necrosearch revisited

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NecroSearch Revisited:Further Multidisciplinary

Approaches to the Detectionof Clandestine Graves

DIANE L. FRANCETOM J. GRIFFINJACK G. SWANBURG

JOHN W. LINDEMANN

G. CLARK DAVENPORTVICKEY TRAMMELLCECILIA T. TRAVISBORIS KONDRATIEFFAL NELSON

KIM CASTELLANODICK HOPKINS

TOM ADAIR

Introduction

NecroSearch International, Inc. is a nonprofit, volunteer organization dedicated to investigat-ing the methods and technology involved in the location of clandestine graves and the recovery

of the remains and evidence in and around the gravesite. To implement this investigation, therelationships between buried pig carcasses and their surroundings as well as the applicabilityof various techniques in quantifying the changes in the immediately environment surroundingare being studied. The primary purpose of this article is to update the scientific communityon research conducted at the research site, and to cite successes and difficulties with techniquesused at suspected and actual crime scenes. For additional information, please consult aprevious article (France et al. 1992).

The project is an interdisciplinary one involving law enforcement agencies, private busi-nesses, and academicians in an attempt to pool information traditionally obtained separately.

The aim is NOT to state that a specific site is indeed the location of a buried body. Instead,a compilation of all of the techniques indicates a given spot or number of spots that wouldbe the most likely to be the site of a clandestine grave. In addition, these techniques may alsohelp determine time since burial and provide evidence that may tie a suspect to a burial site.As many as practical of the different techniques for site location are being attempted at thetest area. Some of the techniques are suspected of being time-sensitive in that they may be ofvalue only for a limited period of time. A specific sequence may be found to be needed (goingfrom least destructive to most). Some of the results (both present and future) may prove tobe unique to our altitude, soil, etc., so other groups are encouraged to try our approach for

their environmental conditions.

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Currently the NecroSearch team consists of experts in crime scene and laboratory analysis,aerial photography, thermal imagery, geology and pedology, geophysics, geochemistry, petrol-ogy, meteorology, botany, entomology, wildlife biology, criminal psychology, serology, pho-tography, archaeology, forensic anthropology, and scent-detection dog handling.

Background

Few studies in the literature concentrate on multidisciplinary methods used for the locationof buried human remains. Studies by Boyd (1979), Imaiuzma (1974), McLaughlin (1974),and Bass and Birkby (1978, which also offers the rationale behind proper excavation tech-niques) offer overviews of some of the techniques also used in NecroSearch research. Killam(1990) offers a comprehensive survey in search techniques, and Hunter (1994) recently

reviewed various techniques for the location of clandestine graves in the United Kingdom.Although no group has undertaken a study of as many multidisciplinary techniques as

presented in the NecroSearch research, many articles address individual methods for locationof clandestine graves. Davenport et al. (1988, 1990) discuss the ways in which geoscientistswork with law enforcement, while Hoving (1986) describes the use of a small ground-pene-trating radar (GPR) unit for locating buried bodies. Infrared detection of decomposingremains has been tested by, among others, Dickinson (1977) and Rodriguez and Bass (1985).

Other studies have used pigs to research individual aspects of clandestine grave systems.Haglund et al. (1989, 1990, 1991) and Haskell (personal communication 1990) have studied

the scavenging and scatter patterns of pig and human remains. Haskell, in addition, doesresearch on decay processes.

The role of insects and other arthropods in the decay process of human remains has beenreviewed by Nuorteva (1977) and Smith (1986). Studies using unembalmed cadavers or pigshave elucidated a specific succession of arthropods and the resulting decompositional process(Galloway et al. 1989; Payne et al. 1968; Rhine et al. 1988; Rodriguez and Bass 1983; Smith1973; Schoenly et al. 1991; Shean et al. 1993). Rodriguez and Bass (1985) have addressedentomological methods and their relationship to depth of burial and local climatic conditions.Tolhurst and Reed (1984) present information in the training and use of dogs for locating

shallow graves.In an effort to enhance a multidisciplinary approach, many techniques for clandestine

grave-site location are still being applied at the research area in Colorado, and additionallocations involving different environmental conditions will be initiated in the summer of1995. These techniques have also been utilized at dozens of crime scenes.

