Standard Guide for the Collection of Soils and Other Geological Evidence for Forensic Applications 1

Transcription

1 Standard Guide for the Collection of Soils and Other Geological Evidence for Forensic Applications 1 This standard is issued under the fixed designation X XXXX; the number immediately following the designation indicates the year of original adoption or, in the case of revision, the year of last revision. A number in parentheses indicates the year of last re-approval. A superscript epsilon (ε) indicates an editorial change since the last revision or re-approval. 1. Scope 1.1 The following is a guide for the collection and preservation of soil evidence at crime scenes. It is designed as a resource for forensic scientists, law enforcement personnel, and other professionals whose job responsibilities include the collection and preservation of soil evidence at crime scenes. This guide is intended to serve as a resource for the development of individual agency procedures regarding the collection of soils and other geological evidence for forensic applications. It is not a substitute for a formal training program in crime scene processing, but may be used as a supplement to such training. 1.2 The units of measurement in this document are provided in both metric and English units for ease of use. 1.3 This standard does not purport to address all of the safety concerns, if any, associated with its use. It is the responsibility of the user of this standard to establish appropriate safety and health practices and determine the applicability of regulatory limitations prior to use. 1.4 This guide offers a set of instructions for performing one or more specific operations. This document cannot replace education or experience and should be used in conjunction with professional judgment. Not all aspects of this guide may be applicable in all circumstances. This ASTM standard is not intended to represent or replace the standard of care by which the adequacy of a given professional service must be judged, nor should this document be applied without consideration of a project's many 1 This Guide is under the jurisdiction of ASTM Committee and is the direct responsibility of Subcommittee. Current edition approved XXX. XX, XXXX. Published XX XXXX. DOI: /XXXXX-XX.

2 unique aspects. The word "Standard" in the title of this document means only that the document has been approved through the ASTM consensus process. 2. Referenced Documents 2.1 ASTM Standards: 2 E1732 Standard Terminology Relating to Forensic Science 3. Terminology 3.1 alibi location(s), n a known source of soil material, suggested by or linked to a subject (i.e. locations at a subject's home) and distinct from the scene of interest 3.2 clod, n a compact, coherent mass of soil varying in size, usually produced by plowing, digging, etc., especially when these operations are performed on soils that are either too wet or too dry. They are usually formed by compression, or broken from a larger unit, as opposed to a buildingup action as in aggregation 3.3 clump (soil), n a small clod 3.4 known sample(s), n - of established origin associated with the matter under investigation 3.5 ped, n a unit of soil structure such as a block, column, granule, plate, or prism, formed by natural processes (in contrast to a clod, which is formed artificially) 3.6 questioned sample(s), n associated with the matter under investigation about which there is some question, including, but not limited to, whether the questioned and known items have a common origin 2 For referenced ASTM standards, visit the ASTM website, or contact ASTM Customer Service at [email protected]. For Annual Book of ASTM Standards volume information, refer to the standard's Document Summary page on the ASTM website.

3 3.7 random number generator a computational or physical device designed to generate a sequence of numbers or symbols that lack any pattern 3.8 soil, n sediments or other unconsolidated accumulations of solid particles (e.g. minerals and organic matter) produced by the physical, chemical, and biological disintegration of parent material and/or has the ability to support rooted plants in a natural environment; and which may or may not include manufactured materials 3.9 and differing from adjacent genetically related layers in physical, chemical, and biological properties or characteristics such as color, structure, texture, consistency, types and numbers of organisms present, degree of acidity or alkalinity, etc soil core sampler, n a device used to collect virtually undisturbed sub-surface soil samples for soil profiling and environmental investigations. An example of this would entail the insertion of a hollow cylinder (made of plastic or metal) into an exposed soil profile. A small, shallow version of a soil core sampler may be referred to as a "soil sample cutter" soil micromonolith tray, n a small box that holds a representative vertical section of a soil profile removed from the parent soil and mounted for display or study 3.12 soil profile, n a vertical section of soil exposed from the ground surface to a depth of interest. A soil profile may be observed in a freshly dug pit, along a road bank, or in many other places soil horizon, n a layer of soil or soil material approximately parallel to the land surface 4. Significance and Use 4.1 This guide describes the techniques associated with the collection of soils and/or geological materials (collectively referred to as soils throughout the remainder of this document) for forensic purposes. Examples of the geological materials encompassed in this document include soil, dust,

