Manual evaluation (and other methods)

If the area of investigation can be narrowed down to a relatively small area, the use of invasive techniques becomes justifiable. Augers and ground probes can sometimes be used, but both need to be deployed systematically within a grid system. The latter tests (somewhat subjectively) the firmness of the buried soils or the depth of bedrock, and the former draws a narrow vertical column of soil in order to assess the likelihood of disturbance (see case 12). Both can be effective, but both are of very limited value in untrained hands and in difficult or stoney sub-soils. A more useful primary invasive technique, and the one which presents minimum loss of evidence, is that of the cadaver dog (e.g. Rebmann et al. 2000). These dogs are able to detect the gaseous by-products of decomposition of human remains and are either trained on appropriate human materials (e.g. teeth, blood or clothing containing decompositional products), or on materials which have similar properties, notably pig remains. Some trainers use chemical concoctions (pseudo-scent) which simulate actual body decomposition scents, although

opinions differ as to the effectiveness of this. In searching for individual graves, there is arguably some dependence on appropriate wind strength, as well as on temperature and humidity, and some research work has taken place (e.g. Komar 1999). However, the application to mass graves seems undervalued, despite the fact that the scent source can be considerably enhanced although in some waterlogged contexts decomposition processes are not ‘normal’ and can in any case be arrested, and may not produce recognisable gaseous by-products – this needs researching as the potential for success is arguably greater. Dogs also have a value in identifying those locations where bodies have been dumped before being moved elsewhere and buried. Depending on training school, dogs are able to distinguish between animal and human carcass elements in both surface and buried environments, although those in the USA tend to be trained on air-scent only. In the latter, the ground needs to be ‘vented’ before the dog is brought in to play. This involves probing the ground to as deep a depth as possible, usually to around 1m, using a probing device which leaves an airway at least 1cm in diameter through the ground for the release of decomposition gasses. Venting carried out using an auger or similar device also has the potential to identify disturbed earth.

Some handlers prefer to pepper the ground with a large number of randomly placed vent holes within an area of approximately 2
2m at the target area. Other may use a line approach, and place a line of vent holes spaced regularly at 0.5m intervals across a target. Both methods work on the basis that any buried remains will release gasses through the vent holes and enhance the dog’s ability to detect buried human remains.

The dog is brought to each hole in turn, usually downwind and holes are searched in the same order as they were made. This is to negate the possibility of a dog ‘winding’

a contaminated hole made by a dirty probe and jumping across the hole containing the scent source, thus giving ‘false’ indications. The dog’s response is judged accordingly.

In the same way that geophysical survey requires a skilled interpreter, the responses of cadaver dogs also need a skilled and experienced handler, necessary not only for bringing the dog into detection mode, but also in being able to judge the level of the dog’s response as it reaches each vent hole. Sometimes body dogs can be confused by other scents which might either mask the smell of human remains or contain elements of human remains scents (e.g. methane) but which originate from different sources, such as in peatlands. Dogs are not contextually aware; they merely respond to the scents they have been trained to detect. Furthermore, if a dog responds to a particular vent hole, or series of holes, this does not necessarily indicate that the source lies directly below.

The gasses to which the dog is reacting may be released through the vent, but the source may lie uphill or in a different part of the hydrological regime which has brought the scent to that particular vent hole. It then becomes the role of the handler to source the remains more precisely using further carefully positioned vents. The movement of scents in such scenarios can be likened to the path taken by smoke from a flare if released inside a dry stone wall, i.e. the path of least resistance.

Dogs are ideally used in combination with other techniques, depending on the importance of the location within an enquiry. In many circumstances, when a specific location has been identified as being potentially suspicious (for example, a back garden), the ground surface can be evaluated and geophysical survey implemented (e.g. cases 4 and 6). Any anomalies identified by the geophysics can then be tested by the dog through the normal venting procedure (Figure 2.5). If the surfaces are dense and GPR has been used, vents can be facilitated using power drills and the dog subsequently

Figure 2.5 Top: using drills to vent solid surfaces for the body dog.

Bottom: removal of upper soils can indicate disturbances cut into undisturbed deposits

Source: courtesy of Greater Manchester Police.

brought to each vent in the normal manner. A response by the dog would then neces-sitate more extreme, but controlled, intervention. If the dog fails to respond to any of the anomalies, then the next stage in the search process will requires the SIO to make a key decision. If the search has been one brought about by generally unfounded allegation or the need to eliminate the garden from an inquiry, then the search may be concluded at that stage. However, if the SIO has strong information in the significance of the garden, he or she may wish to pursue the search effort and input more resources into investigating the garden. This is a management decision and one which must be respected by archaeologists even if they are fully convinced that there are no burials present (but see case 3).

