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Forensic Geologists Uncover Evidence
Soil And Water

By Robert A. Hayes, CPG

When I use the word forensics, most people conjure up images of TV doctors like Quincy examining a dead body to solve the crime of the day, or they recall lawyers from programs like "The Practice" who receive "lab results from forensics" that change the focus of their case. But, when I tell them my profession is forensic geology, most people are not sure what to think. My explanation, I must admit, is pretty booorrrrring - until I give them a few examples!

Simply, forensic geology is the scientific application of earth sciences to legal matters. Practically, this means that a forensic geologist identifies, analyzes, and compares earth materials, such as soil, rocks, minerals, and fossils found on or in a receptor (e.g., a suspect, a vehicle or other medium of transfer, such as water) to possible source areas (e.g., a crime scene, an alibi location, and/or a point of disposal/release). The goal of these comparisons is to establish the degree of probability that the material was or was not derived from a particular location; thereby, associating or disassociating a person or object with that location1. In other cases, the comparison of earth materials or changes in materials is used to determine the time an incident occurred, the cause of an incident and/or responsibility for an incident.

I'm sure you recall from your science classes that the earth is composed of igneous, metamorphic, and sedimentary rocks, each with a variety of minerals and/or fossils that originate in specific areas, and that these rocks are often changed and/or re-distributed to other locations by wind, water, biota and/or humans. Overall, because the sizes, types, and distribution of earth materials are so varied, the probability is high that earth material at any location is unique. Therefore, the evidentiary value of earth materials is excellent, in many cases1. This value is further enhanced when other sciences, such as botany, paleontology, biology, and hydrology, provide corroborating evidence.

Unfortunately, some attorneys and investigators don't consider soil (dirt, to some), water, fossils, rocks, or other earth materials (and sometimes manufactured materials) relevant to their cases, let alone important evidence. However, by analyzing a piece of industrial debris or coal, soil particles on shoes and clothing, types and concentrations of chemicals in groundwater, the type of gas in a water supply well or storm drain, type of rock, water chemistry, and/or other earth materials, forensic geologists often can help identify where, when, and/or how incidents occurred and who is responsible.

Conceptually, forensic geology is inherently beneficial to neither the plaintiff nor the defendant; site-specifically, however, it provides evidence for consideration by all parties:

  • Earth material in the form of soil provided strong evidence against a rape suspect when comparison of soil samples on each knee of his pants matched the soil types from the right and left knee impressions at the rape scene.1 In other cases, analyses of soil on clothing have been used to support alibis and show no connection of the suspect to the crime scene.

  • By identifying the nature and extent of groundwater contamination, a forensic geologist determined the time a chemical release contaminated water supplies, thereby identifying, among several insurance policies, the specific insurance policy in effect and providing coverage at the time of release. In another case, a similar analysis plus a chemical degradation analysis showed that contamination in groundwater at a company originated at another property and a different company was responsible for cleanup.

  • By analyzing road maintenance records and techniques used to sample an unpaved road, a forensic geologist provided evidence that eliminated the validity of the opposition's roadway data and skid testing in a motor vehicle accident case. Geologic analyses of roadways in other cases have shown that unpaved roads were improperly constructed and/or improperly maintained.

Recent television programs, such as "Crime Scene Investigators" leads most people to believe that "forensic geology" is some new science that originated in the United States. Well, they are only partly correct. It is a relatively recent science compared to physics and chemistry, but it is not as new as they think, and it did not originate in the United States. 1European authors, such as Englishman, Sir Arthur Conan Doyle, author of the Sherlock Holmes series of novels from 1887 - 1893, and Austrian, Hans Gross, author of the 1893 handbook Criminal Investigation, initially conceptualized forensic geology in their writings.

Later, these literary concepts were put into practice by the director of the Technical Police Laboratory in Lyons, France, Edmond Locard, who, in 1929, set forth one of the fundamental tenants of forensic geology:

"Whenever two objects come into contact, there is always a transfer of material. The methods of detection may not be sensitive enough to demonstrate this, or the decay rate may be so rapid that all evidence of transfer has vanished after a given time. Nonetheless, the transfer has taken place. - Locard's Exchange Principle

As today's high-tech methods of detection become more and more sensitive, the transfer of material is becoming easier to demonstrate. [That was the boring part; it gets better soon!]

