Archaeology

Background

Forensic archeology first emerged in the later 1970s as part of a broader recognition of the role of physical anthropology in medicolegal matters. In Britain where archeology was traditionally seen as a freestanding discipline with roots embedded more strongly in excavation and field skills rather than in the study of human skeletal remains, forensic archeology developed somewhat later. Furthermore, differences in medicolegal practice at scenes of crime between the two countries also serve to confine the role of forensic archeology in Britain to one more specifically concerned with field activities than with postmortem study. Elsewhere forensic archeology plays a less prominent role in criminal investigation, although with formal interest now developing in other parts of northern Europe, South Africa and Australasia. Additionally, the excavation of mass civil or war graves in places such as Argentina, Ruanda and Bosnia have widened the application of archaeological recovery techniques to other parts of the world.
Archeological input to criminal investigation reflects the skill base of modern archeology and its role in society. In Europe and North America arche-ologists are nowextensively employed on behalf of central and regional government in order to identify and assess archeological remains ahead of planning and redevelopment schemes. The archeologist’s interest is almost exclusively concerned with understanding about the past from buried material remains; this can be expressed in general terms of finding evidence, recovering evidence in a manner which will maximize its value, and in interrogating evidence in order to reconstruct sequences of past events. As a process this has much in common with law enforcement detection and is nowwidely recognized as having a role in modern forensic investigation when buried remains are encountered. This skill base provides a collective expertise in landscape analysis, knowledge of resources (photographic and cartographic), geology, land use, site location methods and excavation techniques.
In addition, archeology is a process which has access to a range of associated areas of specialties many of which also have forensic application. These include, for example, aerial photographic interpretation, the identification of pollen assemblages, soil analysis, animal/human bone differentiation, and the recognition of cremated human materials. Archeolo-gists have also developed techniques which are peculiarly suited to forensic purposes, for example geophysical survey for the detection of shallow subsurface remains. Archeology, like forensic science, is also concerned with scientific analysis across a broad range of material types.
The main areas of interest common to both archeology and criminal investigation might be listed thus:
• Skeletal analysis (physical anthropology)
• Scientific analysis
• Field search
• Excavation and recovery
The first two of these are discussed more fully elsewhere in this volume and are not detailed here other than for crossreference purposes. Skeletal analysis, for example, is a major section in its own right with a recognized modern history in criminal matters as well as in military and disaster scenarios in the United States. Equally, the application of both physical and life sciences is now a fundamental part of modern archaeology and much analytical science is dedicated to matters of provenance or dating. Provenance – the ascribing of a finished product (e.g. pottery) to the location of a natural source (e.g. of clay) -is a well-attested method of evaluating the trade, transport and social economics of earlier societies. Like forensic science and the Locard principle, it ascribes a material to a parent source. The methods used are also common to forensic science, as indeed are many of the materials under study (e.g. silicates, soils, metals, pigments etc.). There are many crossreference points throughout this volume although interplay between the two disciplines of forensic science and archeological science respectively is curiously exclusive.
Absolute dating methods also have some relevance here. Although archeological and forensic time-scales have little in common, radiocarbon dating has some application in demonstrating whether human remains pre- or postdate 1952 (the era of atomic weapon testing which generated high atmospheric radiation levels). This is particularly important in providing coarse dating in instances of stray or displaced human bone. More relevant perhaps is the observation of taphomomic (decay) processes in buried environments and the determination of interval since deposition. There is a growing area of interest in both human and associated modern materials buried over short time-scales.
