Estimating the Postmortem Interval using Soil Chemistry of Pseudomorphs. Stefanie M. Butera Department of Anthropology, University of South Florida

Transcription

1 Estimating the Postmortem Interval using Soil Chemistry of Pseudomorphs Stefanie M. Butera Department of Anthropology, University of South Florida (Advisor: Dr. E. Christian Wells; Committee member: Dr. Erin H. Kimmerle) Abstract: Phosphorus (P) derived from body decomposition is believed to produce burial silhouettes, or pseudomorphs, where the former body is outlined with a dark stain at the level of interment. It has been suggested that in sandy, acidic conditions, such as those that characterize many of Florida s soils, organic P complexes attract heavy metals, notably manganese (Mn), which result in dark stains. The phenomenon, however, is poorly understood. This project examines the formation and longevity of burial silhouettes from the perspective of simulated human burials using mock cadavers to determine how these deposits change over time. The greater goal of this effort is to improve predictive models for estimating time since death. Soils were sampled from six pig surface burials every 3 days over a period of one year, resulting in the collection of 432 soil samples. Chemical elements including P and Mn were extracted from samples with a mild acid extraction procedure, and the resulting extracts were characterized with appropriate reagents and a portable colorimeter. The resulting concentrations were examined using simple exploratory data analysis to explore how various local environmental conditions affect P and Mn chemistry over time.

2 Butera 2 Introduction: Forensic geoscience is described as a subdiscipline of geoscience that is concerned with the application of geological and wider environmental science information and methods to investigations which may come before a court of law (Pye and Croft 24:1). Forensic geoscience is a central area of interest that bridges geochemistry, geophysics, geoarchaeology, forensic pathology, entomology, and other natural science and investigation techniques utilized by legal professionals (Pye and Croft 24:2). Soil chemistry, also known as geochemistry, is a major component of forensic geoscience that analyzes the concentrations of certain chemical elements present in the soil that are involved with human decompositional processes. Sadly, the potential of forensic geoscience, mainly soil chemistry, is often overlooked by police and legal professionals (Pye and Croft 24:1). Due to the great variability in soil conditions, it is unknown why soil is not used more often as a defining characteristic in forensic situations. There is an enormous diversity among earth surface materials, and the fact that modern techniques are capable of very detailed characterization makes such material potentially highly useful in a forensic context (Pye and Croft 24:1). Methodology and techniques of forensic geoscience can be applied to a plethora of legal issues, from civil cases and environmental incidents to murder and terrorism (Pye and Croft 24:1). This project examines the formation and longevity of burial silhouettes in subtropical lowlands from the perspective of simulated human interments using pig cadavers to determine how these deposits change over time. The greater aim of this effort is to improve predictive models for estimating time since death in southern Florida to aid

3 Butera 3 forensic investigations. Another objective of this study is to increase awareness of soil chemistry and its potential in application to forensic cases. Background: In the article Review of human decomposition processes in soil (Dent et al. 24), the authors describe the process of decomposition. The authors describe the different rates of decomposition dependent on where a body is placed. The soil, being a complex assemblage of minerals, organic matter, salt and organic solutions and various microscopic and macroscopic organisms will exert varying influences in various locations and burial situations (Dent et al. 24:577). The article breaks down the steps of decomposition into putrefaction, liquefaction, disintegration, and skeletonization (Dent et al. 24:577). Exposure to oxygen increases the rate of decomposition since the bacteria initiating the putrefaction stage are aerobic (Dent et al. 24:577); therefore the model corpses used in my project would decompose at a much faster rate than that of buried remains, and would be greatly affected by the specific composition of the soil in the area which is directly impacted by water levels and temperature. Phosphorus is found in the body s nucleic acids, lipids, sugars, and enzymes (Dent et al. 24:58). As phosphorus is liberated during decomposition it does not follow simple pathways nor does it remain in its elemental form [its] oxidized forms appear to be tightly controlled by slight soil acidity (Dent et al. 24:58). The phosphate molecules are more stable in acidic conditions, making central-southwestern Florida s slightly acidic soil ideal for testing.

