Case studies 14–29
4.4 Identifying evidence
Before excavation proceeds it is important to remember the processes that took place in creating the grave – the digging, the deposition, and the infilling respectively – and applying a reverse of that process in the recovery exercise. Critical in the excavation process is maintaining the integrity of the grave; this necessitates that during excavation, where practically possible, every care must be taken to ensure that the sides of the grave right down to the base are revealed and maintained. Failure to ensure this lays the
process open to accusations of contamination from surrounding layers that may be earlier or later than the grave itself, or of inefficient collection of evidence, especially directly above the base of the grave below the body where items such as buttons, coins, or even projectiles can collect when the body decomposes (see case 21). The grave as a feature will hold such clues as the mode of digging, the tools used and the direction of digging (Hochrein 2002). The grave cut itself, the fill, and evidence on and around the body will potentially hold the majority of the evidence available to an enquiry, particularly when the grave is a serendipitous find and there is no criminal context for the burial. Conversely, if the grave is the result of a concerted search effort, the missing person will be known, there may be a suspect, and the timeframe of dis-appearance will already have been recorded. In the former, there is always a danger of making assumptions and hence of not being entirely objective (e.g. case 22). Either way, the potential of the available evidence within the grave will only be realised if excavation is conducted by appropriately experienced experts. The buried evidence will be interrogated and the following questions, while not exhaustive, are typical of those which will need to be addressed:
• How was the grave dug and with what implements?
Digging a grave can be undertaken using a variety of different implements, ranging in size from a machine with a bucket or front loader, down to a small collapsible military-style trenching spade. Depending on soils and substrates these can leave characteristic tool marks or patterns in the grave-sides. Detecting and excavating machine teeth marks represents a standard feature of mass grave work (see Chapter 5, Section 5.5.3; Figure 4.5) but marks of smaller implements are usually harder to detect even in compacted deposits such as chalk or clay. Nevertheless, it is often possible to distinguish between the use of a spade, a shovel, and a garden fork and this itself may be an important piece of evidence. Most implements exhibit characteristic wear marks and are potentially identifiable (e.g. Humphrey and Hutchinson 2001), although little research has been carried out on the wear patterning of garden tools (but see Hochrein 1997, 2002).
• Was the grave dug in a hurry or was it carefully prepared?
This ostensibly simple question is heavily loaded as it implies that (at one extreme) a shallow irregular grave was dug in haste, whereas (at the other extreme), a deep grave with clean sides was carefully prepared in advance. Taken further, the implication is that the former reflects an unpremeditated act (manslaughter), whereas the latter assumes a premeditated act (murder). Archaeological opinion can only be restricted to commenting on the speed with which the grave in question might be dug, not to the implications of that speed. Those are for the barristers.
It is, however, important in advance discussion with barristers, that the archae-ologist makes clear the limitations of opinion. There are other reasons why graves may be shallow (tree roots, laziness, water table, etc.), and there are equally reasons why they might be deep (softness of substrates, avoidance of scavengers, etc.). In one instance where the offender was a professional hole-digger (case 23), the burial was probably carried out in haste, but to a depth of over 2 metres with almost sheer sides.
• Is there evidence of the grave being left open before burial of the body?
Recognition of a grave which has been left open before burial is probably the only way to indicate a premeditated act, and is difficult to prove. The main pointers can include the presence of silted deposits in the grave base, accumulation of blown material such as leaves, twigs, etc. in the bottom, and weathered grave-sides (see also Hochrein 2002). Silted deposits, however, may be impossible to identify unless carefully excavated and will become completely unrecognisable once body fluids have been released and the soil biochemistry has been altered. Leaves and twigs can be argued to have fallen as part of the action of depositing the body, and weathered edges are extremely difficult to define objectively. Difficulties of this nature were encountered in a case where a victim had been seemingly buried in the ground but had been discovered trussed up on the ground surface adjacent to the grave (case 17).
• Is there evidence of post-mortem interval?
This effectively assumes that the time of death and the time of burial are largely synchronous. A fresh disturbance, a spread of spoil in the vicinity, and surface trample can point towards a very recent deposition, but in most instances there is little or no visual surface evidence. Excavation, however, may be able to provide Figure 4.5 The excavated machine tooth marks from a mass grave
a terminus post quem or a terminus ante quem for the burial from material located within the grave itself and from layers around and above the grave (see case 24), although this may necessitate excavation wider than the grave itself. Many modern items contain dating evidence, either from batch numbers, ‘sell by’ dates, wrapper styles, etc. Material is often thrown into the grave as a useful dumping site during burial and this has been known to include pages from magazines and newspapers.
