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Introducing Geotaphonomy to the Archaeologist and Crime Scene Reconstructionist Special Agent Mike Hochrein Federal Bureau of Investigation, St. Louis, Missouri The Midwest Bioarcheology and Forensic Anthropology Association 9th Annual Meeting October 19, 2002 Indianapolis, Indiana Abstract

The concept of geotaphonomy is presented for anthropologists, law enforcement, medico-legal, and other crime scene investigators as a means of recognizing contextual environmental clues within and around buried evidence scenes. Geotaphonomy is defined as the study of the geophysical characteristics of, and changes in, surface to subterranean features associated with the interment of buried evidence. It represents a tool for investigators who seek to reconstruct how, when, and by whom clandestine burials were created. Borrowing from taphonomy, geotaphonomy examines the pit, (the body), for evidence of ante-depositional (ante-mortem), peri-depositional (peri-mortem), and post-depositional (post-mortem), modifications. Six aspects of burial environments comprise the theory of geotaphonomy. Each are mentioned with their particular collection of geological, pedological, criminalistic, and biological categories of evidence. It has been the author's observation that these are areas which are typically overlooked or ignored during sometimes overzealous efforts to reveal and extract the primary piece of buried evidence. This paper briefly introduces the potential quantity and quality of geotaphonomic evidence associated with clandestinely buried items. Introduction

Buried evidence scenes can range from those as inert as the hidden money from a bank robbery to those as biologically and emotionally volatile as the remains of an abducted child. They each require the application of formal archaeological techniques to fully understand the circumstances surrounding their burial. Too often the phrase "archaeological excavation" is used by law enforcement and media in describing untrained or minimally trained personnel using shovels or grosser equipment to dig up forensically significant evidence. The use of archaeologists by law enforcement, if at all, has been reserved for the recovery of human remains. Even then, archaeologists and physical anthropologists, whether or not they have been forensically trained may not realize the full potential that the clandestine grave or pit itself might offer. That potential lies in characteristics created as a pit is dug, filled, and sits over days or decades. In

order to identify and record those characteristics as evidence of how the burial feature came to be and changed over time, archaeologists can borrow from the discipline of taphonomy. Developed by paleontologists and refined by physical anthropologists, taphonomy was originally and generally defined as processes by which animal and plant remains become fossilized. As it applies to forensic settings, Haglund and Sorg (1997: 3) write:

"Forensic taphonomy refers to the use of taphonomic models, approaches and analyses in forensic contexts to estimate the time since death, reconstruct the circumstances before and after deposition, and discriminate the products of human behavior from those created by the earth's biological, physical, chemical, and geological subsystems."

Forensic geotaphonomy, as presented here and in previous works, (Hochrein, 1997a; 1997b; 2000; and 2002), (Haglund and Sorg, 1997 and 2002), is defined as the study of the geophysical characteristics of, and changes in, surface to subterranean features associated with the interment of buried evidence. The concept of forensic geotaphonomy developed out of a realization that investigators of clandestine grave, or other buried evidence crime scenes, lacked precedents demonstrating the possible geophysical features or conditions which could aid in interpreting subterranean scenes. Although they are seldom noticed at contemporary crime scenes, many of these conditions are the bases of archaeological tenets. In geotaphonomy the features comprise six areas or classes of evidence which are introduced during and after the original excavation and backfilling of subterranean pits. The six classes of geophysical evidence include stratification, tool marks, bioturbation, sedimentation, compression/depression, and internal compaction.

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Figure 1: A stratigraphic profile in a mid-19th century cemetery showing the intrusion of grave shafts through the natural stratification; stratification within the grave shafts; and cultural stratification which formed above the level at which the graves were dug.

