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C H A P T E R 13 S O I L A N A LY S I S “Life is hard. Then you die. Then they throw dirt in your face. Then the worms eat you. Be grateful it happens in that order.” —David Gerrold, American Science Fiction Writer OBJECTIVES After reading this chapter, you will understand: • Why soils are class evidence. • When soils can be used as circumstantial evidence. • How to present data mathematically using graphs. You will be able to: • • • • Identify soil’s common constituents. Relate soil type to the environment. Interpret a topographic map. Understand the concept of spectrophotometry and its applications. • Use technology and mathematics to improve investigations and communications. • Identify questions and concepts that guide scientific investigations. • Communicate and defend a scientific argument. SOIL AS EVIDENCE Soil can be important physical evidence at a crime scene because it is everywhere and is easily transferred accidentally. As with other trace evidence, forensic scientists looking at soil compare samples to establish a link or relationship; the more characteristics that can be Body parts of a murder victim, including an ear, were discovered in a marsh. The rest of the body could not be found. Grains of sand from the ear were not endemic to the black mud marsh. Examination of the sand grains showed salt crystals, not enough to imply an ocean beach environment, but perhaps an estuary near the ocean. The nearest such place to the crime scene was searched, and the rest of the body recovered. —abstracted from Forensic Geology 293 KH00006_ch13.indd 293 10/18/05 12:21:49 PM Individual evidence, like fingerprints, can be related to a single source, while class evidence can be associated only with a group of items that share properties or characteristics. matched, the greater the probability of common origin. Comparative analysis uses physical properties such as density, magnetism, and particle size as well as chemical properties such as pH. L A B O R AT O R Y A C T I V I T Y Collecting and Observing Soil Materials soil samples petri dish magnifying glass or stereomicroscope Procedure Georg Popp was a famous forensic investigator in the early 20th century. A farmer, who already had a bad reputation as a poacher, was suspected in a woman’s murder. By a stroke of luck, the suspect’s wife had cleaned his shoes the day before the murder, and he had worn them only one day. Popp noted several individual layers in the thick cake of soil on the bottom of the suspect’s shoes: The first, closest to the sole of the shoe, contained goose droppings, which littered the suspect’s farm. The second layer showed many grains of a red sandstone common to the area of the crime scene. The third layer had a mixture of coal, brick dust, and cement fragments, which were common to ruins where the murderer had hidden his gun. The suspect claimed that on the day of the murder he had walked only in his fields, yet the distinctive field soil of porphyry, milky quartz, and mica was absent in the layers on his shoes. Not only was Popp able to differentiate between locales, but he also established the time sequence of visitation. 1. Bring into school 2 to 4 ounces of soil from around your home. The container should be labeled with your name, the date on which it was collected, and the specific location (such as by front walk, back flower garden, and the like). 2. Put your sample in a labeled petri dish. 3. Describe the sample so that it may be compared to others. Record all observations in your notebook. 4. Observe and describe the soil samples of at least 3 classmates. Based on observations, can soil samples be individualized enough to be used as evidence? 294 Chapter 13 KH00006_ch13.indd 294 10/18/05 12:21:51 PM WHAT IS SOIL? Soil is one of the most common materials in the world. Soil is a complex mixture of different-sized mineral grains from the weathering of rock and organic material from the decay of vegetation and animals. The proportion of sand, silt, clay, and organic matter determines a soil’s properties. For example, at one extreme, there is sand, the result of chemical and physical weathering. At the other end, slow anaerobic decomposition of vegetative matter forms a dark organic soil, such as that found in swamps and bogs. Soil’s composition is different from place to place and is controlled by five important factors: climate, parent material, living organisms, topography, and time. A sample taken a few meters deep may be very different from a sample taken above it. This can also happen when samples are taken a few meters apart; investigators can sometimes use these differences to conclusively prove the common origin of two samples. The forensic definition of soil includes anything mixed in with the soil, such as bits of glass, cinders, asphalt, paint, metal, concrete, bricks, and the like (human-made disintegration products), as well as natural products such as vegetation, seeds, animal matter, spores, and