The number of homicide victims who are ultimately buried to avoid detection is relatively small, perhaps little more than 2% of the total victims, although several of these have been multiple or serial killings and have been of high profile. A greater percentage involves concealment in one form or another. Recent history has emphasized a number of cases which have demonstrated a potential role for archaeology: in the United States these have been highlighted by one of the pioneers of forensic archaeology, Dan Morse, from cases in Florida, Illinois and Texas, and in Britain notably from the Moors Murder enquiry in the early 1960s and the later investigation of the north London garden of Dennis Nilsen in 1984. All these situations were effectively archaeological scenarios which would have been approached and handled in very different ways if taken on a straight archeological basis. However, since the late 1980s, but with some notable setbacks, such cases have been fewer and awareness of the potential value of using archeologi-cal techniques has increased among law-enforcement agencies. It is, nonetheless, not simply a straightforward matter of creating awareness or of applying appropriate techniques. The process is two-way: archaeologists also need to recognize the protocols and processes of crime scene work, the time-scales involved and, most importantly, the judicial constraints which surround forensic work. The philosophy and practise of forensic archaeology is very different from that of its parent. Also different are the objectives and the means to achieving those objectives (see below).
Archeology is based on the principles of stratigraphy, namely that the ground subsurface comprises discrete layers of earth which differ in texture, color and physical properties reflecting the effects of both natural and human activity over time. These layers can be generated by natural processes of soil formation or, in areas of habitation, by building, farming and general development caused by a wide range of activities. In rural areas these layers can be of relatively shallow depth above bedrock (i.e. a few centimeters), or in urban areas up to several meters deep reflecting centuries of activity and use. Archeologists try and interpret what each layer represented in past time, and also how the various layers relate to each other chronologically. The order of their formation can usually be determined quite easily. Many modern layers, particularly those relating to building activity, may be able to be dated by modern records.
In effect, the profile of layers in a given area of the subsurface makes a type of statement about the history of that place. It also presents a ‘snapshot’ in time, in that all the layers have a broad chronological relationship in which one layer which overlies another is clearly of later date (Fig. 1). If a grave is dug into the ground the existing layers in that place become disturbed, a relationship occurs between these layers and the grave, and the time-frame of the overall stratigraphy becomes extended. Archeology involves identifying and interpreting changes of this type.
Example of local stratigraphy showing development of layers through time, including imposition of wall (right) and later pit or grave (top left). Drawing by H Buglass.
Figure 1 Example of local stratigraphy showing development of layers through time, including imposition of wall (right) and later pit or grave (top left). Drawing by H Buglass.
A grave identified within these layers will have a contextual integrity, no matter how few layers are involved. Recovering or excavating a victim without awareness of related layers (i.e. the layers which are earlier than the grave, the layers which are later than the grave, and the grave itself) will stand to lose much of the evidence that may be available. Questions which the pathologist or medical examiner will try to answer pertaining to interval since death, identity, or the cause/manner of death may be more readily resolved if the edge and sides of the grave can be defined in three dimensions; this effectively identifies the physical boundaries within which the human remains and associated materials will be found. The presence of the associated layers may assist in dating the event.
Human remains often appear during building or development work when bones become unearthed during machine excavation. In such instances it is particularly important that remains are retained in situ in order that the relationship of the grave within its buried environment can be retained as much as possible.


