiccated

Fingerprint detail

Level 1Ridge Flow: direction that ridges flow

Level 2Ridge Events: breaks, splits and endings within the ridge

pattern

Level 3Ridge Dimensions: size attributes and spatial location of

ridges and pores.

Level 1: Ridge Flow

Ridge Flow is determined by the configuration and direction of ridges.

This defines the “pattern type”.

Three patterns:Arch

Loop

Whorl

Level 2: Ridge Events

1) Ridge ending

2) Bifurcation

3) Dot

4) Short ridge

5) Enclosure

enclosure

Ridge

ending

dot

bifurcation

Short ridge

Level 3: Ridge Dimensions

Each ridge has a unique

Width, shape, edge contour

Pores vary in

Number

Shape

Placement

Fingerprint Comparisons

Compare known to unknown

Compare to fingerprints stored in AFIS and IAFIS

AFIS

Automated Fingerprint Identification System

Can differ from agency to agency

IAFIS

Integrated AFIS

US National System

Forensic Biochemistry

Genetic analysisAutosomal DNA

Mitochondrial DNA

Y-STR

SerologyABO typing

Rhesus factor

Saliva

Semen

Cause and Manner of Death

Cause of deathEvent or disease process that led to death (e.g. gunshot, blunt

force trauma)

Manner of deathNatural

Accidental

Suicide

Homicide

Undetermined

When is an autopsy done?(in Nebraska)

1. When Manner is:

Accidental

Suicide

Homicide

Undetermined

2. When the doctor wants it.

Gunshot wounds

Should be used for exclusion.

Forensic Chemistry

Toxicology

Blood alcohol

Vitreous humor

Cardiac blood

Femoral blood

Organs

Controlled Substances

Powders

Pills

Liquids

Plants

Spores

Postmortem Interval

Postmortem Interval (PMI)The time elapsed since death.

One 100% accurate estimate:

Maximum PMI equals the time elapsed since the

person was last seen alive and found dead.

A collection of direct and indirect methods aim to

narrow that estimate.

Postmortem IntervalWhat is used to estimate PMI?

Rate methods: based on process that begins or

ends at death; e.g. rigor mortis, maggot

development.

Accuracy tends to decrease as PMI increases.

Concurrence methods: sequencing events that

occurred at known times around death; e.g. phone

records, emails, receipts, stopped watch.

Why narrow the PMI estimate?

Can help identify people

Can help accept or reject alibi

Can help reconstruct series of events

Direct Estimates of PMI

Algor mortis

Believed that body cooled 1.5 degrees F per hour after

death.

Thermometer inserted 3-4” into the rectum.

Must know:

Temperature at death

Duration of temperature plateau

Algor mortis is not acceptable for estimating PMI

Livor mortis

Livor mortis usually observed between 20 and 120

minutes postmortem.

Believed that livor mortis becomes fixed at 10-12 hours

postmortem.

Livor mortis is not acceptable for estimating PMI

Rigor mortis

Estimates:

Becomes noticeable 3-4 hours postmortem

Full rigor by 12 hours postmortem

Lapsed by 36 hours postmortem

Rigor mortis is not acceptable for estimating PMI

Vitreous humor

Measure of the concentration of potassium (K) over time

31% accurate, most often overestimates PMI

Most accurate within 24 hours postmortem

Vitreous humor is not acceptable for estimates of PMI

Forensic Anthropology

Indirect Estimates of PMI

Degree Days

Step 1:

maximum temperature + minimum temperature

2

Step 2:

subtract ‘base temperature’

base temperature = the lowest temperature at which that organism will grow.

Accumulated Degree

Days

Sum each degree day

Some taphonomists use Accumulated Degree Hours in an

attempt to increase precision.

Forensic Entomology

Using the development of insects to estimate PMI

Using the succession of insects to estimate PMI

Key to understanding this use is through understanding

the Degree Day

Needed for Forensic

EntomologySpecies of blow fly (Diptera: Calliphoridae)

Age of blow fly

Temperature at crime scene

Growth rate of blow fly species

Egg 1st stage 2nd stage 3rd stage pupa

ADDs 374 418 572 1012 3014

Hours at 22

°C

17 19 26 46 137

Grassberger and Reiter (2001) Forensic Sci Int 120:32-36

Gravesoils

Probably the best way to estimate PMI once maggots

have migrated.

Based on concentration of chemicals in gravesoil and

accumulated degree days.

At present, gravesoil PMI estimates use base temperature

of 0 °C.

Not certain if this is correct.

nutrient concentration

0

100

200

300

400

500

600

0 1000 2000 3000 4000 5000

pp

m n

utr

ien

t g-1

so

il kg-1

ca

da

ve

r

Accumulated degree days

ammonium

potassium

chloride

calcium

Vass et al. (1992) J Forensic Sci 37:1236-

1253

Volatile Fatty Acids

0

2

4

6

8

10

12

14

16

0 200 400 600 800 1000 1200

mm

ol V

FA

g-1

so

il k

g-1

cad

av

er

Accumulated degree days

propionic

n-butyric

iso-valeric

1285 ADDs = no more

VFAs

Vass et al. (1992) J Forensic Sci 37:1236-

1253

Vass’s rule of thumb for PMI

For pre-skeletonized bodies

1285 degree days = end of volatile fatty acid release

1285 ÷ average temperature (°C) on day of discovery =

approximate maximum PMI

Consider average temperature of 22 °C:

1285/22 = 58.4

58.4 days = maximum PMI

Newest PMI equations

• Aboveground Decomposition

1285 x (decomposition/100)0.0103 x temperature x humidity

• Belowground Decomposition

1285 x (decomposition/100) x 4.6 x adipocere0.0103 x temperature x soil moisture

ninhydrin-reactive nitrogen

Ninhydrin-reactive nitrogen is

protein

peptide

amino acids

ammonium

Gravesoil NRN can remain elevated for 1 year.

Gravesoil pH can be significantly lower for 1 year.

• An increase in NRN occurs after 320 ADDs regardless of death in winter

or summer

Locating Clandestine Graves

Dupras et al. (2005)

Hunter et al. 1996

Dupras et al. (2005)

Dupras et al. (2005)

Similarities between Crime Scene

Investigation and Archaeology

1st responder is responsible for success

One chance to recover information: destructive process

Documentation is critical

Reconstruction based on physical evidence

Enhancement used to locate objects

Ground Penetrating Radar, resistivity, thermal imaging, etc.

Reports produced

References

Dupras TL et al. (2005) Forensic Recovery of Human Remains:

Archaeological Approaches. CRC Press.

Gunn A (2009) Essential Forensic Biology. 2nd Edition. Wiley-

Blackwell.

Houck MM, Siegel JA (2010) Fundamentals of Forensic

Science. 2nd Edition. Academic Press.

Hunter J et al. (1997) Studies in Crime: An Introduction to

Forensic Archaeology. Batsford.

James S, Nordby JJ (2009) Forensic Science: An Introduction to

Scientific and Investigative Techniques. 3rd Edition. CRC Press.

David O. Carter, PhD

Assistant Professor of Forensic Science

Department of Entomology

University of Nebraska-Lincoln, USA

dcarter2@unl.edu