4 debris, sediment, sand, gravel, etc. This guide outlines practices for the documentation, collection, and preservation of soils found associated with evidence items (e.g. questioned samples) and from known sources that may be associated with the questioned samples (e.g. samples from the crime scene or other site). The goal of forensic soil sampling is to obtain soil evidence which provides an adequate representation of known locations and as complete a representation of the questioned sample(s) as possible. Proper soil sampling techniques increase the robustness of soil provenance and comparison casework. 4.2 Wherever possible, soil evidence that is present on an item (e.g. a mud clump on a shoe) should be maintained intact; ideally, the entire item should be collected and carefully packaged to preserve the soil evidence in its original state. It is desirable to minimize the handling of soil evidence after collection and prior to analysis. This ensures that fragile, layered soil evidence maintains its structure during delivery to the laboratory. 4.3 If the laboratory to which the evidence will be submitted is known, make contact with the appropriate laboratory personnel to obtain any needed background information and to ensure that proper collection, preservation, and submission procedures are used. When laboratory personnel are unavailable, additional sources of assistance may include scientists from the USDA-NRCS-Soil Survey, the USGS, soil scientists or geologists from private companies and/or universities, etc. 5. Procedure 5.1 Collection of soils: The goal of collecting soil samples for forensic analysis is to provide an adequate representation of the location of interest.

5 5.2 Goals. Soil and geological materials may be collected for a variety of reasons (e.g., comparison, investigative purposes, or for determination of a geographic source) and from a variety of locations (e.g., a vehicle, body, the ground, a grave). In general, samples to be collected will fall into one of two categories Questioned Samples. Questioned samples may be collected from virtually any substrate, which may include vehicles, bodies, clothing, shoes, or off of another soil. In general, it is best to preserve such samples in place for later sampling in a laboratory. In some instances, samples may need immediate attention to preserve layer structure, in which case, care should be taken to avoid further disturbance of any visible layers or structures Known Samples. Known samples may be collected from a variety of locations, including suspected source locations and/or alibi locations Background information. Obtaining background information prior to the collection of any samples is extremely beneficial for the purpose of ensuring that appropriate samples are collected. The types of background information which can be gathered include case information, soil survey information ( geological survey information, appropriate maps (including geo-political, topographical, road, geological, and soil survey maps), and the exact location of the collection site, including GPS coordinates or equivalent Considerations of environmental alteration. Geological evidence and other related materials (such as botanical evidence) may be subject to environmental alteration or degradation over time. For this reason, such evidence and related reference samples should be preserved and collected as early as possible in the course of an investigation. This does not preclude the possibility of collecting additional samples at a later date.

6 5.2.4 Locations. Areas to be sampled may include crime scenes, alibi locations, burial sites, and any additional relevant sites where questioned soil may be found or may have originated. 5.3 Collection strategies: When processing a location, there are several different strategies which may be employed for the collection of samples. The particular strategy used will depend upon case circumstances PURPOSEFUL This approach is useful when specific areas of interest have been identified. Such specific areas of interest may include areas of entry, areas of egress, burial sites, areas of disturbance, footwear or tire impressions, areas with visual (texture or color) similarities to questioned samples, or areas with appearances anomalous to the surrounding materials. For examples of this type of collection, see Geological and Soil Evidence SYSTEMATIC This approach is a pattern-based technique for the collection of samples. A variety of patterns may be used, to include grids, circular patterns, compass points, etc This technique may be of value when there are no obvious features from which to sample (e.g. looking for a burial site or buried object) or for sampling around a single object of interest (such as a body) when no other features (such as shoeprints or tire impressions) are present. For examples of this type of collection, see Geological and Soil Evidence Example: If suspects claim that the soil on their shoes came from somewhere in their backyard, and the yard is a featureless lawn, a systematic sampling approach may be warranted RANDOM 3 Pye, K. Geological and Soil Evidence: Forensic Applications. Boca Raton, FL: CRC, Print.