Location

The primary research site is located on the Highlands Ranch Law Enforcement Training

Facility in Douglas County, CO, approximately 29 km (18 miles) south of Denver. Otherresearch facilities are planned for the mountains west of Denver. As part of a 0.47-km2(117acre) law enforcement training facility, it offers an area of controlled access to the public,though officers in training have used the area occasionally for SWAT-type missions. Thetraining facility occupies a west-flowing drainage that feeds Plum Creek, a major tributary ofthe South Platte River. Elevation at the site averages 1829 meters (6000 feet) above sea level.The research site is on undeveloped ranch land that borders the western edge of Daniels Park,one of the parks of the Denver Mountain Parks system. Topographically the country sur-rounding the training facility consists of gently rolling, brush-covered uplands that change

into partially developed badlands and low mesa topography with increasing elevation. Theupper slopes of the badlands/mesa country support stands of conifer.


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To date, 18 gravesites (two do not contain pigs) have been studied at the research site.Pigs are currently being used for two reasons. At present, human cadavers are unavailable forstudies of this kind in Colorado. Also, these pigs are similar to humans in their weight (70 kgor 154 lbs on average, though smaller pigs have been recently included to simulate human

bodies of different sizes and ages), their fat-to-muscle ratio, and in the fact that their skin isnot heavily haired. Pigs have been considered to be biochemically and physiologically similarenough to humans to be used in studies of patterns and rates of decay and scavenging. Ofequal importance, dog handlers have traditionally maintained that if a dog can detect pigremains, it can also detect human remains.

Methods

Prior to the burial of the first pig in September of 1988, baseline data consisting of black andwhite aerial photographs, geophysical measurements, and geological and botanical observa-tions were acquired for the overall research site. Before the burial of each additional pig,baseline data in electromagnetics, ground penetrating radar, and surface botanical featuresare acquired.

Near-field and far-field data gathering were performed prior to and after burial. Thedefinitions of near-field and far-field are dependent on the specific discipline, in thatnear-field refers to anything that is interacting within the burial system, while far-field isoutside of the range of influence of the burial system. For example, measurements of soil gas

may only be above background levels within a few centimeters of a burial, whereas arthropodactivity related to a burial may cover a much broader area.

Far-field observations contemporaneous with burial for this study include botany, ento-mology, geology/pedology, aerial photography, geophysics, thermal imagery, soil gas, scav-enging patterns, and the use of decomposition-scenting dogs (see Table 1). Near-fieldobservations contemporaneous with and after burial include all of the above. A disturbanceis a physical disruption associated with burial processes. A control site is undisturbed bothat the surface and subsurface, and therefore is remote from the burial site. A calibration pitis a grave without an interred pig, while a grave contains a pig. Back dirt is excess soil deposited

near the perimeter of the grave or calibration pit. It is understood that there are disturbancesgeographically close to the burial system but still identified as far-field in that they are notpart of the burial process for example roads, animal burrows, building foundations, etc.

Aerial Photography

Aerial photography was performed far-field, in an attempt to identify near-field parametersfrom the air. Aerial photographic surveying was performed on a periodic basis, consisting ofboth visible spectrum color and black and white film. A turbo-charged Cessna 205 aircraft

containing two Zeiss RMK/A 15023 aerial cameras and one KA-2

-inch aerial camera wereused. Film types used are Kodak Aerocolor negative type 2445, Kodak infrared color film type2443, and Kodak black and white XX film type 2405. This provides standard 9 in. "9 in.stereophoto coverage.

Geology

Geologic investigation at the Project Pig site determined the geologic character of the site,to relate this character to the individual burial sites, to establish site recognition and evaluationparameters, and to suggest lines of future geologic study and investigation.