Search

Locating buried materials can involve a range of target types, although the most common are human remains. Other targets can include firearms, drugs or stolen goods covering all shapes, sizes and materials of organic, inorganic, ferrous or nonferrous type. In nearly all instances the method of search involves the identification of the disturbance caused by the burial in the first instance, rather than the item buried. Even with homicide victims (for which this entry is primarily intended) the target characteristics can vary according to stature, age, clothing or dismemberment.
The initial phase of search usually involves targeting the most likely locations in a given area using factors of feasibility (i.e. geological suitability, soil cover, land use etc.) in combination with a suspect’s movement, psychological profiling and other intelligence. ‘Dump-site’ analysis as it is known, has been the subject of valuable research in both Britain and the United States: it enables factors such as the relationship between victim and suspect; location of last sighting, or likely distance traveled, to be fed into the search equation. The use of geological maps, existing aerial photographs (vertical and oblique) can facilitate this. Often the process can be carried out as a ‘desktop’ study and the target areas located accordingly. This is highly desirable as it does not arouse suspicion, run the risk of damaging evidence on the ground, or necessarily incur great expense.
Once the area can be narrowed down, a more detailed approach can be taken. When a victim, or for that matter any object, is buried, the subsurface is disturbed in relation to the surrounding environment. This disturbance can have a number of effects on (a) the subsequent ground vegetation, (b) the immediate topography, and (c) the geophysical signature of the disturbed area.
The original digging of a grave is likely to create a looser, damper, more aerobic area of ground when the grave is filled in. This will almost certainly affect the height or density (or even species) of the resulting vegetation on the ground surface (Fig. 2) – an effect that may become more pronounced as the human decay process provides nutrients to an already moister soil medium. The converse might apply if the grave was filled in with stones and the vegetational growth inhibited accordingly. These changes will have a long-term effect. There will also be a shorter term effect on the where the excavated spoil was dumped when the grave was first dug. There may also be excess soil providing a low mound over the grave which in time may sink to form a depression as the grave infill consolidates. A secondary depression may occur as the body cavity collapses, and cracking may take place at the grave edges during dry weather. Additionally, the infilling of the grave may contain obvious traces of deep disturbance such as soil or bedrock of different color (e.g. clay or chalk) brought to the surface in an otherwise undisturbed area.surrounding ground surface
Some potential effects of burial on surface vegetation.

Figure 2 Some potential effects of burial on surface vegetation.

Although many of these features of vegetational, topographic or soil change might be seen at ground level, they are often at their optimum when viewed from the air, some features being particularly prominent through the use of shadows at appropriate times of the day. Aerial reconnaissance is an ideal nonin-trusive primary method of search, but its effectiveness may be seasonally specific given that light and land use are variable components. Any photography, however, may be supported by imagery analysis for which there is now highly developed military expertise.
There are a number of methods which can be used to detect buried remains; some of the most commonly used are listed below on a scale which runs from the noninvasive (i.e. those least likely to destroy buried evidence) to the invasive (i.e. those most likely to destroy buried evidence). The list is not comprehensive and is presented only as a general guide; it also tends to reflect the selective narrowing down of the target area. The deployment of these techniques, and their use in sequence (which is strongly advised), depends on a range of factors including the local environment, the geology, the nature of the target, and the interval since burial. Some techniques, particularly geophysical methods, are only suited to certain types of environment or situation (e.g. indoors, outdoors, concrete, soil, clay, etc.) and are wholly ineffective in other environments. It is not possible to outline the complex range of variables in the space available here; search is a specialist area of expertise for which advice should be sought (see below). The primary use of one method may completely negate the effectiveness of another, or may be wholly wasteful of resources. A routine list of techniques might be as follows.
• Aerial photography and reconnaissance for the detection of disturbances identified from the vegetation or topography (shadow or color change) or by soil marks (color).
• Field craft for the detection of discrete areas of vegetational, topographic or soil difference, also for the presence of ground cracking and for the identification of burial locations by using prominent local landmarks or features which may have been used as guide points by the offender (sometimes known as ‘winthroping’).
• Body-scent dogs for the identification of buried remains by virtue of characteristic odor which may be released from the ground by systematic or selective probing.
• Geophysical survey for the detection of shallow subsurface features, typically by using electrical resistance (to detect disturbance which has affected local moisture content of soils), magnetometry (to detect disturbance caused by changes to a local magnetic field), ground penetrating radar (to detect responses to changes in ground density using an electromagnetic pulse) and metal detector (to detect both ferrous and nonferrous items associated with a buried individual).
• Probing/sampling for the identification of subsurface disturbance, emission of methane, or thermal change.
• Excavation for the identification of soil disturbance (color, texture and physical properties), and changes consistent with a grave (see above).
The effectiveness of each of these methods depends on a range of factors, not least of which is the ability to detect a disturbance or change within an otherwise undisturbed environment. Also to be considered are effects brought about by the decay process of the body itself. This may not only generate heat (and allow the target to be identified using thermal imaging during the decay activity) but it may also affect the geophysical properties of the grave and inhibit or enhance the likelihood of detection depending on the survey technique used. Variables which might accelerate or delay this decay process include factors of depth, climate, soil pH, wrapping or clothing, water content and presence of oxygen. Optimum methods of search rely on knowledge of as many of these variables as possible.
In Britain a central search advice facility is available under the auspices of the Forensic Search Advisory Group. The group consists of specialists who adhere to a code of practice and who have experience in the search and recovery of buried remains. In the United States the group NecroSearch operates a similar, larger, facility based in the Colorado area. Both groups operate a number of associated research programs on decay and detection and maintain test sites.