Stratification

Stratification and the concept of stratigraphy need little elaboration for archaeologists and geologists. The premise of locating subterranean features through the recognition of changes in naturally or culturally formed layers of soils across a given area has been used for hundreds of years to locate and interpret prehistoric and historic sites (Figure 1). Stratigraphy should first be considered at buried evidence crime scenes during the search phase of the crime scene investigation. Both the search and recovery phases can utilize archaeology to assess stratigraphic anomalies. Those assessments include deciphering gross stratification across a search area in order to delimit anomalies which might represent clandestine pits. Following their discovery, most crime scene reconstructionists, however, do not realize the value of stratigraphy within the pit's fill, assuming the contents represent a single depositional event. In reality each shovel full of backfilled dirt leaves a signature lens which may be visible in cross-section during archaeological excavation (Figure 2). Additionally, nonhuman and human animal intrusions into a pit for scavenging or attempted relocation of the evidence may also be recognized in modified stratification (Figures 3a and 3b). In general, stratification within the pit can help investigators to understand:

1) the backfilling process (i.e. the addition of foreign elements such as a body, lime, concrete, et cetera);

2) the types of instruments used to backfill the pit (i.e. a shovel versus a backhoe);

3) the relationship of in situ evidence to depositional events; and

4) post-depositional events such as attempts to remove and relocate a body.

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Figure 2: Micro-stratigraphy revealed in profile during the excavation of a clandestine grave found to contain four homicide victims.

The archaeologist's expertise in recognizing and interpreting stratigraphy can serve investigators by proving that evidence was not, and could not, have been buried at a particular site. This "negative", or absence of, evidence has been used in convicting individuals who provided false statements in attempts to obstruct an investigation. In

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Figure 3a: Crime scene diagram depicting the plan view and profile of a grave containing two homicide victims wrapped in a tarpaulin and discovered one year after their disappearance Figure 3b: A stratigraphic profile above the remains, (southwest quadrant facing east), showing an interruption to the stratification consistent with information that suspects returned to the grave site and attempted, but abandoned, the removal and relocation of the bodies.

In 1999 Local, State, and Federal investigators were led on a series of "wild

goose chases" by a suspect who repeatedly pledged his cooperation in locating the body of a teenage girl who had been missing since 1989. Archaeological excavation of one scene in particular was used toward the indictment and conviction of the suspect for providing false statements to Federal investigators in violation of Title18 Section 1001 of the United States Codes. That excavation revealed undisturbed stratification and tool mark evidence which proved that a trench had been dug by a bulldozer in the area specified by the suspect; however, the same geotaphonomic evidence demonstrated that the trench was never deep enough to have completely concealed the container in which the victim's body was alleged to have been buried.

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Figure 4: Closeup view of a shovel handle impression created during the excavation of a pit Tool Marks

Tool marks are routinely sought by criminalists processing burglary and bombing scenes or while examining ballistics evidence from above ground settings such as buildings and cars. Efforts to identify the types of tools used to dig forensically significant pits, however, are often overlooked or ignored because of poor excavation techniques or a resignation to ill-founded predictions that tool marks could not have survived the days, weeks, or years that may have passed since the pit was dug and filled. Certainly, tool marks may not be evident in every soil-type or around the entire perimeter of a pit, but every scene should be approached as if such evidence could have survived. Generally rocky or sandy soils will not hold marks as well as those with higher clay-silt contents. Even though they may not be clearly visible, they must exist in as much as a manmade pit could not be created without some type of instrument scratching or pressing into the soil in which the pit intrudes. Fortunately, much of the

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United States is covered by higher clay content soils which tend to hold the friction and impression detail examined by tool mark specialists. Hochrein (1997b) describes the variety of marks which might be left in buried evidence scenes and which can be cast after exposure through careful excavation (Figure 5).