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Table 1 Methods Used in the Detection of Clandestine Graves

Method Advantage Disadvantage

Aerial photography Least destructive

Provides great overall characterization of a site; access, culture,

drainage, topography

Large area covered

Preburial photos may be available from a variety of sources

Best results with large film format (scale of readily available photography

may be too small)

May need to be performed at different times of growing season

Natural (trees, etc) and man-made (power lines, etc) may interfere with

interpretations

Requires trained personnel for interpretation

May be moisture dependant

Geology Relatively nondestructiveDetermination of site stratification through core samples

Real time on site information about ground surface

Intrusive if core samples takenEntire search area should be viewed

Botany Relatively nondestructive

Can be performed with photography and samples from area

Can be performed years later

Similar succession patterns for any disturbance within ecosystem not

limited to burial

Entomology Nondestructive

Aids in narrowing site location

Provides information about time since death

Requires limited area for searching

Best for relatively fresh grave

Different species for different geographical regions

Geophysics

Magnetics Relatively nondestructive

Nonintrusive

Equipment easily obtained

Rapid coverage of large area

Works over snow, fresh/salt water

Only for ferrous materials

Target could be missed if search grid too large

Data not in real time; values must be plotted and should be contoured

Magnetic interferences (natural and man-made) confuse readings

Electromagnetics Relatively nondestructiveNonintrusive

Rapid coverage of large area

Equipment relatively easily obtained

For ferrous/nonferrous materials

Records conductivity

Works over/through snow

Subject to cultural (fences, etc) interferencesTarget could be missed if search grid is too large

Difficult in rough terrain

Data not in real time; values must be plotted and should be contoured


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Ground penetrating radar Relatively nondestructive

Nonintrusive

Fairly rapid coverage of large area

Real time display

Works over/through snow, fresh water

Equipment relatively difficult to obtain

Most units require moderately smooth and level terrain

Self-potential Relatively nondestructive

Real-time information

Intrusive

No worthwhile information from our research

Soil gas Relatively nondestructive

Real-time information

Intrusive

Must be positioned relatively close to burial

Site soil, ground moisture, climate, depth of probe critical

Detection of decomposition product(s) time and temperature dependent

Metal detector Relatively nondestructive

Nonintrusive

Equipment easily obtained

Limited depth capability, detects only metal (ferrous/nonferrous)

objects, presumes metal objects on or with body

Field application often improperly conducted

Thermal imagery Nondestructive

Can examine large area

Hand-held or attached to vehicle (land or aircraft)

Real-time data

Videotaped for review

Requires little or no wind

Requires special equipment and knowledgable operators

Decomposition dogs Relatively nondestructive

Documented effectiveness even 170 years after burial

Effective over water

Most effective when air, ground moist

Dog may be trained for other uses and not properly trained for this type

of work; handler may overstate qualifications

Naturalists Excellent for information concerning scavenging cases and

outdoor information

Ability to recognize animal scavenging may be altered by climatic

conditions

Tracking easiest in snow, mud, soft sand, or dust

Archaeology Experienced in mapping, data collection, preservation of

information from excavated materials, and is therefore

extremely valuable for building court cases.

Both destructive and intrusive

Though data collection can be modified to meet most time demands,

can be relatively slow

Forensic physical anthropologists On-site interpretation of remains

Locations of skeletal/body elements

Not all forensic physical anthropologists are trained in excavation

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Literature research and far-field studies were performed to establish the geologic characterand stratigraphic setting of the project site. This involved definition of rock types, establish-ment of the age relationships among the rock types, and the evaluation of the effect of rocktype on subsequent soil formation. Far-field studies also involved relating the physical character

(geomorphology) of the project area to the distribution of underlying rock types (stratigraphy).The near-field studies on the sites and the related far-field studies focused on the defini-

tion of soil profiles at specific burial sites, road cuts, and other excavations; the relationshipof these soil profiles to the parent rock units; and how soil composition and character affectthe recovery of a soil profile to a normal state. All burial sites have been and continue tobe monitored and photographed to document the recovery of the soil profiles.