lichens. Often, presence of artifacts makes a soil sample unique to a particular location and provides a link to another sample. For example, soil from either side of a galvanized fence usually contains zinc, dirt below an asphalt shingle roof may show shingle stones, and potting soils often contain slow-release mineral pills. Thus, soil can be important physical evidence at a crime scene; it’s everywhere and is easily transferred (don’t forget Locard’s principle!). For example, samples of soil or mud can link a suspect’s car to clothing, shoes, or other instruments used at a crime scene. As with most forensic physical evidence, comparative tests determine a common origin. “Observation tells me that you have a little reddish mould adhering to your instep. Just opposite the Wigmore Street Office they have taken up the pavement and thrown up some earth, which lies in such a way that it is difficult to avoid treading in it in entering. The earth is of this peculiar reddish tint which is found, as far as I know, nowhere else in the neighbourhood.” —Sherlock Holmes to Dr. Watson, in Arthur Conan Doyle’s The Sign of Four A vertical cross-section of soil shows rather distinct layers called horizons. Thus soil can vary both on the surface as well as with depth. HORIZONS A = topsoil, mostly humus, dark B = clay, some humus, iron oxides C = partially weathered rock Bedrock “When two objects come in contact with each other, material is transferred. The intensity and duration of the contact and the nature of the material determines the extent of the transfer.” —Edmond Locard (1934) Soil Analysis KH00006_ch13.indd 295 295 10/18/05 12:21:51 PM L A B O R AT O R Y A C T I V I T Y A Hit-and-Run Accident A middle-aged male, later identified as Bud Coreopsis, was found dead on the shoulder of Route S98, obviously the victim of a hit-and-run accident. Investigators took samples of soil and fragments of glass from the scene. Police found two likely suspects who could be placed on the highway at the estimated time of the accident. The following dried soil samples were submitted to your crime lab: A. Soil taken from the clothes of the victim B. Soil from the accident site C. Soil scraped from under the right front fender of suspect Blossom Cowslip’s red Citroen D. Soil scraped from under the right front fender of suspect Fescue Snakeroot’s red BMW E. Soil removed from Coreopsis’s yard Materials The word organic refers to substances composed primarily of hydrocarbons; that is, carbon and hydrogen. Conversely, inorganic substances contain a preponderance of elements other than C and H. In soils that would be Si, O, Mg, Al, Fe, Ca, K. glass petri dishes magnet universal pH paper universal pH indicator weighing paper or boat graph paper ruler test tubes Spectronic 20 spectrometer soil samples set of sieves density gradient columns UV light top-loading balance oven stereomicroscopes magnifying glasses Procedure General Appearance 1. Examine each of the soil samples with a magnifying glass or under the stereomicroscope using reflected and transmitted light. Note the presence of unusual material or vegetation such as leaves, roots, pine needles, hair, metal specks, fibers, building materials, trash, or the like. Such objects can provide valuable clues. Record your observations. A fluorescent material absorbs light of a shorter wavelength (often in the ultraviolet) and emits light of a longer wavelength (often in the visible part of the spectrum). 2. Direct ultraviolet light on the soil samples. Note what particles, if any, fluoresce. Certain minerals fluoresce (e.g., fluorite, some calcites, willemite) as well as many manufactured articles such as fibers and plastics. Record your observations. 296 Chapter 13 KH00006_ch13.indd 296 10/18/05 12:21:52 PM 3. Pass a magnet through the soil samples to collect and identify any iron objects. Record your observations. Color 4. The color of a soil is generally related to the presence of particular minerals or organic matter. For example, red soils tend to have highly oxidized iron (that is, rust); black soils tend to contain organic matter, or humus. Wet soil is usually darker than dry soil. The soil must be dried (usually at 100°C for an hour) before making color comparisons. Your samples have been dried already. Select a paint color panel that most closely matches the color of the soil sample. Use it in your report. Acidity 5. Certain soils may be especially acidic or basic. Those high in limestone (CaCO3), for example, will be basic. Soils containing sulfides (S⫺2) and sulfates (SO4⫺2) are usually acidic. Measure the pH by placing a small amount of sample in a test tube, add about a centimeter of distilled water, shake, let the mixture settle, note any discoloration of the water, then add a drop of universal pH indicator. Compare to a color chart, and record the pH. Sometimes you can identify acidic or basic grains by pressing wet universal pH paper against the soil. Look for dots of color under magnification and match to the pH color