Many non-archaeologists (e.g. a jury) find these termini confusing and it is as well to rehearse a simplified explanation before any court appearance. Alternatively, there may be good stratigraphic evidence to indicate that the grave is cut through, or is sealed by, layers which can be related to specific events, for example, building activity or land use. The use of section plans, or even measured drawings are essential if this line is followed.
Tree or plant roots may also be of some value if they demonstrate having been severed during the digging of the grave, or if they are seen to penetrate the remains (Willey and Heilman 1987). This is a specialist area of expertise, as is interpreta-tion of the vegetainterpreta-tion on the grave surface, but is one which the archaeologist should be able to recognise, record and sample for specialist input as routine. On a broader front, it may be possible to determine season of burial through presence of plant macrofossils, pollens, spores or leaves compressed and sealed within the grave fill. In fact, they may indicate an ecological profile of the murder scene which may be different to that of the burial. Less helpful, however, is taphonomic evidence (but see also Hopkins et al. 2000). Rates of decay can vary very signi-ficantly reflecting a combination of extrinsic variables (e.g. depth, clothing, climate, wetness, soil environment, etc.) and intrinsic variables (e.g. age, sex, health status, diet, genetics presence of gut flora, etc.). All these can act singly or in combination and consequently this subject is far from being an exact science (e.g. Haglund and Sorg 1997, 2002).
• Is it a burial, and, if so, is it criminal or archaeological?
In the case of accidentally discovered remains, these are questions which almost everyone at the scene will ask, but which only the archaeologist is likely to be able to answer, if indirectly. There is a substantial archaeological difference between remains which have been deliberately buried and those which have become buried through natural processes (see Chapter 1, Section 1.4.3; Figure 1.5) and which may not have a criminal origin (e.g. case 25). It will be the role of the archaeologist to establish whether a grave cut exists or not, and whether any ‘disposal’ was originally on the ground surface. This issue is mostly restricted to articulated remains and can be resolved by careful excavation of any overlying soils and materials. A botanist may often have an important role to play here in analysing both surface remains and those which may underlie the body. In cases of dis-articulated or scattered remains (e.g. case 26) it may be harder to identify any original grave site (for possible analysis see Morse 1983: Table 6.1; Haglund et al.
1989).
By maintaining the integrity of any grave edges and base, it may be possible to show that the burial occurred within a timeframe which is not modern and which, for the purposes of police enquiry, occurred more than approximately 70 years ago. Remains discovered before this (arbitary) date are considered not worthy
of investigation on the assumption that any perpetrator is unlikely to be still living.
However arguable this premise might be, there needs to be a line drawn somewhere.
In the absence of such features as modern dental restorations or other protheses, stratigraphic evidence is likely to be the best absolute method of differentiating between forensic and archaeological contexts (e.g. case 27), but in the absence of any useful buried context, other evidence needs to be forthcoming. Archaeologists familiar with period cultures will also be familiar with specific burial configurations (e.g. crouched burials) although these too can be forensic, the nature of associated grave furnishings such as weapons or personal adornment, or burial features which may leave characteristic traces even when ploughed out, such as mounds or cairns (see case 29). On rare occasions when none of these evidence types are forthcoming, for example, in the case of some bog burials (e.g. Brothwell and Gill-Robertson 2002), other criteria need to be employed. The most obvious of these is to employ absolute dating methods although this presents a major challenge within the required modern timeframe. However, radiocarbon dating has the advantage of being able to distinguish between deaths occurring before around 1955 and those occurring after 1955 owing to the amount of weapon radiation present in the atmosphere (Ubelaker 2001). This is a part solution to the problem only and is useful, for example, in eliminating ‘ancient’ human material unearthed during building operations. A similar need arises where the archaeological context has been lost as in numerous cases where bones are recovered by workmen or other members of the public and handed into the authorities (e.g. case 27 discussion).
However, on those occasions where it indicates human remains dating to post-1955, it initiates further enquiry and poses even more questions. Strontium 90 dating of bone offers limited potential because it is vulnerable to its environment context (Pollard 1996: 148) but work on radio isotopes, particularly lead isotope analysis of bone (210Pb) with a half-life of around 22 years, and also polonium (210Po, with a half-life of 138 days), based on human biokinetic ingestion now shows greater potential with the ability to date accurately within the last 50 years (Swift et al. 2001).
• Is there evidence of either cause or manner of death?