This program involved photographing of each burial site on a monthly basis. In addition,soil samples were collected to monitor soil disintegration as a reference to actual disturbancerecovery at the burial sites.

Botany

As part of the far-field study of vegetation, percent area cover for bare soil (back dirt), litterand herbaceous vegetation were estimated, and a total species list was prepared listing theplants found within the training facility.

Near-field study of vegetation included listing the plants growing on each grave, calibra-tion pit, and back dirt area. For the near-field study, a 1-m by 0.5-m rectangle of PVC pipewas set at the approximate center of the test plot (grave, control pit, etc.) and vegetation wasanalyzed from within that test plot. Far-field study was tested in the same manner, with the1-m by 0.5-m rectangle of PVC pipe set at various areas away from the test plots. The areasfor far-field study are not the same for each test, but are taken approximately at randomwithin the training facility in the general vicinity of the test plots. Frequency of species wasdetermined by counting the number of rectangular plots on which a particular plant specieswas found. For example, wheat grass was found on four disturbed plots (either a grave orcalibration pit) and on two undisturbed sites, while sunsedge was found on no disturbed sitesand on three undisturbed sites.

After the pigs were scavenged from sites #1, 2, and 5, members of the team decided tocover the unscavenged grave sites with heavy chain link fencing to protect those graves fromfurther scavenging. Although vegetation on the grave is potentially altered, some plant growthis allowed, and the fencing can be easily removed for near-field investigations such as geo-physical surveying.

Entomology

A control site was established to examine the airborne and surface insects. A BioQuip Malaisetrap was erected to monitor aerial-dispersing insects, and was cleaned of all insects 1, 2, 4, 7,12, 15, 25, and 30 days after pigs were buried. In addition, this type of trap was erected directly

over burial site #1 and cleaned of all insects at the above schedule. Additionally, five pit trapswere placed around the site to sample surface dispersing arthropods, and were monitored andcleaned at the above schedule. At burials 12 and 13 (surface deposits), insects were collectedat the same intervals.

Geophysics

Three specific geophysical methods were selected for evaluation at the Pig site: magnetics(MAG), electromagnetics (EM), and ground penetrating radar (GPR). The selection of these

methods was based on the direct experience of one of the authors (Davenport) in implement-ing geophysical investigations on archaeological projects. The equipment utilized to date hasincluded an EG&G Geometrics G-856-AX proton precession magnetometer with gradiometer


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attachment, Geonics EM-31 and EM 38 ground conductivity meters, and a Geophysical SurveySystems, Incorporated (GSSI) subsurface interfacing radar (SIR) Model SIR-3 with magneticdata recording and color display capabilities. The GPR system has been evaluated using 80,300, 500, and 900 megahertz (MHz) antennae. Self potential (SP) surveying has also been

utilized at the research site, but not as extensively as the other geophysical methods. The soilgas (SG) surveying was performed utilizing a Photovas 10570 portable gas chromotograph,while the SP surveying was done with a BBC high impedance voltmeter and Tinker and Rasorelectrodes. Geophysical surveying was performed in either lineal or grid arrays, with datacollection points spaced from 1 to 3 meters apart, except in the case of GPR surveying, whichproduces a continuous record of data collection. Geophysical arrays were arranged to providedata over undisturbed areas, buried pigs, and control pits.

Thermal Imagery

The initial thermal imaging was performed using a Xedar Model XS-420 infrared camerasystem. Current surveys are conducted with FLIR (Forward Looking InfraRed) Systems, Inc.,model #2000F with a truck mount, and ISI VideoTherm Model 94 and Model 96 portablehandheld infrared cameras. Fair-field thermal imagery consisted of obtaining high qualitythermal images of steady-state and dynamic scenes by panning the camera across the terrainof the research site, whereas near-field information was obtained by aiming the camera towardand fixing it on each grave and calibration pit.

Soil GasSoil gas sampling of the far-field consisted of determining background levels of methane andother volatile organic compounds throughout research site. Near-field studies were performedby taking soil gas readings directly over graves and calibration pits.