index. Record your observations. There are an estimated 1,100 distinguishable soil colors. Instead of using paint panels, soil scientists use a book of color chips called The Munsell Soil Color Charts to describe the color of soil samples. humus: the organic part of soil. Soils high in humus are dark colored and usually form either under prairie grasses or in wet locations, such as bogs and marshes, where lack of oxygen slows decomposition of the organic matter. The acidity of a solution is described by pH, a number that represents the hydrogen ion concentration in a solution: pH = ⫺log[H+] Particle Size 6. The composition of soil determines not only its color, but also the range of particle sizes (texture). If the samples come from the same source, then they should have the same range of particle sizes. Arrange the set of sieves in order with the largest holes (the smallest screen number) on the top and the finest screen at the bottom. Screen numbers of 20, 40, and 100 work well. Loam is a medium-textured soil of sand, silt, and clay, as well as organic matter. Loamy soils are best for gardens. An average soil is 45 percent minerals, 25 percent water, 25 percent air, and 5 percent organic matter. Table 1: Grain Size Scale mm 3.35 2.00 0.850 0.425 0.250 0.150 0.075 0.038 0.002 Sieve series, No. 6 10 20 40 60 100 200 400 Texture gravel very coarse coarse medium medium fine fine very fine Stealing saguaro cactus in Arizona and the very expensive cyclads in California has become a very lucrative business. Bills of sale are easy to come by, so the soil on the root systems is the only physical evidence. sand silt clay Below 0.1 mm, dimensions can be expressed in microns or micrometers: 1 mm = 1,000 microns = 1,000 m Soil Analysis KH00006_ch13.indd 297 297 10/18/05 12:21:52 PM Soil scientists have identified more than 70,000 kinds of soil in the United States. 7. Weigh between 5 and 10 g of dried sample and add to the top sieve. Rub your finger over it to break up any large lumps. Put the cover and bottom base on the set of sieves and shake for a few minutes. Tap the sides, remove the cover, and weigh the contents of each sieve. 8. What is the best way you can present your data for comparison to the other samples? Label and save each fraction of soil for later use. See the accompanying table for typical grain sizes of different types of soil. Density Specific gravity is the ratio of the density of a substance to that of water. density: mass per unit volume 9. About 400 years ago, Galileo discovered that a ball of wax could be suspended between a layer of salt water and a layer of fresh water: Objects seek the level of their density. This principle will be used to classify compare soil types. The particles making up soils vary in density as well as in particle size. If two soils are from the same location, they should contain particles of similar densities. Determine the density distribution of the particles by adding soil to a tube containing layers of different-density liquids. Each particle will “float” at an equidensity point in the column, providing a density profile of the soil sample. 10. Use density gradient columns for this part of the activity. Your teacher has made these by layering various proportions of xylene (d = 0.88 g/cc) and bromoform (d = 2.89 g/cc). 11. For each soil sample, weigh onto weighing paper or into a weighing boat 0.1 g of the dried soil fraction that has passed through the 20 mesh screen and remains on the 40 mesh sieve. Typical soil density profiles 12. Carefully pour it into a labeled density gradient column. Do not jostle the column. Within hours, the individual particles of the soils will settle to their density levels. Particle size will have no influence on the density level, just on how fast they settle. Why? Quartz (SiO2) is a common constituent of many soils. Pure quartz is called silica and has a density of 2.65 g/cc, which is very close to the density of bromoform. Organic matter, on the other hand, has a density of less than 1.00 g/cc. Where would you expect to find each of these components in a density column? 13. Draw a soil density profile of all the samples and comment on the differences. 298 Chapter 13 KH00006_ch13.indd 298 3/3/06 3:44:14 AM Rate of Settling 14. This method measures how rapidly a homogeneous sample of soil settles in water. The finer and lighter the particles, the longer it will take them to settle, that is, for the suspension to clear. The amount of light transmitted through the sample can be measured as a function of time through the procedure of spectroscopy by using a spectrophotometer. spectroscopy: the branch of science that involves the study of electromagnetic radiation and its interaction with matter spectrophotometer: a device for measuring the interaction of light with matter You will use a Spectronic 20 for this experiment. This instrument measures the amount of a particular wavelength of light absorbed by or transmitted through a sample. In this case you will measure only the amount of light transmitted through the sample of soil with time after dispersing it by shaking it in water. Sand settles faster than silt, and silt settles faster than clay. See the table on page 297. Decide how best to do the experiment and to present this type of data. Soil Analysis KH00006_ch13.indd 299 299 10/18/05 12:21:53 PM Questions Probative value is the ability of evidence to prove something that is relevant to the crime. 