The casting process uses dental gypsum in the manner shoe and tire impressions are cast. In an archaeological setting, however, the tool mark is uncovered through traditional excavation techniques and then cleaned through vacuuming before casting. This protocol reveals striae which are unique to the particular instrument which made them. Photographing and casting that detail before it has an opportunity to dry and crack preserves such individual characteristics for the tool mark examiner. At a minimum, the crime scene archaeologist should be able to locate and record information identifying the class of tool used to create a pit. The importance of such information lies in its ability to shed light on:

1) the number of tools used in an excavation, potentially for indicating the number of individuals involved in creating the pit;

2) the direction of excavation or other characteristic digging techniques associated with one or possibly more individuals; and

3) the types of tools and depth of excavation which could imply a suspect's intent as reflected in the extent of planning involved in carrying out the crime (i.e. a shallow grave dug with a crowbar would be more indicative of a spontaneous disposal or concealment versus a deep shaft excavated with a rounded blade shovel.)

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Figure 5: A dental gypsum cast of a maddock tool mark including the friction detail of the horizontal blade and impression detail of the vertical blade. Bioturbation

Bioturbation, like stratification, is a well known concept among archaeologists and geologists. Simply stated, bioturbation consists of the effects of animals and plants on the creation and history of subterranean features. Plants impact burials and clandestine pits in the manner and rate which root systems grow through the pit and its contents. Dendrochronology of roots (Figure 6) can be used to provide a time frame during which the evidence was deposited. The condition of the roots, in recent burials in particular, may offer indications as to the general class of tool(s) used to dig the grave. Broad-bladed instruments like curved or flat shovels tend to sheer roots at the walls of a pit. Thin profile tools such as pitchforks, crowbars, and screwdrivers leave the roots intact creating a lattice, or network of roots, on which a buried piece of evidence might be placed before the pit was backfilled. The condition of buried vegetation, (the green of leaves and grass in a freshly filled grave), or its position within a pit, (Fall leaves settling at the base of a grave before the body is placed within it), can also provide investigators with valuable clues of when the pit was dug and filled. Pollen from plants surrounding the burial site adhere and may survive indefinitely on a suspect's clothing, tools, or the vehicles and furniture onto which it might be transferred. The botanist/palynologist must work in concert with other crime scene investigators in recording both surface and subterranean plant evidence at these sites.

Figure 6: A quarter thin section slide made of a tree root which grew through a clandestine grave immediately across the femurs of the skeletal remains of a victim's skeleton.

Animals such as gophers, mice, voles, and other burrowing species obviously impact burial features over time. Active burrows as well as krotovinas can help to explain the position or absence of evidence. They provide the processors of crime scenes with avenues by which burrowing animals may have carried away small skeletal elements, jewelry, hairs and fibers, et cetera. Evidence of large scavenging carnivores such as coyotes, wolves, or domestic dogs may be archaeologically associated with disposal sites by their digging modifications to the grave. The archaeologist with the assistance of naturalists or conservation agents should be able to identify features created by scavengers attempting to dig into a grave. Those features might otherwise be interpreted, over time, as secondary depressions or human attempts to uncover remains for relocation, souvenirs, or other reasons. Fur or hair, animal tracks, and scat deposits are other forms of evidence which might accompany nonhuman animal bioturbation. Recognizing and mapping bioturbation evidence can provide the following information:

1) clues to a clandestine pit's chronology;

2) indications of the type(s) of tools used to dig a pit.

3) possible avenues to search for missing evidence, or explanations for repositioned items.

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Figure 7a: Crime scene diagram depicting the position of a shallow buried homicide victim Figure 7b: The foot, or west, end of the burial, (facing west), located by archaeological excavation and revealing intruding animal krotovinas (a-d) Sedimentation −9−

Sedimentation might be included under "Stratification" but here is distinguished

from the basic principles of layering. Its importance here lies in what happens after the layer of sediment forms within an open pit and/or on top a backfilled pit. Like many of the other categories of geotaphonomic evidence, sedimentation can help to reconstruct the chronology of events associated with the burial feature. Within the pit, evidence of sedimentation across its bottom would be evidence that rainfall occurred sometime after the pit's excavation but before it was backfilled. The formation of cracks in that layer of sediment may indicate that at least twelve hours lapsed after rainfall caused the sediments to form the layer at the base of the pit. Like tool marks, buried evidence of sedimentation in the form of subsurface cracking, can be recovered through careful excavation and cleaning via vacuum (Figure 8).