Decomposition Dogs

Standard far-field and near-field investigations become less defined for work with scent-detection dogs, as the dog defines those fields itself. The ability of the scent detection dogs to

locate the buried pigs was tested using standard search techniques. The dog was controlledon a lead of usually 5 meters (15 feet) in length at all times, and worked on a zigzag patterndownwind of the suspected area. The zigzag pattern was maintained for the dog until it alertedto a scent, at which point the dog was allowed to work its own search pattern to the source.

Scavenging Patterns

Naturalists trained in animal tracking and familiar with the habits of indigenous species wereresponsible for identifying scat and other animal sign. This information was used to developscavenging patterns related to the burial sites. Patterns of bone modification related to scav-enging were studied.

Standard far-field and near-field investigations also became blurred in studies of scav-enging, as those terms are defined by where the scavenged remains, scat, and the agents ofscavenging (coyotes, dogs, rodents, etc.) are found.

Results

Aerial Photography

Grave sites are revealed by a number of factors in the air photographs taken at the research site.These factors include changes in growth patterns and characteristics of near-field vegetation,


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anomalous soil marks associated with excavational boundaries, and settlement of snow withinsome grave surface depressions. Low sun angle oblique photographs tend to emphasize textureof the ground surface, and the associated long shadows can reveal minute topographic relief.

Thermal Imagery

Aerial photography has been combined with infrared photography (forward-looking infrared,or FLIR) to search for buried bodies. While the FLIR system offers the best possible resolutionand clarity, it requires a mount only offered by a helicopter or a specially equipped truck.

The use of infrared should not be limited to detecting those heat-related changes asso-ciated with decomposition. Infrared is a valuable tool in detecting compaction or densitydifferences between the disturbed and undisturbed ground and so can be useful in detectinggravesites years after heat-generating decomposition has ceased.

Geology

At the research site, short-term (less than 5 years) geological effects are enhanced by climaticconditions. The climatic conditions that typify Colorados eastern plains offer extreme con-sequences affecting both the soil character and the rate and nature of soil recovery over thegraves. Climatic conditions during late spring, summer, and fall, and often into early winter tendto be dry. The dry conditions are inhibiting plant reestablishment over the graves and retardbreakdown of the disturbed clay rich host soil horizon. Lack of moisture largely neutralizesmechanical breakdown of fill material that is characteristic of periodic freeze/thaw conditions.

The moist climatic conditions of winter, spring, and early summer enhance rapid break-down of clay soils. Excavation boundaries tend to become masked, fill material becomesgenerally more fine-grained, and the compaction of the fill material to the original surfacegrade is facilitated.

Excavations made during dry climatic conditions persist with little change throughoutthe dry season. Moisture enhances grave site recovery and plant establishment.

Botany

The consequences of digging a grave and burying a body in a natural area are the same asany type of disturbance that destroys the existing vegetation: secondary succession is set intomotion. After 5 years of following the regrowth of vegetation on pig graves, several generalobservations can be made. Undisturbed plots contained the greatest species diversity andsupported both weedy plants as well as wild flowers. After disturbance by digging, theplots supported a community with very little species diversity, often a monoculture ofAlyssumminus

(in this area of Colorado). Slowly, other species are invading from the surroundingundisturbed areas, but no plots had attained the original species mix by May of 1994. Thereis no difference in the revegetation pattern between the holes that still contain pigs and the

holes that do not contain pigs.The graves and calibration pits continue to revegetate, though the mix of plants on the

disturbed areas is noticeably different than on the undisturbed areas. Vegetation on thedisturbed areas depends on several factors, including which plants are nearby and supplyingseeds to the disturbed ground and where in the landscape the digging was done (in drainageareas or on high ground). For example, the pig at Site 6 was placed on top of the ground ina drainage ditch, and dirt from another area was deposited over it. Even though the pig wastaken by scavengers, the disturbed area is revegetating differently than the rest of the sites,both because the seeds in the foreign soil are different from the indigenous plants, and because

the drainage ditch provides extra water for growth.Although the percent cover for each site does not differ, the species covering each site are

different. After 5 years the grave sites are revegetating similarly to the calibration pits, and,


