DEPARTMENT
OF ANATOMICAL SCIENCES
AN321
- FORENSIC OSTEOLOGY
TIME
SINCE DEATH
W.
B. Wood
Senior
Lecturer
The
University of Queensland
INTRODUCTION
It is important for the forensic pathologist or osteologist to provide
some estimate of the time since death of unidentified human remains so that the
police have some guidance as to when the person may have died or gone missing
and been reported to the Missing Persons Bureau.
Crucial to such a determination is evidence derived directly from the
remains as well as evidence from the recovery scene. Important details include
the location and disposition of the remains, whether open & exposed or
contained within an enclosed space, clothed or unclothed, wrapped, on the
surface, underwater, buried (and depth of burial), shaded or in sunlight,
ambient temperature, rainfall, vegetation, soil type, evidence of carnivours or
rodents (droppings, tracks) and whether the remains are compact or
scattered,etc.
The rate of decomposition is greatly accelerated by antemortem trauma,
the action of predatory carnivours and rodents, access to insects, and
particularly by high temperature and humidity. A recent report from Florida USA
stated that complete skeletonisation had been observed to occur in as little as
3-4 days after a body had been placed in a dump and covered by a vinyl sofa in
the middle of summer.
METHODS
Body Cooling:
In relatively recent death, evidence as to the time of death may be
provided by the degree of postmortem cooling of a body, and depends on the
ambient temperature, the presence or absence of clothing, and the degree of
obesity etc. As a rule of thumb, the body cools 1 1/2 degrees F per hour.
Livor Mortis & Rigor Mortis:
The presence of livor mortis and of rigor mortis also provide evidence
of relatively recent demise.
Livor mortis development begins immediately after death but does not
become apparent until about 2 hours after death. It reaches its maximum after
8-12 hours and after that time becomes fixed. During its development phase it
distribution may still change if the body is shifted. After 12 hours, any
movement or relocation of the body will not affect the distribution of the
lividity ie it has become fixed in position.
Rigor usually develops 2-4 hours after death and gradually disappears
after 36-48hours. The onset and duration is dependent on the ambient
temperature and the amount of oxygen debt of the muscles immediately prior to
death. Rigor mortis may appear almost immediately after death and disappear
within 9-12 hours in extremely hot environments or if the subject was suffering
from a generalised bacterial infection prior to death. Similarly its onset and
departure may be delayed in rapid cooling or freezing of the body after death.
Vitreous Humor:
The chemical constituents of the Vitreous Humor of the eye especially
the potassium level increase after death and have been used to estimate the
time interval since death.
Physical Examination of Remains
The rate and type of decomposition that is observed in a body also
provides evidence as to the time of death. However it is extremely sensitive to
a variety of intrinsic and environmental influences (Mann RW et al 1990)
the physical state of
the body at the time of death
thin and
emaciated - skeletonise faster
well
nourished - form adipocere
the presence of
antemortem trauma
the prevailing
temperature and humidity
the postmortem interval
before burial (if buried)
the influence of
clothing
the influence of any
other wrapping material (plastic, blankets etc)
the depth of interment
(in the case of burials)
soil type and pH
the presence of
decaying vegetable matter
access to insects
the influence of
scavengers eg dogs, rodents, foxes, wild pigs etc
The following features should be carefully noted in skeletonised
remains:
remnants
of soft tissue:
muscles,
ligaments, tendons, cartilage
skin
mummified
soft tissue
adipocere
hair &
fingernails
bone odour
(putrefaction) & a greasy feel
bone stains
weathering - bleaching,
surface flaking & cracking, chalkiness
bone erosion - due to
wind, sand, soil or water abrasion etc
bone invasion by
termites, rootlets
bone surface
colonisation by marine organisms (bryazoa, tubeworms, barnacles
rock boring sponges
etc.)
surface algae or mould
In the case of skeletal remains found on the surface, the presence of
putrefaction odour and a greasy feel of the bones indicates relatively recent
death, probably less than one year. For buried remains these signs may persist
for up to 5 years.
Evidence of weathering (ie bleaching, surface cracking and flaking, and
the development of a chalky appearance) usually takes two to five years to
develop in bones exposed on the surface.
Extensive scattering of skeletal remains (due to scavengers) usually takes
some years to occur.
Buried skeletons in a soil environment of pH <6 and with constant
percolating groundwater may completely disintegrate in about 5 years.
Chemical Examination of the
Bones
Changes in the organic constituents of the bones have been reported as
being useful in the determination of the time since death. The following
organic methods are probably the most useful but still have to be proven
reliable in their application to actual cases (Knight & Lauder 1969,
Facchini & Pettener 1977):
a) The benzedine test
if positive then probably < 150 years
b) Ultraviolet
fluorescence
if universally present then probably < 100 years
c) The number of
aminoacids in bone hydrolysate
if
> 7 then
probably < 100 years
d) Bone nitrogen level
if > 3.5g% then probably < 50 years
e) The presence of
prolines
if present then
probably < 50 years
f) Antihuman serum
reaction
if +ve then
probably < 5 years
Examination of Associated
Artifacts
Condition (and possible
dates) of:
clothing: types, material, quality, colour,
buttons
damage,
stains
laundry
marks
jewellery: finger rings, ear-rings, necklaces,
brooches, bracelets
glasses: type (bifocals etc), frame type
dentures: upper, lower, partial, complete,
composite material, ID number
leather: belts, handbags, shoes, wallets,
paper: banknotes, newspapers, licences,
receipts, tickets
plastic: bankcards
metal objects: buckles, penknives, zips, coins
Examination of environmental
evidence
insects: fly maggots (stage of development)
& pupae
beetles,
termites etc
vegetation: root invasion of bones
growth
or regrowth of damaged grass, shrubs etc
soil: buildup, erosion,
settlement in a grave, etc
weathering: bleaching of bones, surface
flaking of
cortical
bone
animal activity: evidence of bone scattering,
chewing
etc.
products of
decomposition:
volatile
fatty acid concentration within the underlying soil
Much research still needs to be done to refine methods of estimating
time since death. At the moment, most estimates are still only educated
guesses.
REFERENCES
Facchini F & D Patternur 1977 "Chemical and physical methods in dating human skeleton
remains." AJPA 47:65-70
Knight B & I Lauder 1969 "Methods of dating skeletal remains." Human Biol.
41:322-341
Mann RW, Bass WM & L Meadows 1990 "Time since death and decomposition of the human body:
variables and observations in case and experimental field studies." JFS
35(1):103-111
Smith KGV 1986 A Manual of Forensic Entomology. British Museum of Natural
History London