Usually, the forensic geologist looks for the unusual in a sample, such as an uncommon mineral, a microfossil, or a chemical1. But, it may be a simple case of just matching soil, rocks, minerals, or fossils with a particular location or landforms with a particular time (i.e., the exchange of materials, as described above by Locard) that provides assistance to investigators and evidence in civil and criminal proceedings. From something as basic as saving time during an investigation and collecting accurate/available information (e.g., "Dirt on shoes can often tell us more about where the wearer of those shoes had last been than toilsome inquiries." - Hans Gross noted in his 1893 handbook1) to more dramatic uses, forensic geology covers a broad spectrum of applications:

Crime Scene Investigation

  • Hit & Run:
    Under-fender dirt/soil deposited on the road at impact with the victim was used to locate the car/driver; also, matching the grease on the victim with the grease under the car provided supporting evidence1.

  • Rape:
    Soil on clothing of a suspected rapist was used to place the suspect at the crime scene and to eliminate the suspect's alibi; small bits of coal in the soil sample from the suspects pant cuffs provided additional evidence when historical aerial photographs showed that coal was stored at the location of the rape1.

  • Murder:
    Soil and other earth materials found on murder victims have been used to determine the location of homicides, especially when the murder occurs in one location and the body is disposed in another location. And, using water-current measurements, forensic geologists have located bodies/objects thrown into water or, conversely, determined where the newly discovered body/object originally entered the water. Also, geologic techniques have been used to locate clandestine graves and buried weapons1.

  • Assault:
    Identifying the type of rocks used as weapons led to the source location of the rocks and helped locate suspects who were subsequently convicted1.

Environmental Evidence

  • Groundwater Contamination:
    By determining the natural characteristics of a contaminated aquifer, the sources of contamination were identified and property owners at the times of release were identified and separated from the subsequent owners who had no responsibility for contamination. Contrarily, a forensic geologist identified multiple parties that caused groundwater contamination where previously only one party was believed to be responsible.

  • Surface Water Impacts:
    Analysis of sediment in a river lead to identification of parties responsible for water pollution and adverse fishery impacts. Soil erosion from construction activities was shown to have caused excessive lake sedimentation.

  • Wetlands:
    Geologic techniques were used to show the time a wetland was illegally drained and filled.

  • Land subsidence:
    Soil and construction material analyses identified the cause of a collapsing roadway.

Subsurface Investigations

  • Locate buried objects:
    Geologists have identified the location of buried objects, such as chemical drums, storage tanks, vehicles, waste disposal trenches, bodies, and weapons.

  • Mineral Resources:
    Soil analyses and geophysical testing was used in several property condemnation cases to determine the value of mineral deposits (e.g., sand and gravel).

Insurance Claims - Accidents / Personal Injury

  • Vehicle Accident:
    Analyzing the composition of a "gravel road" showed how it influenced a vehicle accident.

  • Excavation/Trench Collapse:
    Analysis of site-specific excavation actions and geologic conditions uncovered evidence that determined the party responsible for personal injury resulting from an excavation collapse.

  • Subsurface Explosion:
    Evaluating the possible cause of a sewer tunnel explosion during construction, a forensic geologist showed that the cause was from human activities and that the explosive conditions were known and avoidable prior to construction of the tunnel.

Insurance Claims - Property Damage

  • Vandalism:
    By analyzing the type of rocks thrown at new vehicles being transported on railroad cars passing through several states, a forensic geologist determined the likely location of the repeated vandalism; then, authorities caught the vandals1.

  • Flood Damage:
    Evaluation of groundwater hydraulics showed how retention/detention pond caused increased basement flooding. Also, a forensic geologist provided evidence that showed the extent of property damage resulting from repeated flooding of a county drain that was purposely dammed by a riparian owner to damage another riparian owner up stream. (In addition to property damage, the downstream owner also attempted personal injury by shooting at the upstream neighbor.)

  • Chemical Exposure:
    Based on current chemical concentrations in the soil and groundwater, a forensic geologist calculated the original chemical concentrations to which workers were exposed.

Case Settlement

  • Dispute Resolution / Third-Party Expert:
    By acting as a third-party expert to provide independent technical analysis in disputes/mediation/arbitration/court actions, a forensic geologist has assisted in finding "common ground", win-win solutions, and/or alternative approaches when soil or water is a significant issue.

In the more than 70 years since Locard first formulated his exchange principle, investigators and scientists have applied the principle and other geologic concepts in developing evidence to support many types of court cases. Today, courts in the United States and other countries generally accept forensic geology as a valid source of scientific evidence1.

Just as forensic geology was conceptualized in the minds of writers, its applications may be limited only by our imagination.

1. Murray, R.C., and Tedrow, J. C. F. 1992. Forensic Geology, Upper Saddle River, New Jersey: Prentice Hall.

Robert A. Hayes, CPG is President and Principal Forensic Geologist at GeoForensics, Inc., a forensic geology and environmental consulting firm located in Williamston, MI. He may be reached at 517.655.8348 or by e-mail:

©2000 Geoforensics