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Unit 9 Assignment B - Total Body Score and PMI
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Mollie McMillanEnvironmental Forensics
Unit 9
Assignment B
Total Body Score is when the level of decomposition is quantified in order to estimate the
time of death. It is when physical appearance is looked at too. When the body is observed,
the stage of decomposition can be given a score from 0-4, which then is able to give an
overall value.
Accumulated Temperature Effects and Accumulated Degree Days, this can demonstrate
how temperature (total amount of heat energy that has accumulated above a temperature
threshold after being deceased) affects decomposition rate, This can also be used alongside
entomology, to determine insect development to estimate time of death, for example, if an
adult blowfly is on a body, with no maggots present, you can determine the body is in the
first stages of decomposition as the insect colony present hasn’t become generational, it
relies on the fact that this is temperature-dependant. Samples of the insect can be collected,
and determine which generation of insect they’re in and how much they’ve developed. Then,
data collected from the temperature is used to calculate the ADD. This allows the PMI (post-
mortem interval) to be calculated by temperature and the effects of insect colonisation.
However, in order to improve these, different factors come into play such as if insects are
actually available or if there are many of them, temperatures can change this, therefore this
method may not be suitable if the temperature is too cold for example - as insects won't
survive as well or be as attracted to a decomposing body. This technique could be further
improved by taking into account body temperature compared to temperature of
surroundings, or used alongside other techniques.
Post-mortem interval is when the estimation of when a person died, after discovering the
body. This can be done in a variety of ways, such as: insect colonisation, humidity, soil
conditions. It allows forensic scientists to discern potential criminal activity after somebody
has died, and can help do things such as linking a potential suspect to their whereabouts at
the time a body died.
Time of Death is when it is determined all functioning of a biological organism has ceased,
including respiratory and circulatory systems, this also includes brain stem functioning. It can
be estimated using visual analysis on the body with decomposition stages, or things such
algor, rigor and livor mortis. Exact time of death may not be able to be found, however it is
still useful for analysing foul play.
● Appearance of the Body - Appearance of the body can help determine an estimation
on the time of death by analysing things such as Rigor Mortis, Livor Mortis and Algor
Mortis. This is when the body goes through different stages such as when all the
muscles go completely stiff and fixed within the position a person died - meaning
within a certain time frame this can disappear and you can determine an estimate
based on whether the body is in this stage or not. This is usually an early stage of
decomposition however, so if you find a body later, this may not be able to be used.
, You can also use the lividity of a body - whether the blood pooling within a cadaver is
fixed or not - for example if the body has been deceased for more than 12 hours,
discolouration will be fixed. You can also study the stages of decomposition -
whether the body is in initial decay or the dry stages, as a rough estimate on how
long the body has been deceased for. This can be seen through the changing
appearance of the body. You can also use the total body score to determine this and
secure the PMI. Without these techniques you may not be able to fully recognise
when a person has been deceased, therefore any type of foul play that may have
been done and the time it took place can’t be linked. Therefore if a suspect was seen
at a certain area at a certain time, you wouldn’t be able to link this as you don’t know
when the time of death has occurred based on the appearances.
● Differences in Environment - The different types of soil may affect time of death
estimation, for example, if a body is buried within brown earth's soil, the body may
decompose faster due to the chemical breakdown of the body due to high pH. This
can be useful because you can help change the estimation of time of death to be
longer or shorter based on the type of soil and take that into account for presenting in
court. Therefore whilst you can make more informed choices about whether time of
death is shorter or longer, based on the techniques, it can also be less reliable based
on usual readily available data such as Rigor Mortis occurring 5 hours after death, as
that can change. If a body is found in water - any type of onset of Rigor Mortis and
decomposition can be delayed and the body will cool quicker. As well as this, if a
body is left in the shade or out in the open sun can affect decomposition and different
techniques.
● Temperatures - Temperature can either accelerate or decelerate estimations on time
of death, in a warm environment, stages will happen faster, and Rigor Mortis will
develop and be completed faster, this means the usual estimate for Rigor Mortis
being completed has been changed - and therefore is less reliable for analysing time
of death. As well as this, if a body is found in a cooler environment, the
decomposition rates may be delayed or slowed down - such as the starts of states
such as Rigor mortis. If the environment is cooler, it may also become harder to use
body temperature, as it will cool quicker to the ambient temperature.
● Insect identification and development - You can use maggots and beetles to figure
out the stages of development of a decomposing body - you can do this by analysing
the outer shell of a maggot and analyse the age range with which an initial fly
developed - you can then use this to estimate a rough PMI, for example if the eldest
fly to develop and found on the body is 5 days old, you’ll know the body has been
decomposing for at least 5 days. Identifying the types of insects can change based
on the environment and the time the body has been deceased for, for example if a
rove beetle is found, they are typically found in the active decay stage, and
combining this with other factors, you can work out a PMI. Different insects can be
found at different scenes however, and environments, therefore insect types and how
the rate of development can change based on things like temperature should also be
taken into account. This method could be made more reliable on estimating time of
death by working with insects in different conditions - to improve research, and
seeing the rate of growth of insects in different locations.
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