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Professors, Student Study Pigs to Learn About
Decomposition Rates of Human Remains
RADFORD Investigating the cause of a human death can be like solving a puzzle.
Investigators face a plethora of challenging questions, which often lead to a complicated branch of new questions.
One question that must be answered is: When did the death occur?
For crime scene investigators and medical examiners, the answer depends greatly on decay rates of the victim, and those rates can vary given the influence of environment, climate and trauma to the body.
Radford University professors Cliff and Donna Boyd, along with senior Lindsay Sliwa, are conducting a pilot study to determine the variables of decay rates of human remains that have suffered blunt force and sharp-force trauma and those that have suffered no trauma.
“Does the existence of perimortem trauma on a body increase the decay rate and thus lessen the postmortem interval?” Donna Boyd asked. “How can we assess PMI when perimortem trauma to human remains is present? This is what we are trying to answer.”
To find the answers, the Boyds and Sliwa are using carcasses of stillborn pigs to serve as models of humans.
The research could not only provide valuable information to crime scene investigators who are charged with determining the time of death of a human corpse, but also, with the use of small stillborn pigs as models, make the research particularly applicable to identification and differentiation of trauma types in child abuse cases.
The Boyds and Sliwa will present their findings in February at the American Academy of Forensic Sciences annual meeting in Seattle.
Forensic anthropologists have previously suggested that human remains that display perimortem trauma, or trauma at the time of death, will decay faster than those remains that have not suffered either blunt force or sharp force trauma.
“Irregular or premature decomposition may occur due to an injury which exposes underlying tissue to decomposition agents,” Donna Boyd said. “There is also a possibility that previously unidentified trauma to human remains may be identified by differential decay. That is, when one portion of a human body shows more advanced decay than other portions, this may suggest the presence of perimortem trauma in that region.”
The study developed when Donna Boyd, a certified forensic anthropologist, asked her advanced forensics anthropology class to conduct a novel research project. Sliwa, who majors in anthropology, minors in biology and has an interest in human decomposition rates, proposed the study.
“Literature has already suggested that bodies with sharp force trauma will decay faster than those with no visible trauma, so we wanted to go one step beyond that and see how this decay rate would be affected if the bodies were buried,” Sliwa said. “Because there are so many factors involved, we worked with a few other professors, such as Dr. Rhett Herman in physics and Dr. Bob Sheehy in biology, to record as many of these factors and influences as we could.”
The Boyds, who serve as co-directors of RU’s Forensic Science Institute, obtained nine stillborn pigs from the Virginia-Maryland Regional College of Veterinary Medicine to conduct the research. Each pig was assigned a number and then weighed and measured for maximum length and width.
Three of the pigs were subjected to blunt force trauma, three others were subjected to sharp force trauma and the three remaining pigs were subjected to no trauma.
The pigs were then buried supine in burial pits, about 40 centimeters in depth, at RU’s Selu Conservatory. The researchers placed iButtons in each pig’s mouth to remotely monitor and record the temperature of the carcass every four hours. The Boyds and Sliwa also observed soil color and texture and collected soil samples at the burial sites.
After a month, pigs 1-3 were exhumed. The researchers recorded the stages of decay and then reburied the pigs. They conducted the same process with pigs 1-6 after 6 months, and after nine months, all of the pigs were disinterred to measure and compare rates of decay.
At the one month exhumation, the Boyds and Sliwa observed that pigs 1-3 had lost more than 35 percent of their body weight. Pig 1, the pig that suffered no trauma, had decomposed slower than pigs 2 and 3, while pig 3, the carcass that had suffered sharp force trauma, decomposed fastest and at a slightly faster rate than pig 2 which had suffered blunt force trauma.
Following the six-month disinterment, the researchers found that all of the pigs had skeletonized, leaving only a small portion of hair with the bones.
The experiments took place over the spring and summer and the Boyds also are conducting the same experiment in the fall and winter to observe and compare decomposition rates through the four seasons in the Southwest Virginia climate.
A third phase of the research will involve observing the skeletal remains of the pigs under a microscope to look for signatures of sharp force and blunt force trauma. Information stemming from this part of the project could be useful to investigators of pediatric violence.
“This pilot experiment demonstrated that it is possible to detect differences in decay rates between non-traumatized and traumatized buried remains,” Donna Boyd said. “Although sample sizes were small, pigs subjected to sharp-force trauma did show greater decay compared with the other pigs. In the future, experiments with larger sample sizes and more frequent disinterment and monitoring may enhance detection of variability in decay rates.”
Nov. 5, 2009