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though it is commonly believed that the presence of a decaying body will provide nutritionto the plants covering a gravesite, at this point the presence of a decaying pig has not obviouslyaffected plant growth, though decomposition dogs used in the research and on search sceneshave indicated on some species of plants surrounding gravesites. (See section on decompo-

sition dogs.) The warmth provided by a decaying pig has not been seen to affect the plantspecies which occupy a gravesite, though it is still hypothesized that this warmth exceedingthe temperature of the adjacent ground may encourage plants to stay active for a longer periodof time than the surrounding plant colonies during the period of heat-generating decay.

Vegetation analysis on the eight sites shows that:

1. Digging a grave will destroy existing vegetation and set succession in motion.2. Pioneer or opportunistic plants will be the first to grow on the disturbed area. At the

research site, the plants that have shown up on disturbed plots that have never shown

up on undisturbed plots are thistle (

Carduus

spp.), annual sunflower (

Helianthusannuus

), and common purslane (

Portulaca oleracea

).3. Vegetation changes as the grave progresses through the serial stages of succession.4. Presumably, the climax vegetation for the area will eventually grow on the graves and

calibration pits if they are not further disturbed. For lowland dry grass areas thisincludes blue grama grass (

Bouteloua gracilis

), other grasses, and many wild flowers.The disturbed area (grave or calibration pit) will look different from the surroundingarea for many years (exceeding so far, the duration of this study).

5. Knowledge of the plants of an area can supply clues to the discovery of a grave,

particularly where the vegetation is largely otherwise undisturbed.

Entomology

There was no visible entomological indication of the buried pig, such as evidence of surfacestains from saponification/liquification ca. 30 days after burial. The blowfly, Calliphora vom-itoria,

was trapped by the Malaise trap within 24 h of burial, and Phormia regina

arrived 48 hafter burial. By day 15, significant numbers (

p

=


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electrical properties of the soil, GPR surveys offer the investigator the most useful tool todelineate graves. Soil changes and excavation patterns can be readily identified by trainedGPR operators. The addition of color monitoring to the normally black and white monitoringcapabilities of the GPR systems allows investigators to easily identify changes in soil horizons

over actual grave sites.Perhaps the most important result of the geophysical surveying at the Pig site has been

the realization of the importance of constructing a calibration site to test any geophysicalmethod prior to application on an actual investigation. Any information concerning the typeand/or construction of the disposal facility should be used to construct a similar, albeit empty,facility near the actual area to be investigated. The geophysicists can utilize this calibrationsite to determine the following:

1. Response of different geophysical methods

2. Type and characteristics of the geophysical signal3. Profile and data station separation(s)

Soil Gas

The soil gas surveying performed at the research site holds promise of providing a useful,albeit labor intensive, technique to locate graves. Organic gases were detected within 3 metersof two of the grave sites; however, the investigators had the privilege of knowing in advancethe locations of these sites. Soil gas surveying is best in soils with a low clay content (so asnot to clog the probes) and over unfrozen ground. Soil gas is not routinely utilized at crimescenes by the NecroSearch team.

Decompostion Dogs

Based on experience with cases in this study and on opinions of other dog handlers, thesuccessful use of dogs seems to be most significantly affected by weather conditions. Thereappears to be a decrease in the dogs scenting ability at temperatures above approximately29C (85F). Excessive heat apparently causes some discomfort to the dog which seems todecrease its ability to locate a scent. When the temperature is extremely high, the dog may

still locate the scent; however in most cases it will need to be within approximately 1 m of aburied source. Even if the temperature is high, the results will improve if the ground is moist.Extremely low temperatures also seem to limit the dogs ability to detect the scent from adistance, especially if the source is buried. If the source is buried in snow with temperaturesallowing only minimal melting, the dog must be within 1 meter to locate the source. If thetemperature is warm enough to allow for significant melting, the dog can locate the sourcefrom a greater distance. Additionally, if the source is buried in snow, or in the ground belowsnow, and the temperature is below freezing, the dog may not locate the source at all. Theprecise relationships between temperature, burial, and wind have not been tested.