1. Whose car killed Bud Coreopsis? What evidence of probative value do you have? Explain. 2. Do you have enough evidence to convict? 3. What more could be done to tighten the case? 300 Chapter 13 KH00006_ch13.indd 300 10/18/05 12:21:54 PM L A B O R AT O R Y A C T I V I T Y Where Is Alice Springs? On Thursday, July 18 at 9:38 AM, the Springdale County Police received a call from a Mrs. Marshall, who was concerned about the whereabouts of her friend, Alice Springs. Marshall was to have had lunch with Alice the day before, but she never showed up. Marshall called Alice’s house, but there was no answer. That evening, she called again. Mr. Springs curtly told her that Alice’s mother was ill, so Alice had gone to Florida to visit her. Marshall felt that it not like Alice just to leave without telling her best friend. The next morning, Marshall called their hairdresser because she knew Alice had an early morning appointment. Alice had not appeared and had not called to cancel. This prompted Marshall to call the police. The county police had received over the years a number of domestic violence complaints about Alice and Rusty Springs. Indeed, Alice had appeared bruised and cut on several occasions. However, charges were never pressed. The police stopped by the Springses’ house in Martinsville that evening. Rusty Springs brusquely repeated that his wife had left Wednesday to visit her sick mother in Florida, and he didn’t know when she would be back. On Saturday, July 20 at 11:41 AM, after hours of searching, Detective Chernozem found Alice’s mother’s phone number in Orlando and called her. She said that Alice was not there and that she was quite well, thank you! A call to the county seat produced a search warrant, and that evening Detective Chernozem and a colleague descended on the Springs home. A thorough search turned up nothing out of the ordinary. There were several shotguns (Mr. Springs was a duck hunter), but none had been fired recently. As they were leaving through the garage, Detective Chernozem noted a shovel (Figure 1) leaning against the wall next to a pair of black, knee-high rubber boots. What had caught his attention was a dark, puddlelike stain on the garage floor emanating from the blade of the shovel. Looking more closely, he noted a small amount of dark soil under the foot ridge of the shovel. He asked Rusty, who had been dogging them ever since they set foot on his property, if he had been digging recently. Rusty remarked that he had been working in the garden in the backyard. The detective went out back looking for freshly spaded ground. Finding none, he nevertheless took a sample of soil from the garden. Back in the garage, he collected a small amount of dark soil from the back of Rusty’s pickup truck. On a whim, he peered at the underside of the rear left fender of the truck and saw a coating of dirt (Figure 2), which he carefully dislodged with his penknife. It was damp, so it peeled off as a layer. It looked rather like fudge with a dusting of light brown sugar. He observed the same coatings above the other tires, but not on Mrs. Springs’s old Cavalier. Rusty testily denied driving anywhere in the last week other than to work, the bar, and the grocery store. Detective Cherozem impounded the shovel as they finally departed. Consider this episode in light of Alice Springs’s disappearance. Develop a hypothesis of what could have happened. What are the clues? Should Detective Chernozem have done more while he had access to Springses’ house? DNA PAY DIRT Scientists are investigating soil for genetic information new to science that may result in a new antibiotic or other lifesaving medicine. The resource being tapped into is microbial DNA, with genetic instructions for microbe-made chemicals—antibiotics, insecticides, anticancer drugs, antiparasitic agents, and others—that now can only be imagined. “If there are all these different kinds of bacteria, there must be all kinds of chemicals that they’re making,” says Jo Handelsman, professor of plant pathology and a leader of the project aimed at creating vast libraries of new genetic information from the soil. Indeed, soil microbes, scientists know, live in close relationships with other organisms in the same niche, and they almost certainly depend on the chemicals they make for everything from defense to communication. The simple fact that most soil microbes cannot be cultured and studied in the laboratory has prompted researchers to embark on a quest to harvest the hidden potential of soil microbes and the chemicals they make. The promise of this genetic find