4 Butera 4 In Decomposition chemistry in a burial environment (Forbes 28a), the author elaborates on the processes involved in decomposition and states that Ultimately, the decomposition products will be released into the surrounding environment, which, in the case of a burial site, is the soil matrix (Forbes 2a8:217), then elaborating that the body type, physical characteristics of the burial environment, and the method of burial will also alter the rate of decomposition (Forbes 28a:217). The model corpses used in this project were all pig cadavers of similar size, about fifty pounds, and placed within a designated area. A section of Postmortem and postburial interval of buried remains (Forbes 28b) deals with chemical studies of soil in forensic anthropology. The author mentions an historical study measuring the amounts of nitrogen in long bones. It was shown that nitrogen has a progressive decrease with age and was not affected by the age of the individual at death (Forbes 28b:232). The nitrogen studies are not suited for specific dating, but rather distinguishing if remains are less than or more than one hundred years old (Forbes 28b:232). Amino acid studies were also preformed, but yielded similar results as nitrogen in terms of estimating time since death. In the 197s, studies involving immunological techniques began to develop (Forbes 28b:233). The percentage of fat content in remaining bone and histologic bone sections were attempted to be used but proved to be inaccurate. The first colorimetry studies were tested at this time, but not deemed reliable (Forbes 28b:233). Colorimetry technology has developed greatly since then and should prove to provide an accurate assessment for my research project.

5 Butera 5 Forensic soil chemistry has been gaining in popularity among researchers and law enforcement alike recently. Soil analysis in forensic taphonomy: chemical and biological effects of buried human remains by M. Tibbett and D.O. Carter and Geological and Soil Evidence: Forensic Applications by Kenneth Pye as well as articles by Arpad Vass are helping to put the field into the spotlight. High profile cases recently, like the Casey Anthony case, have also employed the usage of forensic chemistry. Methods: Six soil samples were collected from underneath four open-air model corpses (N, NE, NW, S, SE, SW) every 3 days for a period of six months, resulting in 144 samples. Each sample was taken from approximately the same locations each month using a corrosion-resistant, stainless steel hand auger (Picture 1), which was cleaned with water between sample collections. For each sample, 25-5 g of soil was collected and placed into sterilized polyethylene bags. A handheld GPS device with an accuracy of less than 1 m recorded the cadaver locations, and a grid was created for each pig using a measuring tape and compass. Picture 1 Phosphate (PO 4 3 ) and manganate (MnO 4 2 ) ions were extracted using a Mehlich II solution and Hach reagents. Two grams of soil were placed in a test tube with 2 ml of

6 Butera 6 Mehlich II extraction solution and agitated for five minutes. The sample was then filtered into a clean test tube (Picture 2). The extract was then diluted (1 ml extract to 9 ml Type II deionized water) into clean glass vials. For extractable P determination, the contents of a Phos Ver 3 powder pillow was added to the solution and dissolved. For extractable Mn determination, the contents of a citrate type buffer powder pillow were added and dissolved, followed by a sodium periodate powder pillow. For both analyses, after waiting five minutes for the reagent to react, the solution was analyzed using a portable Hach DR 85 colorimeter. Picture 2 Picture 3 Data: Samples were taken from six positions around each of the four cadavers. A North sample was taken from the head region, South from the lower extremities region, with a Northeast, Southeast, Northwest, and Southwest, respectively. The sample of the cadavers BH3, BH4, and BH5 were used for analysis. The concentration results of the phosphate analysis and the manganate analysis were graphed over time for 18 days. The resulting graphs are below.

7 Butera 7 Figure 1: Cadaver 3 (BH3) Phosphate Results Cadaver 3 (BH3).9.8 Phosphate Concentration mg/l N NE NW S SE SW Time Elapsed in days Figure 2: Cadaver 3 (BH3) Manganese Results Cadaver 3 (BH3) Manganese concentration mg/l N NE NW S SE SW Time elapsed in days

8 Butera 8 Figure 3: Cadaver 4 (BH4) Phosphate Results Cadaver 4 (BH4) 1.9 Phosphate Concentration mg/l N NE NW S SE SW Time Elapsed in days Figure 4: Cadaver 4 (BH4) Manganese Results Cadaver 4 (BH 4) 1.4 Manganese Concentration mg/l N NE NW S SE SW Time Elapsed in days

9 Butera 9 Figure 5: Cadaver 5 (BH5) Phosphate Results Cadaver 5 (BH5).9.8 Phosphate Concentration mg/l N NE NW S SE SW Times Elapsed in days Figure 6: Cadaver 5 (BH5) Manganese Results Cadaver 5 (BH5) Manganese Concentration mg/l N NE NW S SE SW Time Elapsed in days

