individual review article: predicting the postmortem submersion interval for human remains recovered...
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A review on Heaton, V., Lagden, A., Moffatt, C., & Simmons, T. (2010). Predicting the postmortem submersion interval for human remains recovered from U.K. waterways. Journal of Forensic Science, 55(2), 302. PMSI and U.K. Waterways.pdf, and how this study can contribute to human remains recovery in an aquatic environment.TRANSCRIPT
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Individual Review ArticleMelissa Kimble
ANTH 410
Predicting the Postmortem Submersion Interval for Human Remains Recovered from U.K. Waterways, Heaton, V. , Lagden, A. , Moffatt, C. , & Simmons, T.
Estimating PMI (Post-Mortem Interval) is a critical focus within Taphonomy, due to the
intended ability to relatively date the time since death based on the rated sum of the visible stage
of decomposition within three regions of the body (Torso, face, and limbs). In 1992, Arpad A.
Vass determined that volatile fatty acids cease at a consistent interval and was able to produce a
“value” to determine the point at which all decomposition stops: 1285 +/- 110 ADD
(Accumulated Degree Days). Accumulated degree days are the sum of average daily temperature
in degrees Celsius that a body has been decomposing (and thus a fairly accurate determinate of
the time since death). In 2005, Mary S. Megyesi took this study by Vass, and used it to create a
“scoring” chart based on the visible stages of decomposition in how it related to the Post Mortem
Interval and ADD within reasonable accuracy. Accuracy was determined by comparing results of
the study to already determined rates of decomposition. There has been substantial research
involved in confirming ADD with terrestrial PMI, but because of the variables inherent in an
aquatic environment, “temperature, water depth, currents, tides, season, dissolved oxygen,
debris, substrate type, salinity, acidity, interactions between chemical and physical processes,
and insect and scavenging activity;” PMI as it relates to ADD in an aquatic environment has yet
to be established within reasonable acceptance and accuracy. Predicting the Postmortem
Submersion Interval for Human Remains Recovered from U.K. Waterways is an ethnographic
step in the right direction toward establishing PMI, or PMSI (Post-Mortem Submersion Interval)
in aquatic environments. The article itself focuses on calculating PMSI as it relates to ADD
based on data collected from closed case files, crime scene photographs and reports, and autopsy
files for a total of 187 cases that fell within the accepted criteria for the study. No actual
experimentation was conducted, but data was collected via gatekeepers and analyzed in detail.
This type of retroactive study, so long as the data accepted into the analysis had all required
criteria, is a valuable method for predicting PMSI because the subjects recovered essentially
worked as “controls” due to the already determined time of submersion to collection (which only
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included remains collected in waterways, and none that were swept to shore to maintain the
accuracy an aquatic decomposition).
In attempting to recover remains within aquatic environments, particularly the Trinity
River (which accounts for the majority of drowning within Humboldt county), evaluating studies
on PMSI as it relates to ADD can produce an interpolative study based upon the data to estimate
the time it would take for a body to reach the bloat stage based upon the parameters of local river
conditions. Upon drowning, the body submerges once the epiglottis relaxes and air is released
from the lungs and esophagus. As the body reaches the bloat stage of decomposition, it
reemerges but then deflates and sinks. It is the bloat stage that typically determines whether or
not remains can be recovered, so being able to accurately determine when this stage will be
reached is necessary for accurately determining when and where remains should be searched for.
One concern addressed in the article is that each waterway is unique, and should therefore be
assumed to produce data that cannot be translated into a universal constant. Species that live
within aquatic environments can typically only exist within a particular range of pH and
temperature, so a result showing that decomposition between waterways was found to be
relatively consistent and relatable to terrestrial decomposition should encourage further research
in this area, and not be assumed as coincidental.
Data that is primarily subjectively interpreted (the evaluation of PMSI based upon visual
stages of decomposition) is inherently biased, but continued tests to determine the accuracy of
PMSI in terms of ADD will only assist in establishing the range or lack of error in this type of
analysis. My primary issue with the analysis conducted was that individuals with a PMSI of 25
(the highest value you can obtain through visually scored stages) were non-existent, so values
were extrapolated based on the linear regression model developed from the analysis of the 187
cases discussed previously. Figures based on extrapolated values should rarely, if ever be
included into an analysis, because extrapolated values are typically unacceptable due to their lack
of acceptable accuracy. Only a substantial database of cases can increase the accuracy of this
study, and hopefully produce a future PMSI and ADD that can be repeatable and relatable to
future cases that include data on adipocere formation and how this affects aquatic decomposition
in detail.
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Bibliography
1. Heaton, V. , Lagden, A. , Moffatt, C. , & Simmons, T. (2010). Predicting the postmortem submersion interval for human remains recovered from U.K. waterways. Journal of Forensic Sciences, 55(2), 302.
2. Megyesi, M. , Nawrocki, S. , & Haskell, N. (2005). Using accumulated degree-days to estimate the postmortem interval from decomposed human remains. Journal of Forensic Sciences, 50(3), 618-617.
3. Vass, A. A., Barshick, S. A., Sega, G., Caton, J., Skeen, J. T., Love, J. C., & Synstelien, J. A. (1992). Decomposition Chemistry of Human Remains: A New Methodology for Determining the Postmortem Interval. Journal of forensic sciences, 47(3), 542-553.
4. Widya, M., Moffatt, C. and Simmons, T. (2012), The Formation of Early Stage Adipocere in Submerged Remains: A Preliminary Experimental Study. Journal of Forensic Sciences, 57: 328–333. doi: 10.1111/j.1556-4029.2011.01980.x
5. Drowning-related mortalities, deaths per day in the USA.(CDC, 2012) CDC. (2012). Retrieved from Centers for Disease Control and Prevention website: http://www.cdc.gov/homeandrecreationalsafety/water-safety/waterinjuries-factsheet.html
6. Drowning-related mortalities, deaths per day in the USA.(CDC, 2012) CDC. (2012). Retrieved from Centers for Disease Control and Prevention website: http://www.cdc.gov/homeandrecreationalsafety/water-safety/waterinjuries-factsheet.html
7. (Dahlberg, 2011) Dahlberg, C. P. (2011, June 30). Swift, cold and deadly. The Journal. Retrieved from http://www.northcoastjournal.com/news/2011/06/30/swift-cold-and-deadly/
8. (Mulligan, 2009) Mulligan, DR. (2009) Management of water incidents: drowning and hypothermia. Nursing Standard. 24, 7, 35-39. Date of acceptance: July 8 2009.
9. (Driscoll, Harrison & Steenkamp, 2004) Driscoll, T. R., Harrison, J. A., & Steenkamp, M. (2004). Review of the role of alcohol in drowning associated with recreational aquatic activity. Retrieved from http://www.ncbi.nlm.nih.gov/pmc/articles/PMC1730083/pdf/v010p00107.pdf