is great. The relatively few soil microbes that can be grown in the lab have already yielded a host of helpful products, from critical antibiotics and anticancer drugs to antifungal compounds and herbicides. —(University of Wisconsin, Madison) Figure 1 The shovel Soil Analysis KH00006_ch13.indd 301 301 10/18/05 12:21:54 PM Fender Dark soil layer Lighter soil layer Figure 2 Dirt encrustation Detective Chernozem collected five samples: A. soil from the Springses’ garden Earthworms digest organic matter, recycle nutrients, and make the surface soil richer. One earthworm can digest 36 tons of soil in one year! Just how big a pile of soil is that? B. soil from the shovel in the garage C. soil from the bed of the truck D1. the thicker, dark layer of soil from under the truck’s fender D2. the lighter, thin layer coating the dark layer from under the truck’s fender Now, using forensic soil analysis techniques, characterize each sample. What conclusions can you draw from your results? Are your results consistent with your original hypothesis of what may have happened? Are all the dark soil samples the same? Suggest a hypothetical reenactment of disposal of the body. Using the map on page 303 draw up explicit directions so the police know where to look, and quickly, because the predicted rain may destroy vital clues. Through your rapid, astute, deductive reasoning, Detective Chernozem and several colleagues are dispatched to the Mount Horeb swamp road, where indeed there is an apparent blind spot running from the road to the creek. The police notice a tire track in the dark muck by the road but no footprints. After 15 minutes of traversing an area of cattails and saw grass, they find disturbed soil on a slight rise by an old duck blind. They soon unearth the body of Alice Springs, wrapped in a wool blanket. They take a sample of the dark soil, as well as a sample from the dirt road leading into the area. A plaster cast is made of the tire impression. (Did Detective Chernozem check the tires of the truck?) The swamp soil can now be compared to the dark-colored samples from the Springses’ house that you have already charactarized. The sample from the dirt road can be compared to the “light brown sugar” coating of the dark soil from under the fender of Rusty Springs’s truck. Each crime investigation team should submit a report with diagrams, maps, and lab data that can be used in the prosecution of Rusty Springs for the murder of his wife, Alice Springs. Each conclusion must be supported to withstand any cross-examination by the defense. 302 Chapter 13 KH00006_ch13.indd 302 10/18/05 12:21:55 PM Figure 3 Topographic map of the Martinsville-Mount Horeb area Soil Analysis KH00006_ch13.indd 303 303 3/3/06 3:04:37 AM Elevation, feet Figure 4 The Mount Horeb swamp 460 440 420 400 stream swamp road house road stream Figure 5 Possible topographic profile, running SW to NE, near a line of sight; vertical scale exaggerated 304 Chapter 13 KH00006_ch13.indd 304 10/18/05 12:21:57 PM The Coors Kidnapping Q CASE STUDY Adolph Coors III, chairman of the Coors Brewing Company, was kidnapped in the winter of 1960. Joseph Corbett, Jr., alias Walter Osborne, had driven along the dirt road to Coors’s ranch in the Rocky Mountains of Colorado. At a bridge over a creek, he stopped Coors on his way to work and forced him into his yellow Mercury sedan. There apparently was a struggle, and Coors was fatally wounded. Osborne’s burned-out car was found eight days later near a municipal dump on the New Jersey shore. Incredible detective work by the FBI established Osborne’s identity and compiled circumstantial evidence through paper trails. Coors’s body was found about seven months after the kidnapping at a dump high in the Rockies. A few weeks later, Osborne was found and arrested; however, he remained silent. Nevertheless, Osborne had left a record of his travels on the underside of his car. Dust and grit from the dirt roads Osborne had traveled were used to place him in the vicinity of the Coors ranch, the area of the dump where the body was found, and the dump in New Jersey. The inner three layers of dirt taken from under Osborne’s car were compared to 421 samples of soil from areas of Colorado alone to make a match. Ultimately, the geological description and the sequence of the dirt layers were the key evidence in reconstructing the crime and convicting Osborne (see Figure 6). Rocky Mountains Pink feldspar dust from granite Coors Ranch area Light gray quartzose, angular sands from sandstone, shale clay, limestone Near dump where body found Pink feldspar dust grading to coarser and brighter Atlantic City dump, New Jersey Rounded sand grains, silt, cinders, slag, paper fibers, glass wool Figure 6 Sequence of soil profiles of unpaved roads from Osborne’s car Soil Analysis 305 KH00006_ch13.indd 305 10/18/05 12:21:59 PM ASSESSMENT 1 Consider what indicators might place soil near the following: a. b. c. d. e. In forensic science analyses, a sample designated K is the known and originates from a verifiable source. It is also termed exemplar. The questioned or unknown (sample), designated Q, has been collected from a known location, but it is of unknown origin, initially. a highway a home a commercial building the ocean a garden or farm f. g. h. i. j. a river a gas station a railroad track a forest a volcano 2 Why is sand not as useful as soil as evidence? 