C Constructing i (and Deconstructing) (and Deconstructing) the - - PowerPoint PPT Presentation

C i Constructing (and Deconstructing) (and Deconstructing) the Postmortem Interval the Postmortem Interval

• H. Gill-King, Ph.D., D-ABFA

Center for Human Identification Center for Human Identification Graduate School of Biomedical Sciences University of North Texas University of North Texas

Estimation of the postmortem interval Estimation of the postmortem interval

remains a persistent challenge, and one of the most important in forensic science. 1 Inclusion and exclusion of suspects 1. Inclusion and exclusion of suspects 2. Civil applications 3 Establishing medicolegal significance 3. Establishing medicolegal significance

General approaches

R h d / D h i Rate methods / Death is a process, not an event not an event Concurrence methods / One event fixed in time correlated with another fixed in time correlated with another

Sources of evidence

1 Corporeal / evidence from the

• 1. Corporeal / evidence from the

body 2 Environmental / contextual

• 2. Environmental / contextual
• 3. Anamnestic / routines

Progression of events Progression of events

• 1. Fresh /early (supravital period)

2 Intermediate (putrefaction decomposition)

• 2. Intermediate (putrefaction, decomposition)
• 3. Extended (aerobic decay, weathering)

All bodies will pass through this progression, l h h h d ll i i h d h although the dwell time in each stage and the

• verall time required may vary considerably.

Intervals Intervals

Short interval (hours to days)

• - irreversible circulatory arrest 

irreversible circulatory arrest 

• - global ischemia 

disruption of membrane pumps

• - disruption of membrane pumps
• - autolysis follows rate of glycolysis and

di d i H corrresponding drop in pH

• - observable changes

Short interval contd.

Rigor mortis – Generalized stiffening of the Rigor mortis Generalized stiffening of the Muscles / onset 2-4 hrs, resolution 24-84 hrs.

Onset and duration will be affected by 1 Agonal state

• 1. Agonal state
• - hyperthermia / hypothermia

b li ( di b

• - metabolic (e.g. diabetes,

electrolyte imbalance, lactic y , acidosis) dehydration

• - dehydration
• 2. Body composition
• 3. Ambient conditions at the scene

Additional problems Additional problems

1 S bjecti it in staging

• 1. Subjectivity in staging
• 2. Lack of contextual information from the

scene Use of rigor mortis as the sole indicator of Use of rigor mortis as the sole indicator of PMI should be avoided.

Algor mortis (cooling)) g ( g))

Dead bodies do not follow Newton’s Exponential Newton s Exponential cooling curve for a variety of reasons. easo s.

Cooling variables

• 1. Strong radiation (e.g. solar or proximity to a heating
• r cooling device)
• 2. Uncertain alternating temperatures (e.g. HVAC system,

i d t ) windows open, etc.) 3 If outdoors extensive climatic changes which do not

• 3. If outdoors, extensive climatic changes which do not

allow for estimates of representative mean values.

• 4. General hypothermia or malignant hyperthermia.

i b li d h b d

• 5. Remains believed to have been transported.

• 6. Body composition

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• 7. Clothing
• 8. Ambient temperature higher than 37C
• 9. Convection and humidity
• 10. Bodies are not uniformly dense. Core to shell and

shell to environment transfer produces a plateau with significant resulting variations during the first 6 hrs.

Livor mortis (hypostasis)

• 1. Visible soon after death.

2 Easily ‘blanched’ for a few hours

• 2. Easily blanched for a few hours.
• 3. Usually ‘fixed’ and cannot be blanched within

8 12 hrs 8-12 hrs.