10 Butera 1 Chart 1: Phosphate (P) Data Summery Cadaver Mean Median Mode SD Variance CoV BH BH BH Chart 2: Manganese (MN) Data Summery Cadaver Mean Median Mode SD Variance CoV BH BH BH BH Results: Phosphate Comparison: The phosphate values from the data were compared with the samples taken from each specific area (direction) of each cadaver. The resulting graphs are below. Figure 7: Samples From North End of Cadavers.9.8 Phosphate Concentration mg/l BH3 BH4 BH Time Elapsed in days

11 Butera 11 Manganese Comparison: The manganate values from the data were also compared with the samples taken from each specific area of each cadaver. The resulting graphs are shown below. Figure 8: Samples From North End of Cadavers 1.4 Manganese Concentration mg/l BH3 BH4 BH Time Elapsed in days Figure 9: Samples From Northeast End of Cadavers 1.6 Manganese Concentration mg/l BH3 BH4 BH Time Elapsed in days

12 Butera 12 The phosphate ions seem to reach their peak concentration between 6 and 9 days (Figure 7, Figure 1, Figure 11, Figure 12). The manganate ions then reach their peak between 9 and 12 days (Figure 8, Figure 9). This suggests that the phosphate reaction cycle must complete or be near completion before the manganate cycle can peak. After peaking, the phosphate ion concentrations decrease, but in no patterned order. The manganate ions seem to rise again around 15 days, but there does not appear to be a consistent pattern in the samples. The Northeast sample phosphate values Cadaver 5 (BH5) (Figure 1) did not fit into this pattern. The phosphate level peaked at around 12 days. The concentration peak was nearly double the Northeast sample values of Cadavers 3 and 4 (BH3, BH4) (Figure 1). Figure 1: Samples From Northeast End of Cadavers.8.7 Phosphate Concentration mg/l BH3 BH4 BH Time Elapsed in days This same discrepancy occurred in the Southeast samples of Cadaver 4 (BH4) and the Northwest samples of all three cadavers.

13 Butera 13 Figure 11: Samples From Southeast End of Cadavers Phosphate Concentration mg/l BH3 BH4 BH Time Elapsed in days Figure 12: Samples From Northwest End of Cadavers.6 Phosphate Concentration mg/l BH3 BH4 BH Time Elapsed in days The Northeast, Northwest, and Southeast sample sets (Figure 1, Figure 11, Figure 12) are further away from the midline of the cadaver than the North ad South sample. This could suggest that the reaction cycle occurs more slowly in the outer samples versus the sample taken from

14 Butera 14 directly under the cadaver. In the South sample of Cadaver 5 (BH5) (Figure 13), however, the peak in concentration is sharp and occurs at 12 days. Figure 13: Samples From South End of Cadavers 1.9 Phosphate Concentration mg/l BH3 BH4 BH Time Elapsed in days It is possible that error occurred during the analysis of the South sample: 12 days of Cadaver 5 could account for the result. Discussion: The results of this study seem to suggest that phosphate and manganate enter the soil record through the decomposition process of the model corpses, and that these analytes have patterned depositions over time. The phosphate peaks between 6 and 9 days and the manganate ions then reach their peak between 9 and 12 days. The behavior outside of these parameters seems to have some sort of pattern, but it is inconclusive at this time. Further study would be required to discover the nature of the sharp phosphate peaks on the outer samples and the secondary peaks of the manganate ions.

15 Butera 15 Patterned cycles could be incredibly useful in forensic study. Further research could possibly be able to map exactly which ions peak at which times and develop a sort of guideline for estimating time since death based on only the soil. This could be incredibly useful especially in cases where the remains are moved. Future studies could include analysis of other potential patterning cycles. Tracking humidity, temperature, and ph could also lead to a more developed conclusion.

16 Butera 16 References Dent, B.B, S.L Forbes, and B.H. Stuart 24 Review of human decomposition processes in soil. Environmental Geology 45: Forbes, Shari L. 28a Decompostition chemistry in a burial enviornment. In Soil Analysis in Forensic Taphonomy, by S. L. Forbes, pp CRC Press, Boca Raton, Florida. Forbes, Shari L. 28b Postmortem and postburial interval of buried remains. In Soil Analysis in Forensic Taphonomy, by S. L. Forbes, pp CRC Press, Boca Raton, Florida. Pye, Kenneth and Debra Croft 24 Forensic geoscience: introduction and overview. In Forensic Geoscience Principles, Techniques, and Applications, by K. Pye and D. Croft, pp 1-5. Geological Society, London.