3 A burglar entered a house by jimmying open a back window above a flower garden. Muddy footprints were found in the house, on the windowsill, and in the garden below the window. Police apprehended a suspect with muddy shoes. How would you investigate the crime scene and any evidence? Define the exemplars and the questioned material. 4 Glass and sand are composed predominantly of . How could one tell them apart? 5 Would a body decay faster if buried in the A and upper B horizon, or in the lower B and upper C horizon? 6 Taxonomy is the science of classification. A hierarchical organization system arranges items into groups with common properties for use in making comparisons, establishing relationships, and managing and locating data. For example, the Henry-FBI system is used to classify fingerprints; chemistry has many classification systems, the periodic table being the most fundamental; Linnaeus worked out an extensive system of classification for plants and animals. What other systems can you think of? Is there such a classification system for soils? If so, describe it. 306 Chapter 13 KH00006_ch13.indd 306 10/18/05 12:21:59 PM 7 Here is a “back-of-an-envelope calculation”: How many grains of 40-mesh sand are there in one cubic foot of dry beach sand, assuming a 25 percent pore volume? How much would one cubic foot weigh? Would one cubic foot of beach sand 40 to 100 mesh weigh more, the same, or less? Why? Additional Projects 1. What does a forensic environmental scientist do? Is this an important field of forensics? What is its future? Prepare a report with examples of cases, real or hypothetical. See, for example, A. Dallas Wait and Linda L. Clark’s article, “Opportunities in Environmental Forensic Chemistry Analysis,” in Environmental Testing & Analysis, p. 31, July/August 1999. There is actually a scientific journal published entitled Environmental Forensics. See www.aehs.com/journals.htm 2. Write a short crime scenario using sand as evidence. What tests could be performed for comparative analysis? See Jane Justus Frazier’s article, “Sand Studies,” in The Science Teacher, May 1996, p. 14. 3. Sometimes the tools or clothing of a person suspected of breaking into a safe will contain traces of safe insulation. What materials are used for such insulation? How could they be characterized and differentiated? Sand grains, transmitted light Sand grains, reflected light Sand grains, crossed polarizers Soil Analysis 307 KH00006_ch13.indd 307 10/18/05 12:21:59 PM References Books and Articles Loynachan, T. E., K. W. Brown, T. H. Cooper, and M. H. Milford. “Sustaining Our Soils and Society,” American Geological Institute. General information on soils. This pamphlet can be purchased through this site or downloaded directly from www.agiweb.org/pubs/pubdetail. html?item=603601al Lynn, W. C., and M. J. Pearson. “The Color of Soil,” The Science Teacher, May 2000, p. 20. McPhee, J. “The Gravel Page,” The New Yorker, January 29, 1996, pp. 46–90. Cases and detailed geological descriptions. This material is also included in McPhee’s book Irons in the Fire, New York: Farrar, Straus and Giroux, 1997. Meloan, C. E., R. E. James, and J. R. Saferstein. Criminalistics, An Introduction to Forensic Science, Lab Manual (6th ed.). Upper Saddle River, NJ: Prentice-Hall, 1998. Miller, L. S., and A. M. Brown. Criminal Evidence Laboratory Manual; An Introduction to the Crime Laboratory (2nd ed.). Cincinnati, OH: Anderson Publishing Company, 1990. Saferstein, R. Criminalistics: An Introduction to Forensic Science (7th ed.). Upper Saddle River, NJ: Prentice-Hall, 2001. Thorwald, J. Crime and Science. New York: Harcourt, Brace & World, 1966. Detailed cases, with a riveting account of Popp’s use of soil layers on a shoe to solve a 1908 murder, pp. 235–252. Van Burgh, D., E. N. Lyons, and M. Boyington. “Teach with Topographic Maps,” NSTA, Stock No. PBO38X8; 1994. This pamphlet is available from National Science Teachers Association, Arlington VA. Websites soils.ag.uidaho.edu/soilorders; soil taxonomy information www.itc.nl/~rossiter/Docs/FM5-410/FM5-410_Ch4.pdf; good technical definition of soil, how it is formed, and test methods www.geoforensics.com/geoforensics/art-1101a.html; good overview of what a forensic geologist does web.umr.edu/~rogersda/forensic_geology; case histories, including “How geologists unraveled the mystery of Japanese vengeance bombs in World War II” Murray, R.“Devil in the Details, The Science of Forensic Geology,” Geotimes, February 2000, p. 14. Murray, R. C., and J. C. F. Tedrow. Forensic Geology. Upper Saddle River, NJ: Prentice-Hall, 1998. 308 KH00006_ch13.indd 308 10/18/05 12:22:00 PM