• 4. Determined by body position for the first few

hours following death hours following death

Quantitative measures of hypostasis, (colorimetric and hemoglobin concentration), correlate with PMI, but are not statistically validated Factors which affect quantification include statistically validated. Factors which affect quantification include

• 1. Pigmentation
• 2. Subcutaneous fat distribution / body composition

3 A l t t

• 3. Agonal temperature
• 4. Ambient temperature

Other supravital methods

• 1. Chemical or neuromuscular induction
• - iridial responsiveness to chemical stimuli

p

• - electrical stimulation of mimetic and thenar muscles
• 2. Ocular changes

l i

• - corneal opacity
• - segmentation (“boxcaring”) of retinal vessels

3 Transit time of gastric contents

• 3. Transit time of gastric contents
• 4. Vitreous analytes
• - K+
• - creatinine
• - urea / glucose
• - hypoxanthine / 3-methoxytyramine

Eye Changes

1 “B i ” f ti l l ½ h 1 “B i ” f ti l l ½ h

• 1. “Boxcaring” of retinal vessels ½ hr

eyes > open closed

• 1. “Boxcaring” of retinal vessels ½ hr

eyes > open closed

• 2. Corneal film mins

several hrs

• 3. Scleral discoloration

mins several hrs

• 2. Corneal film mins

several hrs

• 3. Scleral discoloration

mins several hrs

• 3. Scleral discoloration mins

several hrs

• 4. Corneal cloudiness < 2 hrs 12-24 hrs

5 C l it 3rd PM d

• 3. Scleral discoloration mins

several hrs

• 4. Corneal cloudiness < 2 hrs 12-24 hrs

5 C l it 3rd PM d

• 5. Corneal opacity 3rd PM day
• 5. Corneal opacity 3rd PM day

Food in Stomach Variations Variations

• Liquid faster than semisolid faster than solid
• Emotional state – psychogenic pylorospasm = delay
• Emotional state psychogenic pylorospasm

delay for several hours

• Hypermotility – 6-7 ft/hr…reaches cecum in 3 – 3.5

Hypermotility 6 7 ft/hr…reaches cecum in 3 3.5 hrs (normal = 6-8 hrs)

• CNS / spinal damage

p g

mol/L mmol/L K+ [mm K+ [m

Intermediate postmortem interval Intermediate postmortem interval

(days to weeks)

• Supravital changes at endpoint
• Greater emphasis on scene

Greater emphasis on scene

• Increased reliance on structural changes

Expect wider time brackets

• Expect wider time brackets
• Changes are more subjective / less

ifi bl quantifiable

Decompositional / Putrefactive changes

Slippage – Breakdown at intercellular junctions  Separation at papillary line Marbling - Heme degradation + H2S  Ferrous sulfide Bulla(e) – Capillary fluid / plasma between skin layers Bloating – Enteric anaerobes and facultatives ramp up fermentative rate. Increased rate of hydrolysis

• f protein, lipid, carbohydrate substrates

P fl id A t l i f GI d i t t t Purge fluid – Autolysis of upper GI and respiratory tracts

Slippage Bullae Bullae Marbling Bl ti Bloating Purge fluid

I t t ti bj t t Interpretation subject to:

Ambient temperature (Q10 rule) Ambient temperature (Q10 rule) Ambient moisture (Influence on bacterial activity) Age of individual (Development of enteric flora) Age of individual (Development of enteric flora) Agonal state (Fever, sepsis, dehydration) Altitude (Temperature PO2) Altitude (Temperature, PO2) Submerged Clothing Clothing Scavengers

Entomology Entomology

Coleopterids (Beetles)

Major issues have to do with

Collection in the field and at autopsy

• - Improper media or no media

Improper media or no media

• - Failure to adequately document temperature
• on body
• beneath body
• ambient

idi

“Garbage in,

Humidity Drugs on board ? Environmental features

Garbage out”

Environmental features

• Antagonistic species (e.g. fire ants)
• Plant suppressors (e.g. cedar, certain forbs)

pp ( g , ) Certified professionals only

Long Postmortem Interval

(Months to years) (Months to years)

• Usually involves skeletal or mummified remains

Usually involves skeletal or mummified remains

• Buried, submerged, scavenged
• Wide range estimates

Wide range estimates

• Greater emphasis on environmental information

and concurrence methods and concurrence methods

• Varies widely by biotic province
• Hampered heretofore by lack of understanding

Hampered heretofore by lack of understanding

• f long term changes
• How much gravitas should we give the

How much gravitas should we give the “body farms” ?