Figure 8: Subsurface cracking in a test pit before backfilling (left) and as revealed after partial archaeological excavation 30 days after the pit was backfilled (right).

On the surface of a clandestine pit, peripheral cracking along the edge of a pit is often used during the search phase of a crime scene investigation to help identify some burial sites. Such cracking is evidence of pit-type excavations as opposed to the more random spider web type pattern which occurs in sediments drying at the base of shallow pools. At scenes located on active flood plains, the presence and number of sediment layers, or strata, define individual flooding episodes. These may be matched to historically recorded river stage data to determine how many floods occurred since the evidence was disposed at the site. Within the pit, the formation of a sediment layer

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followed by its cracking could only occur if the pit laid open long enough for rain water to collect, throwing soil particles into suspension which settle as a fine sediment layer. Additional time is then needed for the water to drain and the sediment layer to dry sufficiently to crack. The implication is that the digging of a pit well before the body or other evidence is placed inside supports contentions that intent and planning went into the criminal act. Surface to subsurface evidence of sedimentation can potentially offer the following information about the setting of a forensically significant concealment:

1) clues to the pit's chronology;

2) an indication of ante- and peri-depositional rainfall at the burial site; and

3) evidence of flooding episodes in flood plain settings.

Figure 9: Example of compression evidence in the form of a fabric impression left by an individual kneeling near buried items believed associated with a homicide. Compression and Depression

The category of compression and depression evidence suggests two reasons for the occurrence of changes to the surface contour of a pit over time. First, the intentional compression of backfill in a pit including shoe prints, knee prints (Figure 9), tire impressions, or perhaps tool marks left by the slapping of a spade against the surface −11−

of the backfilled pit. The suspect excavator realizes that he cannot mound earth over a clandestine pit and wait for it to settle over time. Rather, suspects may tamp or step fill to the same grade as undisturbed ground surfaces in order to hide the existence of a pit. The action of such compression not only imparts impression evidence to the scene, but also impacts the second part of this geotaphonomic category - depression evidence.

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Figure 10a-c: Primary and secondary depressions (bottom) formed in a test pit containing two wrapped pigs (top left and right), approximately six months after their burial.

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Depression evidence consists of changes in surface contours over a clandestine

burial through the natural settling and decompositional changes in a pit's contents (Figure 10). One of the first signs search personnel are told to look for during pedestrian walkovers of a possible clandestine grave crime scene is the depressed area of a pit which has been backfilled and then settled over time. The depression is enhanced because of a suspect's need to level the surface over the pit after burial in order that it looks flat and therefore undisturbed. Additionally, there may be too little backfill to completely refill the pit in spite of the addition of the body or other evidence. The general settlement of a pit's fill is referred to as the primary depression. In situations where a body is the buried evidence, certain conditions may result in a secondary depression. Where a body is buried face-up in a shallow grave, the abdominal area may bloat, collapse upon decomposition causing the overlying soil to sink into the voided area. The same process occurs with evidence buried in containers which corrode or rot over time and collapse into themselves.

An understanding of compression and depression evidence at a burial scene may enhance a crime scene investigation as:

1) an aid in identifying shoe print and other impression evidence discussed above;

2) a field indicator for search parties of a potential burial; and

3) as a rudimentary indicator of the length of time since burial.

Internal Compaction

Internal compaction is the last and least explored area of geotaphonomy. The concept was realized during the 1988 case of serial murderer Dorothea Montalvo Puente. Puente, known as the "Sacramento Boarding House Murderer" was convicted of killing seven elderly men and women who last stayed at her home/boarding house (Wood, 1994). In the course of reviewing crime scene photographs investigators noticed what might have been evidence of the victim's movement within one of the graves:

"City homicide investigator John Cabrera 'believed, and the anthropologist agreed it was possible , that Martin had awakened from her drugged stupor and begun jerking her wrapped legs, trying to kick to the sides or above her,' Wood wrote.