7 This approach is typically used for research purposes and environmental casework. Random collection points may be chosen from a map, a random walk through the site, or the technique of using a random number generator to mark sampling sites on a map or drawing For example, if an environmental contamination case required the evaluation of the background concentration of a particular soil constituent within the soil (e.g. cadmium) in an agricultural field, a random soil sampling technique could be employed to develop a statistically defensible mean background concentration as well as an assessment of the variability of cadmium across the field COMBINATION Many cases may benefit from a combined approach including both purposeful and systematic sampling techniques When processing a crime scene, a systematic sampling plan minimizes individual bias and ensures that soils will be collected from a wide range of locations at the scene. However, the purposeful sampling ensures that soil from important features not included in the systematic plan (such as likely paths of entry and egress) is collected The number of samples collected is case- and scene-dependent In locations with no or low distinct visual variability, a number of soil samples should be collected in order to encompass potential variations within the scene High levels of visual variability in a location may require a larger number of collected samples Complex locations encompassing a large number of points of interest may also require a large number of collected samples.

8 5.4 Collection tools: Tools should be chosen to minimize damage and corrosion, and should be easy to clean, thereby preventing contamination from either the tool itself or a previously collected sample. Examples of suitable non-porous materials for tools include hardened or stainless steel tools (for harder materials) or plastic tools (for softer materials) The shape and size of the tools used for collections should be selected to enable the isolation and preservation of small, discrete samples where necessary Some tools commonly used are spatulas, dental picks, forceps, tweezers, spoons, pointed (archaeologist's) trowels, spades, pallet knives, soil corers, and soil micromonolith trays For example, a knife may be used to carefully excavate clod from within a soil profile Collection tools for atypical/special circumstances: While the above tools are recommended for most collections, there are circumstances where other specialized collection methods are appropriate. The following tools may be used in the field for the collection of thin soil deposits or dust or when the substrate cannot be delivered to the laboratory. It is important to note that scraping, sweeping, brushing, vacuuming, or swabbing can create mixtures and potentially destroy structural, pattern, or impression information within the sample. Questions about the use of these techniques for soil collection or their possible detrimental effects upon the evidence should be addressed to the personnel of the laboratory receiving the evidence Clean (or new) razor blades, spatulas, ice scrapers, or other flat, suitable implements may be used for scraping Clean/new brushes and collection pans should be used for sweeping or brushing A specialized vacuum set-up is required for vacuum collections.

9 Swabs (sometimes dampened with water). Swabs constructed from polyurethane foam are preferred; however, swabs made from viscose rayon or other man-made materials are acceptable and are preferred to cotton swabs Tape lifts should be made using tapes with a low level of tackiness (such as frosted tapes) rather than with fingerprint lifting tapes Care of tools: An item is sufficiently clean when no particles are detected on a clean cloth used to wipe the tool In most circumstances, non-disposable tools may be cleaned by rinsing with clean water or a solvent. Alcohol or a bleach solution may be used to assist with the drying and to help with the decontamination of tools used to collect samples with biological components. Tools that cannot be cleaned should not be reused. 5.5 Collection techniques: Collection techniques and tools (mentioned in the previous section) should be selected to fit the appropriate situation/conditions in order to avoid cross contamination, ensure sufficient sample size, capture the variability present in the soil at the site, and preserve the integrity of any visible layers or structures present in discrete samples Soil and geological materials may change over time. Both natural and man-made events have the potential to modify, radically alter, or destroy certain sample properties such as structure; therefore, samples should be collected as close to the time of the event as possible Surface collections: surface samples are collected from either the top soil horizon (layer) of a soil or from the depth of any existing impressions (such as tire tracks or footwear impressions).