Pl t d M t Plants and Mycota

• - Leaf fall and seasonality
• - Root activity
• - Charging effects
• - Mold patches

Mold patches

• - Algal activity

Mycota

Adipocere formation

Mummification / Leatherization

“Wick” effect

PMI– Skeletal Remains

Chemical Methods

• Staining

Staining

• Loss of lipids
• Adipocere

Adipocere

• Carbonate

Physical Methods Physical Methods

• Specific gravity
• Sound transmission
• Sound transmission
• UV fluorescence
• Stable isotopes
• Stable isotopes

Other Other

• - Clothing fabric / associated artifact changes
• - Concurrence (e g coins in pocket environmental

Concurrence (e.g. coins in pocket, environmental correlates)

• - Relative dating (e g relation to construction)

Relative dating (e.g. relation to construction)

C ’ R l Casper’s Rule

“One week open exposure two weeks “One week open exposure = two weeks in water = eight weeks buried”… Although hardly accurate summarizes Although hardly accurate, summarizes the retarding effects of burial and i i d i i aquatic environments on decomposition.

Persistent Issues

• 1. When methods compete
• - Do rate methods and corporeal evidence
• - Do rate methods and corporeal evidence

trump concurrence and environmental data ? data ?

• - Is there a “hierarchy of methods”

2 Daubert challenges

• 2. Daubert challenges
• - Many methods not validated on adequate

samples or under varied conditions samples or under varied conditions

• 3. CSI effect
• - Is it “sciency”enough ?
• - Is it sciency enough ?
• - Common sense vs. rocket science

Rules you can live with y

• 1. There is no single accurate marker of time of death aside

from a credible witness or a reliable concurrence feature from a credible witness or a reliable concurrence feature.

• 2. Accuracy declines as interval lengthens.
• 2. Accuracy declines as interval lengthens.
• 3. Even with many variables accounted for, one should be

cautious, (We are a society addicted to data, but we don’t

• ften know how variables interact)
• 4. A range should always be given. A report of a “specific”

PMI is always suspect and so is its author PMI is always suspect, and so is its author.

• 5. An opinion must not exceed reasonable

interpretation of the data or the method.

• 6. Beware of predispositional bias, (e.g.

selection of methods or data that s pport selection of methods or data that support

• ne’s mind set.
• 7. Attempt to achieve convergence using methods

based on different premises. Wide discrepancies require an explanation 8 S l t t f ll

• 8. Select experts carefully.

9 Currently there is no unimpeachable way to determine

• 9. Currently, there is no unimpeachable way to determine

postmortem interval

“Pax ex jure et

Pax ex jure, et

jus per scientiam” j p

S l t d R di Selected Readings

• 1. The Human Skeleton in Forensic Medicine, 2nd ed. W.M. Krogman and M. Yasar Iscan
• eds. C.C. Thomas Co., 1986 (Ch 2) Good summary of methods for the longer interval.

, ( ) y g

• 2. Handbook of Forensic Pathology, 2nd ed. R.C. Froede ed. College of American

Pathology, 2003 (Chs. 7 and 8). Comprehensive but concise summaries of benchmark changes in bodies following death at various intervals changes in bodies following death at various intervals

• 3. The Estimation of the Time Since Death in the Early Postmortem Period, 2nd ed.
• C. Henssge, B. Knight, Thomas Krompecher, B. Madea, and L. Nokes, eds. Arnold Co.

2002 A good summary of various techniques, many experimental, for the short interval. Excellent bibliography. A useful guide to critiques of short interval estimates. 4 Forensic Taphonomy: The Postmortem Fate of Human Remains W D Haglund and

• 4. Forensic Taphonomy: The Postmortem Fate of Human Remains W.D. Haglund and
• M. Sorg eds. CRC Press 1997 Good survey of the effects of various environments on

rates of decomposition and skeletonization. Excellent bibliography.