17 Butera 17 Appendix A Phosphate Raw Data Pig Date Sample P PO4 BH3 1/3/26 N.3.92 BH3 1/3/26 NE.3.93 BH3 1/3/26 NW BH3 1/3/26 S BH3 1/3/26 SE BH3 1/3/26 SW.33 1 BH3 12/1/26 N BH3 12/1/26 NE.9.28 BH3 12/1/26 NW BH3 12/1/26 S BH3 12/1/26 SE BH3 12/1/26 SW.9.29 BH3 1/12/27 N BH3 1/12/27 NE BH3 1/12/27 NW BH3 1/12/27 S BH3 1/12/27 SE BH3 1/12/27 SW BH3 2/9/27 N BH3 2/9/27 NE BH3 2/9/27 NW BH3 2/9/27 S BH3 2/9/27 SE.3.93 BH3 2/9/27 SW BH3 3/27/27 N BH3 3/27/27 NE BH3 3/27/27 NW.3.93 BH3 3/27/27 S BH3 3/27/27 SE.3.91 BH3 3/27/27 SW BH3 8/24/27 N BH3 8/24/27 NE BH3 8/24/27 NW BH3 8/24/27 S BH3 8/24/27 SE BH3 8/24/27 SW BH4 1/3/26 N BH4 1/3/26 NE BH4 1/3/26 NW.27.8 BH4 1/3/26 S.23.7 BH4 1/3/26 SE BH4 1/3/26 SW BH4 12/1/26 N BH4 12/1/26 NE BH4 12/1/26 NW.31.95

18 BH4 12/1/26 S BH4 12/1/26 SE BH4 12/1/26 SW BH4 1/12/27 N BH4 1/12/27 NE.14 2 BH4 1/12/27 NW BH4 1/12/27 S.65 2 BH4 1/12/27 SE.14 4 BH4 1/12/27 SW.1.29 BH4 2/9/27 N BH4 2/9/27 NE BH4 2/9/27 NW BH4 2/9/27 S BH4 2/9/27 SE BH4 2/9/27 SW BH4 3/27/27 N BH4 3/27/27 NE BH4 3/27/27 NW BH4 3/27/27 S BH4 3/27/27 SE BH4 3/27/27 SW BH4 8/24/27 N BH4 8/24/27 NE.13 1 BH4 8/24/27 NW.2.62 BH4 8/24/27 S BH4 8/24/27 SE BH4 8/24/27 SW BH5 1/3/26 N.16 9 BH5 1/3/26 NE BH5 1/3/26 NW BH5 1/3/26 S.23.7 BH5 1/3/26 SE BH5 1/3/26 SW.23.7 BH5 12/1/26 N BH5 12/1/26 NE.3.91 BH5 12/1/26 NW.15 7 BH5 12/1/26 S BH5 12/1/26 SE.2.61 BH5 12/1/26 SW BH5 1/12/27 N 1.22 BH5 1/12/27 NE BH5 1/12/27 NW BH5 1/12/27 S BH5 1/12/27 SE BH5 1/12/27 SW BH5 2/9/27 N BH5 2/9/27 NE BH5 2/9/27 NW BH5 2/9/27 S BH5 2/9/27 SE Butera 18

19 BH5 2/9/27 SW BH5 3/27/27 N BH5 3/27/27 NE.23.7 BH5 3/27/27 NW 1.24 BH5 3/27/27 S BH5 3/27/27 SE.3.92 BH5 3/27/27 SW BH5 8/24/27 N BH5 8/24/27 NE.15 7 BH5 8/24/27 NW BH5 8/24/27 S.1.29 BH5 8/24/27 SE BH5 8/24/27 SW Butera 19