10 Collect grams [2 3 tablespoons] per sample to a depth of approximately 1 2 cm [1/2 to 3/4 inch] or to the depth of any existing impressions of interest. Coarse-grained materials, such as gravel or pebbles, require a significantly larger sample size Collect separate samples from areas which are visually distinct (e.g. different in color or texture). Note that such differences may occur even within a single impression If distinct impressions are present, samples should be collected from an area as close as possible to the impression. Multiple samples should be collected from the areas surrounding the impression so as to encompass any variation present. For examples of this type of collection, see Geological and Soil Evidence Once impressions have been documented/photographed/casted, samples may also be collected from within the area of the impression (sidewalls and floor) When no distinct impressions are present, a combination of purposeful and systematic sampling techniques appropriate to the location is recommended Sub-surface collections: Soils vary with depth. Variations may be visual (color, structure, and texture) or composition-based (chemical, mineralogical, physical, biological content, etc.). Therefore, in locations where soil has been removed from areas below the surface, including, but not limited to, burial sites, holes, river banks, cut banks, or deep tracks or ruts, collections should be made to encompass any variability present with increasing depth Attention must be paid to the appearance of the side walls of any excavation, as toolmarks or other impressions may be present. These should be documented appropriately and preserved prior to any soil collection. Such marks may also be excised and collected intact for further analysis.

11 Samples from each visually distinct area should be collected separately. Such areas may encompass distinct layers, horizons, or distinguishable clods or peds. Additionally, if disturbed soil or a spoils pile is present, samples distinguishable from each other may be collected from these sources When no visually distinct layers are present, a systematic sampling technique is recommended to make collections throughout the depth of the hole. Samples should be collected at regular intervals of approximately cm [6 to 12 inches] to the depth of interest Background samples should be collected from an undisturbed area adjacent to the burial site at similar depth intervals to the same depth as the excavation Approximately grams [2 3 tablespoons] per sample should be collected. Coarse-grained materials, such as gravel or pebbles, require a significantly larger sample size To obtain a representative sample from the depth profile, collect small samples from each layer or horizon and package them separately. To preserve the depth profile intact with any layer structure present in the soil, collect core samples or sidewall samples using soil micromonolith trays or soil core samplers If the soil horizon in the depression has been compromised, mixed, or cannot be observed, a depth profile may be observed by excavating a soil pit in close proximity to the original site and collecting representative samples of the profile Samples from sites excavated in sloped areas should be collected from each of the sides and labeled in relation to slope aspect so as to precisely identify the location from which the sample was collected, including the orientation of the excavation of interest.

12 A sample should also be collected from just below the base of any depression or excavation. For example, when a body is present, a sample should also be collected from the undisturbed soil just below the body. See above for more advice on soil collection at body deposition and burial sites Collections from objects: Soil and other geological materials may be retained on the surfaces and in crevices present on a variety of objects that cannot be delivered to the laboratory. Special care should be taken to preserve any depositional (structure or layer) information present Collection(s) of consolidated soil: Peds, clods, or clumps of soil may contain useful structure and layering information which should be maintained. See section for advice on packaging these collections These samples can be very fragile and should be collected and carefully packaged in separate packages by wrapping in aluminum foil such that the structure can be preserved for observation at the laboratory Collection(s) of unconsolidated thin deposits or dust: Where possible, the entire item (tool, car floormat, etc.) bearing the deposit should be submitted to the laboratory. Where this is not possible, the deposits should be collected as discussed below Methods commonly used to collect thin deposits, using the tools discussed in Section are as follows: Scraping Scraping may be suitable for the collection of thin deposits or dust upon nonporous surfaces such as windows Sweeping and brushing

13 Sweeping and brushing may be appropriate for the collection of deposits from locations such as floors A clean/new brush should be used for each independent sample collection Vacuum collection Vacuum collection requires a specialized set-up and will destroy any layers or structure information present. A forensic vacuum should be used. Any issues with collection, filters, etc. can be addressed to the manufacturer, though all sensible precautions should be taken by the collector Any questions or concerns regarding the use of any vacuum system or its possible detrimental effects upon the evidence should be addressed to the personnel of the laboratory receiving the evidence Vacuum collection should not be used for larger samples, but may be suitable for the collection of dust samples of very thin deposits on non-transportable surfaces, to include such items as paved areas, concrete surfaces, or flooring Swabbing The use of swabs may be appropriate when collections are made from a body or to collect a thin deposit from other non-porous surfaces that cannot be delivered to the laboratory Swabs which have been moistened should be allowed to dry prior to packaging or packaged so as to enable the drying of the sample without the loss of any recovered evidence Tapelifting