Preserving the integrity of the grave effectively also preserves the integrity of the body and allows it to be examined by the pathologist (and anthropologist) in the configuration in which it was deposited. Careful excavation will ensure that individual elements or skeletal parts will not have been disturbed, thus allowing clear identification of any peri-mortem trauma, and exclusion of obvious post-depositional effects. This will be particularly relevant in examination of the hyoid (often broken during strangulation) or other fractures, including entry and exit wounds. Maintaining this integrity will enable the pathologist to view the individual as a whole and consider the wider implications of how the victim died using the totality of evidence within the defined boundaries of the grave itself. There are, however, two possible exceptions to this: first, projectiles (bullets) fired at point-blank range into the grave may have permeated the body and become embedded in the grave bottom, and, second, toxins from the body may have seeped into undisturbed deposits below the grave. The former may be identified by scanning the emptied grave using a metal detector (and is one good reason why the
archaeologist should remain available until the autopsy is complete). A ballistics expert will be able to provide a better opinion on the depth to which projectiles from different firearms can penetrate certain substrates. The latter can be tested by sampling which is now carried out routinely in most homicide work. It is, nevertheless, useful to co-ordinate the toxicology sampling with the excavation stratigraphy (or spits) as this can provide a better contextual understanding of the burial as a whole (e.g. case 15).
• Who is the victim?
Retaining the integrity of the grave and the position of the victim also serves to ensure that the remains belong to the same individual and that the integrity of the remains for measurement, general identification and DNA sampling purposes can also be guaranteed. If the integrity of the grave is broken, there is a valid cross-examination argument not only that identification may be flawed, but also that items pertaining to identification do not necessarily belong to the victim in ques-tion. Although it is not possible to disprove their stratigraphic association, it is not possible to prove it either. Items in question can include surviving elements of clothing such as buttons, zips, belt buckles, etc., or personal items such as ear rings, watches, finger rings, contents of pockets or metal piercings, which may have fallen from soft tissue and become deposited in the bed of the grave. Recent research (Jackson 2001) has shown that even such personal items as soft-contact lenses can also survive within a burial environment in association with decomposing tissues and still be read for their diopter strength. Clearly, these are only of value if their context is indisputable but they can prove important in ruling various missing persons in or out of the equation. Although not conclusive in their own right, all such information can enable an enquiry to move forward, particularly if the burial has been discovered accidentally without a named missing person or date of disappearance. Conversely, ignoring the integrity of the burial and inadvertently introducing material from layers which are stratigraphically earlier or later can have the effect of sending the enquiry off in completely the wrong direction.
• Was there a transfer of material from offender to grave or victim?
Digging a grave requires manual labour and can be hard work for even the fittest of individuals, given that an estimated ‘average’ grave measuring 2 0.5 0.5m will require removal and replacement/disposal of a minimum of some 0.5 tonnes of earth. During this process the individual will undergo intensive exertion using arms, back and legs during which fibres from clothes, and head hair, may be trans-ferred or dropped to the grave infill, footprints may be left on the graveside or in the grave itself before the body is interred. This is in addition to any accidental transfer of objects from pockets, or through deliberate discarding of material (e.g.
plastic gloves) into the grave fill for purposes of concealment. These will almost certainly be recovered during excavation or subsequent sieving (below), but fibres and hair will be more difficult to observe. The former may be recovered through taping of layers or arbitary surfaces during the excavation process (Wells 2002).
Hair is more difficult to identify and recover, even with sieving, although a single head hair has been recovered from grave fill by one of the authors. Similarly, inexpensive garden spades (or similar) may leave flakes of paint adhered to the
sides of a grave. These are potentially recoverable and can be useful evidence (see case 28).
Footprints tend to be a neglected area of interest but can often underlie human remains in graves of any depth if the substrate is malleable enough to imprint and stable enough to retain that print (e.g. clay). In order to facilitate shovelling soil out of a grave during digging, it invariably becomes necessary to place one foot, or even both feet, in the base of the grave. Footprints, in theory, underlie burials, although the possibility of their survival depends upon the nature of the substrate and other variables. These include difficulties in lifting human remains, wetness brought about by decompositional products, and bioturbation in shallow graves which all make them difficult to identify or preserve (Figure 4.6). Their potential presence, however, adds further emphasis to the need for retaining the integrity of the grave and its boundaries during excavation.
• Is there foreign material in the grave fill and from where did it originate?
Excavation of the grave will be conducted according to well-established principles and by adhering to a defined recording process. All deposits from within the grave will be retained in toto according to layer/spit definition and preserved for future sieving and any pertinent analysis. Reference to test pitting (above) will be able to identify any foreign or unusual soils which can then be earmarked for further investigation, and any obvious or visually distinctive material can be separated out for analysis. They may, for example, represent soils or sediments transported with a body from a former location. Experience has shown that on occasions, foreign material (e.g. bricks, hardcore, timbers, etc.) can be introduced into the grave fill either to provide additional volume to fill up the grave (see case 24), or to provide a false horizon with the fill of the grave (see case 19; Figure 4.7). The corollary of this, however, is in being able to track soils or sediments from a vehicle or clothing back to the grave and demonstrate association. In short, not only will a control sample from test pitting identify material which is alien to the grave, but it will also provide a control for material found elsewhere which may have originated from the grave.