Recovery

Although recovering buried remains can occur in a variety of different situations and environments the process of recovery follows a well-established routine in order to maximize the evidence available. This is based on the awareness that archaeology is a destructive process and that each recovery operation is seen as a nonrepeatable exercise.
When the burial of a victim takes place, three main activities are undertaken: the physical removal of earth from the ground; the deposition of the body in the grave; and the infilling of the grave. Proper forensic investigation of the grave follows this process in reverse order: the grave deposits are removed to see how the grave was in filled; the body is exposed in order to show the manner in which it was disposed; the body is lifted; and subsequently the manner in which the grave was dug is identified.
Once the outline of a disturbance has been identified it is normally half-sectioned (i.e. half of the infill should be excavated), usually by bisecting the long axis at around the midway point leaving an exposed vertical profile of the unexcavated part of the disturbance. This has two main benefits: first, it serves to identify whether the disturbance is in fact a grave or not without excavating (and destroying) the whole disturbance, and secondly, it provides visible evidence in the exposed profile as to how the disturbance was infilled, and how it might most effectively be excavated to resolve questions pertinent to the particular case.
Sometimes, because of depth or other constraints it becomes necessary to extend the working area available by excavating additional space adjacent to the grave itself (having first suitably recorded the grave sides). This allows lateral access to the grave/body and facilitates proper excavation. In situations where this is impossible, it may be necessary to construct struts or planking to wedge across the grave as a working platform. This ensures that the weight of the excavator is taken by the planking rather than the underlying victim (at whatever depth), thus minimizing unnecessary damage to the victim and to any associated materials. Although no two scenes are ever the same, and each has a different situation and time-scale, a number of general elements need to be addressed during the recovery process. These are outlined below and should be seen in general terms only, given the great variability of situations and constraints of individual scenes.
Preserving the integrity of the grave It is critical that the integrity of the grave (i.e. the boundaries and area of disturbance) is maintained throughout, in order to preserve the exact situation that occurred when the victim was buried. This not only allows the original scene of crime to be recreated, it also insures the absolute recovery of the individual and any associated materials. Furthermore, determination of the parameters of the grave is also necessary in order to eliminate the possibility of contamination.
Emptying the grave The grave infill is normally removed by trowel in layers which reflect the manner in which the grave was infilled by the perpetrator. This also enables the nature of the grave infill to be identified. If there are no observable layers, the grave infill is excavated in a series of ‘spits’ typically 10 cm deep in order to provide a controlled removal of the grave deposits.
Objects found within the grave Exhibits discovered within the grave are normally recorded in three dimensions within the layers or ‘spits’ in which they occur. Recording of this type is now standard practice on archaeological sites and is carried out using an electronic distance measurer (EDM) which is both accurate and rapid. This ensures that individual objects are properly associated with any layers in which they occurred, and that the contents of the grave can be recreated spatially. These exhibits can include items belonging to the individual and his/her clothes, such as buttons, jewellery and the contents of pockets, or items associated with the burial event such as a weapon, papers, clothing and wrapping, or material introduced to the grave infill in an attempt to minimize discovery, such as rubble or lengths of wood.
Recording Because archeology is a destructive exercise the recording process is comprehensive, and wherever possible is undertaken in three dimensions. The outline of the grave is normally planned with reference to permanent base points at ground level in order that it can be relocated in the future; the base and the profile of the grave are planned using graphic conventions such as contours or hachures, and a vertical record of the infill from the half section (above; Fig. 3). This section is drawn as part of the basic recording methodology and is essential in demonstrating the dimensional properties of the grave.