20 Butera 2 Appendix B Manganese Raw Data Pig Date Sample Mn MnO4 BH3 1/3/26 N BH3 1/3/26 NE BH3 1/3/26 NW BH3 1/3/26 S.8 BH3 1/3/26 SE BH3 1/3/26 SW BH3 12/1/26 N.3.6 BH3 12/1/26 NE BH3 12/1/26 NW BH3 12/1/26 S.2.5 BH3 12/1/26 SE BH3 12/1/26 SW.8 BH3 1/12/27 N BH3 1/12/27 NE.9 2 BH3 1/12/27 NW.9 BH3 1/12/27 S.1.3 BH3 1/12/27 SE.3.7 BH3 1/12/27 SW.1.2 BH3 2/9/27 N.1.8 BH3 2/9/27 NE BH3 2/9/27 NW 1 BH3 2/9/27 S.3.6 BH3 2/9/27 SE BH3 2/9/27 SW.2 BH3 3/27/27 N.9 BH3 3/27/27 NE BH3 3/27/27 NW.5 1 BH3 3/27/27 S.2.5 BH3 3/27/27 SE.2.5 BH3 3/27/27 SW.1.2 BH3 8/24/27 N BH3 8/24/27 NE BH3 8/24/27 NW BH3 8/24/27 S BH3 8/24/27 SE BH3 8/24/27 SW BH4 1/3/26 N BH4 1/3/26 NE.5 1 BH4 1/3/26 NW.5 1 BH4 1/3/26 S.2.5 BH4 1/3/26 SE BH4 1/3/26 SW.8 BH4 12/1/26 N BH4 12/1/26 NE BH4 12/1/26 NW.7 1.4

21 BH4 12/1/26 S.1.2 BH4 12/1/26 SE.8 BH4 12/1/26 SW BH4 1/12/27 N BH4 1/12/27 NE BH4 1/12/27 NW BH4 1/12/27 S BH4 1/12/27 SE.9 BH4 1/12/27 SW BH4 2/9/27 N.3.6 BH4 2/9/27 NE.3.7 BH4 2/9/27 NW.8 BH4 2/9/27 S BH4 2/9/27 SE.5 1 BH4 2/9/27 SW BH4 3/27/27 N BH4 3/27/27 NE BH4 3/27/27 NW.8 BH4 3/27/27 S.3.6 BH4 3/27/27 SE BH4 3/27/27 SW.9 2 BH4 8/24/27 N.2.5 BH4 8/24/27 NE.3.5 BH4 8/24/27 NW.1.1 BH4 8/24/27 S.2.5 BH4 8/24/27 SE BH4 8/24/27 SW.2.5 BH5 1/3/26 N.9 BH5 1/3/26 NE BH5 1/3/26 NW BH5 1/3/26 S BH5 1/3/26 SE.9 2 BH5 1/3/26 SW BH5 12/1/26 N BH5 12/1/26 NE.3.6 BH5 12/1/26 NW 1 BH5 12/1/26 S BH5 12/1/26 SE BH5 12/1/26 SW BH5 1/12/27 N BH5 1/12/27 NE BH5 1/12/27 NW BH5 1/12/27 S.8 BH5 1/12/27 SE BH5 1/12/27 SW.9 2 BH5 2/9/27 N BH5 2/9/27 NE.9 BH5 2/9/27 NW BH5 2/9/27 S BH5 2/9/27 SE Butera 21

22 BH5 2/9/27 SW BH5 3/27/27 N BH5 3/27/27 NE.9 2 BH5 3/27/27 NW.5 1 BH5 3/27/27 S BH5 3/27/27 SE BH5 3/27/27 SW BH5 8/24/27 N.5 1 BH5 8/24/27 NE BH5 8/24/27 NW BH5 8/24/27 S.9 BH5 8/24/27 SE BH5 8/24/27 SW.3.7 BH6 1/3/26 N BH6 1/3/26 NE.3.6 BH6 1/3/26 NW BH6 1/3/26 S.9 2 BH6 1/3/26 SE BH6 1/3/26 SW BH6 12/1/26 N.9 BH6 12/1/26 NE BH6 12/1/26 NW.8 BH6 12/1/26 S BH6 12/1/26 SE.3.6 BH6 12/1/26 SW BH6 1/12/27 N BH6 1/12/27 NE.3.6 BH6 1/12/27 NW BH6 1/12/27 S BH6 1/12/27 SE.1.3 BH6 1/12/27 SW BH6 2/9/27 N BH6 2/9/27 NE BH6 2/9/27 NW BH6 2/9/27 S.3.7 BH6 2/9/27 SE.3.7 BH6 2/9/27 SW.9 BH6 3/27/27 N.9 2 BH6 3/27/27 NE.2.3 BH6 3/27/27 NW.2.5 BH6 3/27/27 S.1.2 BH6 3/27/27 SE.2.5 BH6 3/27/27 SW.1.3 BH6 8/24/27 N BH6 8/24/27 NE BH6 8/24/27 NW.2.5 BH6 8/24/27 S.8 BH6 8/24/27 SE BH6 8/24/27 SW.9 Butera 22

23 Butera 23 Appendix C Maps of Cadaver Locations

24 Butera 24