Other factors which appear to affect the dogs work include air humidity, ground mois-ture, and wind speed. Humidity seems to intensify the dogs ability to detect the source at adistance. The ground should be moist, ideally to the depth of the source, or so dry thatdesiccation cracks intercept the source (Major Glenn Rimbey, New Mexico State Penitentiary,personal communication). Ultimately, if no wind is present, the dog will have difficultydetecting a scent except from an area within a meter of the source.

Based on experience at the research and other sites, the optimal conditions for thesuccessful use of cadaver dogs include temperatures between approximately 4 and 16C (40to 60F), 20% or higher humidity, moist or very moist ground, and wind speed of at least

8 km (5 mi) per hour (there is no upper limit to wind speed, though the scent cone becomes


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narrower with higher wind speeds). Additionally, it has been hypothesized, but not tested,that lower barometric pressure may increase the ability of the dogs to detect scents of all kindsarising from the soil.

Also based on experience at the research site and other sites (including actual cases), the

trained decomposition dog will indicate the presence of decayed human scent when the sourceis human blood, feces, urine, and other human compounds, as well as other materials thathave been handled or worn by humans, and so will give a seemingly false positive indication.Due to this discovery the dog handlers involved in this research have reclassified their dogsas decomposition dogs rather than cadaver dogs since a positive reaction from the dogmay not specifically indicate a cadaver. Also, the dogs have marked on particular spots wheredecomposing scent had been present but had since been moved either accidently or purposely.Double-blind tests are being devised at present to rigorously test the dogs and handlers todetermine under what additional conditions false negatives are possible (that is, when the

dog does not indicate a body which is present).Additional tests are being devised to determine the maximum time since death in which

dogs can be useful. Some cadaver dogs have indicated on archaeological remains dated toaround 1400 years before the present in an above-ground informal test. As expected, the dogsare less likely to indicate on those pig burial sites with a longer time since burial interval.In those situations, however, the dogs are more likely to indicate on certain plant species(particularly shrubs and trees) surrounding the grave site, and in some cases the dogs haveactually tried to chew or bite at those shrubs close to the grave site (which is atypical behavior).

Scavenging

Animal tracks or scat identified in the research area include domestic dog, coyote, fox, rabbit,deer, elk, skunk, raccoon, horse, cattle, porcupine, woodrat, and mouse.

Intensive, systematic searches within a 1 km radius of the site have recovered bones ofdeer, cattle, horses, canids, and rabbits. Many fresh bone chips, teeth, and hair had been foundaround several sites, indicating scavenging, but no large pig bones had been recovered withinthat search radius of the pig burials in the earlier stages of the research. The absence of largebones within the search radius suggested that the remains were carried a greater distance thanthe approximately 0.2 km maximum reported by Haglund et al. (1989), though as Haglundmentioned (personal communication), the ranges of coyotes vary considerably with differ-ences in terrain and vegetation. Small VHF transmitters designed for wildlife radio trackingwere recently attached to various areas of several new pig carcasses before burial to trace thelocation of the scavenged remains. The greatest distance to date for removal of portions ofthe pig remains has been 300 meters (burial 13), but remains may be moved as little as a fewmeters at each time, shallowly buried by the scavenger, and moved again later (as recordedwith the aid of the transmitters).

Birds (various hawks, turkey vultures, and other birds) are often the first scavengers onthe scene of shallow burials or surface deposits and will visit the remains many times through-out the scavenging process. Initial observations suggest that birds may take the epidermis ofthe pigs in sheets leaving straight surgical-like cut marks on the remaining tissue. In futureexperiments, this material will be preserved for microscopic examination and comparisonwith true cut tissue.

Conclusions

Table 1 has been prepared based upon the experiences gained by both studies done at theknown (pig) burial sites and field work on sites of suspected criminal burials.


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