On archeological sites human skeletal remains are drawn to scale as part of the recording process; this may not be possible at a scene of crime, but the disposition of the body and the location of any associated features are usually subject to detailed photographic record. The body is normally revealed in its entirety before lifting. The lifting process itself is a delicate operation which takes place bearing in mind that footprints may have survived in the floor of the grave. The method of lifting varies depending on factors of depth, condition and wrapping, but is often most satisfactorily carried out by sliding a board or metal sheet under the body, although this may have implications for the survival of any foot impressions.
 vertical profile of grave infill taken at approximate half-way point across disturbance. Right: hachure plan of overall grave profile on completion of excavation and removal of victim. Cross-reference provided by section line
Figure 3 Left: vertical profile of grave infill taken at approximate half-way point across disturbance. Right: hachure plan of overall grave profile on completion of excavation and removal of victim. Cross-reference provided by section line
Photography occurs throughout the recovery process, ideally taken from a fixed point at one end of the grave (normally the foot end) and identifies specific rather than arbitary points during the recovery process, for example before excavation, at changes in layers or ‘spits’ in the grave infill, at the point where significant exhibits occur, when the body is exposed, and when the body has been lifted. These photographs will not only record the main sequences of events but, viewed in reverse order, will recreate the offense in exactly the way it occurred.
Excavation and recording along these lines may be able to answer several important questions about the original crime.
• How was the grave dug and with what implement? This may be resolved by examination of the sides of the grave which exhibit mechanical grab marks, shovel (curved edge), spade (straight edge) or pick (short blade) markings. In exceptional instances it may be possible to identify a specific implement which bears characteristic markings or nicks on the blade. This is especially the case in soils which sustain impressions such as heavy clays.
• Was the grave dug in a hurry or was it carried out carefully in a prepared way? The professional opinion of the archaeologist may be canvassed in an attempt to determine whether a grave site was premeditated, on the basis of its profile and depth (or even of its primary silted deposits if the grave had been open for some time before burial). This clearly has implications for manslaughter or murder charges.
• Did the grave contain any evidence of cause or manner of death? The infill of the grave may bear traces of toxins, blood or firearms discharge and the excavator will be prepared for these within the grave deposits. Toxins will normally be the subject of a sampling strategy by scene-of-crime personnel. The location of bullets/pellets may be determined by the use of a metal detector. Bullets may, for example, have passed through the base of the grave into the subsoils if the victim was shot in the grave itself.
• Was there transfer of material from offender to grave infill? Locard’s principle points to the natural transfer of material (e.g. fibers, hair, sweat or footwear impressions) into the grave infill. These are often extremely hard to identify or recover, but should be borne in mind during the recovery operation.
• Was there foreign material in the infill or layer matrices, and if so where did it come from? During the excavation the descriptions of individual layers or ‘spits’ are recorded using accepted soil definitions and terminology. Soils or materials which are unlikely to have been dug out from the area of the grave can provide additional evidence. Their provenance may have considerable bearing on convicting the offender.

Conclusion

Forensic archeology is now an acknowledged area of expertise in field search and recovery and has been legally recognized in prosecution and defense arenas during the late 1980s and 1990s in both the United States and Britain, as well as being actively developed in other European countries. It has been recognized as a subdiscipline in its own right and is offered within university degree programs on both sides of the Atlantic. Forensic archeology also features in post-experience and validated postgraduate courses and seminars intended for both archeologists and law enforcement personnel, forensic scientists and associated professionials. Despite its academic origins, its familiarity within sampling, three-dimensional study and recording processes lends itself naturally to scene-of-crime investigation. Furthermore, its extensive repertoire of associated disciplines provides a valuable range of distinctive forensic skills.

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