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Cabrera found that the struggle had left 'an unusual compaction of dirt on either side of the victim's wrapped legs and a mound-like effect above the knees, as if the soil had been forced upward,' creating a tunnel in the otherwise loose soil, Wood said."

(Wilson, 1994:A-4) In that case the possibility existed that the victim and perhaps others could have been buried alive in as much as Puente preferred to dispatch her victim's by first overdosing them with medication. In cases where the victim's remains are sufficiently decomposed or wrapped thus preventing a determination of whether or not soil was inhaled, internal compaction could represent a subtle, yet viable clue, of a post-depositional struggle to escape the grave.

To date, there has been no forensic archaeological research in the area of internal compaction. Experiments are pending the development of a device which can replicate body movement within a backfilled grave. Excavation strategies in situations where live burial is a consideration should include the creation and maintenance of profiles at planes perpendicular to the plane of expected movement. For example, one would expect an individual buried alive to push with the feet in an effort to free himself. The excavator should therefore consider establishing a profile perpendicular to the direction of the pushing action of the victim's feet in order to document the compressed fill beneath and around the heel. Conclusion

As archaeologists tasked with assisting law enforcement in reconstructing events surrounding a crime scene we too often yield to pressure or acquire tunnel vision and focus only on the removal of the body and immediately associated pieces of evidence. In forensically significant settings, the ability to document not only the position of evidence but the means by which it got to a given position is paramount. Equally as important is a realization that evidence such as tool marks, internal compaction, and subsurface sedimentation and cracking, survive burial and can be recovered through careful excavation. Understanding geotaphonomy through the full application of scientifically based archaeological procedures insures the crime scene processor can realize the potential for such typically overlooked evidence. In summary, Geotaphonomy can potentially offer the crime scene investigator the following:

1) An understanding of the nature, position, and chronology of events associated with the pit and its contents;

2) Indications of the number of suspects as well as their tools and techniques;

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3) Evidence of the actual, or attempted, removal or addition of evidence;

4) Indications of criminal planning and intent reflected in characteristics of the disposal features; and

5) Corroberation or contradiction of eyewitness testimony.

References Haglund, William D. and Marcella H. Sorg (editors) 1997 Forensic Taphonomy: The Postmortem Fate of Human Remains, CRC

Press, Boca Raton, FL. 2002 Advances in Forensic Taphonomy: Method, Theory, and Archaeological

Perspectives, CRC Press, Boca Raton, FL. Hochrein, Michael J. 1997a Buried Crime Scene Evidence: The Application of Geotaphonomy in

Forensic Archaeology. in Forensic Dentistry, Paul Stimson and Curtis Mertz, editors, CRC Press Incorporated, Boca Raton, FL. pp. 83-99.

1997b The Dirty Dozen: The Recognition and Collection of Toolmarks in the Forensic

Geotaphonomic Record. Journal of Forensic Identification , 47(2): 171-198.

2000 Beyond the Grave: Applied Archaeology for the Forensic Sciences. A

Paper Presented at the 52nd Annual Meeting of the American Academy of Forensic Sciences, 2000, February 21-26, Reno, Nevada.

2002a An Autopsy of the Grave: Recognizing, Collecting, and Preserving

Forensic Geotaphonomic Evidence. In W. Haglund and M. Sorg, editors, Advances in Forensic Taphonomy: Method, Theory, and Archaeological Perspectives, CRC Press, Boca Raton, FL. pp.45-70.

2002b A Bibliography Related to Geotaphonomic and Forensic Archaeological

Field Techniques. United States Department of Justice, Federal Bureau of Investigation, St. Louis Division, St. Louis, Missouri.

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Wilson, Wayne 1994 Was the Boardinghouse Body Buried Alive? New Book Offers Horrifying

Theory on One of Seven Deaths in Sacramento. The San Francisco Examiner, March 12, 1994, Saturday, Fourth Edition, p. A-4.

Wood, William P. 1994 The Bone Garden, The Sacramento Boardinghouse Murders. Pocket

Books, New York, NY.