If investigation is to continue, the next stage may involve stripping the topsoil down to undisturbed deposits, usually to bedrock or other undisturbed horizons (e.g., clay, gravel or similar), or even to anthropogenic levels which are known to predate the incident in question. The key factor is to ensure that the horizon is one into which the disturbances caused by burial are readily visible. This is best and most rapidly carried out using a machine, although there are often circumstances of access, or gardens of relatively small size, where this is not always possible, or where there is a clear level of stratigraphy present (e.g. cases 2, 3 and 5). In these cases the topsoil can be removed by hand, most effectively by clearing a 1m wide strip of undisturbed subsurface across one end of the garden by horizontal spading. After this has been exposed and cleaned by trowel it can be covered by the spoil from the next 1m strip, and so on until the whole garden has been systematically stripped, cleaned and covered over again. The method ensures comprehensive coverage and negates the cost of removing spoil on site.

On larger sites, the most efficient type of machine is one which can revolve 360° on tracks and offers the facility of a wide, toothless, ditching bucket usually 1m wide (teeth tend to create soil and possible body damage) to scrape away the upper soil horizons.

The effectiveness of the process depends entirely on the ability of the machine driver to work carefully and horizontally removing only a few centimetres at a time, and on the archaeologist being able to provide the correct instructions and maintain a thorough watching brief. As with manual clearing, the logistics of the process need to be thought out well in advance. In some instances the spoil will need to be moved off site completely and returned later, in others it will be possible to move the spoil systematically around the site to follow the machine. Either way the machine routing has to be arranged to minimise surface damage. The most efficient way is to clear a corner of the garden to bedrock, trowel it across, and then locate the machine there for systematic movement on to each fresh area as it becomes exposed and eliminated.

When the upper strata have been removed, anomalous features can be quickly cleaned with a trowel and examined, usually by half-section (Figure 2.5; also Chapter 4).

In some geological or domestic environments features or intrusions are not always clear-cut and may be blurred by alluvial, root, or even rodent action. Usually there a number of features to be investigated, and there is simply not time to treat each one in painstaking detail. The most practical method implicitly assumes that the feature is there to be tested to determine whether it is a grave or not, rather than to assume a grave in the first instance. The process may lack a degree of archaeological purity, but is a rapid and effective way of eliminating features by using archaeological principles.

Features need not be ‘grave-sized’ or ‘grave-shaped’ as victims may be dismembered and body parts buried individually. Neonate and infant victims, however, pose their

own problems in that any disturbance is likely to be small and difficult to pick up.

However, the smallest burial is unlikely to have sides less than about 20cm (i.e. the width of a typical spade).

If the disturbances are too large to half-section, clarification can normally be made by positioning narrow evaluation trenches across the suspect areas. These trenches can be as narrow as 30–40cm, positioned across the main part of the feature, and can be excavated rapidly until undisturbed soils are reached and the character of the disturbance identified. However, once invasive testing techniques are deployed, there is always a compromise between finding the remains and preserving the full integrity of the evidence. Nevertheless, even relatively deep features can be tested quickly, either by following layers and separating the spoil, or by following ‘spits’ of convenient depth.

In most instances the features will be innocent and can be rapidly eliminated, but they are still potential crime scenes and need to be recorded by note and measured drawing by the archaeologist as part of a brief report. The location may need to be returned to and the notes, no matter how trivial, will be one of the few records of the event maintained in the incident file. They may also be disclosable.

If, through either half-section or trial trench, the features are identified as a grave, then a full archaeological methodology will need to be employed (see Chapter 4) and the location will move into the status of a crime scene. This is the time at which some SIOs may (annoyingly) see no further need for the archaeologist given that the object of the search has been achieved. However, there are now key points of evidential integrity at stake and these illustrate the difficulty of making a hard and fast distinction between the processes of search and recovery respectively. The search process has now identified part of the edges of the grave and, in all probability, has outlined the full extent of the area of evidence potential. Furthermore, the exposed section will show how the grave was filled in, it will also guide the excavators in how to remove the remainder of the fill, and the retained excavated layers or spits will show the material used for infilling. The condition of the human remains will be apparent and further action can be informed accordingly (see Chapter 4, case 19). In short, the search process so far will not only have provided key data about the burial and given guidance as to recovery, but will also have done so with minimal loss of evidence.

A similar approach can be adopted on occasions when it becomes necessary to test targets identified from the air. Police forces have access to skilled military aerial investigators through the Joint Air Reconnaissance Intelligence Centre (JARIC) which is able, at short notice, to take aerial photographs of suspect areas and recommend appropriate points of likely vegetation change or soil disturbance. Once located on the ground, these can then be investigated by either a dog, by using narrow test trenches, or both. A difficulty here is that an experienced aerial observer is likely to be able to identify a number of possible targets even in places which are probably implausible, for example, in an open front garden, or in the middle of a field. As with geophysical anomalies, these will still need to be tested if total elimination is to be ensured. The SIO is effectively committed to this when the decision to use these techniques is made.