14 Tapelifting of soil or geological materials should not be performed with high tack tapes or those used to lift fingerprints as the adhesive material on these tapes interferes with the recovery and analysis of the sample. As an alternative, tapes with frosted backings may be used as these tapes tend to have lower tack adhesives Tapelifting may be appropriate for the collection of thin deposits on certain porous materials (such as fabrics) that cannot be delivered to the laboratory. See section for advice on packaging these collections Non- indigenous soils: Soils and other geological materials may be transferred to a location by various means, including via footwear or vehicular undercarriages. Be aware that individuals responding to the crime scene may bring soil from foreign locations with them on their shoes and may also move soil from place to place within a crime scene Soil materials which appear different from the immediate surroundings should be sampled separately In many cases, such transfers occur in smaller amounts and the entire sample should be collected for submission Collections from bodies: Non-indigenous soil and other geological materials may be recovered from on, near, or, in rare occasions such as rape or homicide, from within a body, and may be particularly important evidence when a body has been moved from one location to another prior to discovery It is important to ensure that proper steps are taken to preserve any material on the body which may be lost after the body is moved and/or transported.

15 If soil cannot be collected from a body due to jurisdictional restrictions, then advise the appropriate personnel regarding the need to preserve the integrity of the soil evidence during transport. 5.6 Documentation, preservation, packaging, and transportation of samples: After collection, it is crucial that soil and other geological materials are submitted to the laboratory in a condition that adequately represents their original state. Samples should be handled minimally and protected from deleterious or structural changes, contamination, and inadvertent loss. Proper documentation, preservation, packaging, and transportation of soil samples are essential for maintaining the integrity of soil evidence. Sample packages should be properly sealed using tamperevident methods Samples may be stored in containers which can be sealed tightly and which are impervious to corrosion from the contained samples. Suitable containers include screw-top plastic containers (plastic specimen cups), paper or aluminum foil packets (bindles or pharmacy folds), zipsealed plastic bags, screw-top centrifuge tubes, and lined paint cans Soil materials can be easily lost from containers such as paper envelopes or bags, therefore, the use of these containers is not advised Swabs used for the collection of samples should be placed in a size appropriate, sealable container. Plastic bags are strongly discouraged due to static electricity Tapelifts of soil samples may be placed sticky-side down on a material such as a clear sheet protector. The material with the tape should then be sealed in an outer container for submission. The tapelifts should NOT be placed sticky-side down on materials from which they would be difficult to remove (such as paper) which may contaminate the sample.

16 5.6.2 Any layer structure present in the samples should be preserved during the collection, packaging, and submission to the laboratory Possible methods for the preservation of soil clods collected within layers include wrapping in aluminum foil or using clean cotton or another filler material to pad the sample within its container (to prevent breakage during transport). It is important to ensure that the filler material selected is not something which may compromise analysis, including any padding material containing geological materials, such as vermiculite It is preferred that wet or moist samples be immediately transported to the laboratory, and that the laboratory is notified when such samples are being submitted Moist samples which cannot be immediately transferred to the laboratory should be dried at room temperature in a secure location while covered with a breathable material (e.g., paper products) so as to prevent environmental contamination of the sample If human DNA analysis is expected, freeze the sample immediately (-20 C) and contact the appropriate laboratory personnel as soon as possible If microbial DNA analysis is expected, freeze the sample immediately (-60 to -80 C is recommended) and contact the appropriate laboratory personnel as soon as possible Thorough evaluation of soil or geological evidence requires an understanding of the origin and context of the individual samples. Close coordination with the laboratory receiving the evidence is highly advised to ensure that all needed information and samples are made available to the personnel conducting the examinations. Therefore, the following information should be provided whenever possible Scene information and documentation:

17 Photographs of the scene and evidence Sketches (with cardinal directions) noting the location of evidentiary items and collected samples Notation of the exact location of the collection site, including GPS coordinates or equivalent, if available Slope and indications of topography (flat terrace, mountain side, etc.) Local maps Individual sample information and documentation: Unique sample identifier (e.g. case number and item number) The date and time of collection The name of the individual who collected the sample Precise location of the sample collection and the depth from the surface (e.g. surface, 6 inches below the surface) at which the sample was collected Description of the location from which the sample was collected (e.g. ditch, front left tire well) 6. Keywords 6.1 soil; geological materials; forensic analysis; collection methods; evidence; dust; soil sampling; horizon; ped; texture; soil structure; soil color