As with so many other types of criminal investigation, forensic geology began with the writings of Sir Arthur Conan Doyle, who wrote the Sherlock Holmes series between 1887 and 1893. He was a physician who apparently had two motives: writing salable literature and using his scientific expertise to encourage the use of science as evidence.

In 1893, Hans Gross, an Austrian forensic scientist, wrote the book Handbook for Examining Magistrates, in which he suggested that perhaps the dirt on someone's shoes could tell more about where a person had last been than toilsome inquiries.

It was only a matter of time before these ideas from an author of fiction and criminalists' handbook would appear in a courtroom.

A century later, the use of geologic materials in criminal and civil cases is commonplace. Public and private laboratories for analyzing soils and related materials include the FBI laboratory in the United States, the Central Research Establishment in Great Britain, the Centre of Forensic Sciences in Toronto, the National Institute of Police Science in Japan and many others.

Forensic geology studies vary in scope. A common type of investigation involves identifying a material that is key to a case — for example, examining pigments in a painted picture or material in a sculpture when authenticity or value is at issue. Identification is also important in questions of mining, mineral or gem fraud to determine if the material is what its sellers claim it to be (see story). And identification of fire-resistant safe insulation on a person or individual's property may provide probable cause for further investigation.

Beyond identification, forensic geologists can also look at the origin of particular material. Here the examiner needs a broad knowledge of the geology and the best geologic and soil maps to answer questions. For example, if the soil on a body does not match the location where the body is found, from where was the body moved? Similarly, examiners can compare two samples, one associated with the suspect and the other collected from the crime scene, to see if they had a common source: Does the soil on the suspect's shoe compare with the soil type collected at the crime scene, for example?

Another new developing area of forensic geology is its use in intelligence work. A person, for example, may claim to have never been to a particular location, but is then found with rocks from that spot, thus linking the individual to a geographic location. Remember the outcrop you saw behind Osama bin Laden on TV after September 11. What was the location? A geologist who has done field work in the area would be able to locate that outcrop, and that actually happened: Geologist John Shroder was able to identify the region where bin Laden had been sighted in Afghanistan in 2001 (see Geotimes, February 2002).

Geologic evidence rarely provides a unique solution for which the geologic mind cannot imagine another possibility. But there are some exceptions, as illustrated by the following two cases.

Murder and the pond

The murder of John Bruce Dodson produced one of the most interesting cases in the entire history of forensic geology. Here, the geologic evidence is unequivocal in that it tied the suspect directly to the crime and eliminated the suspect's alibi. Most importantly, the investigator of the crime recognized the potential importance of the geologic evidence and arranged for the examination of that evidence. The testimony of the forensic geologist was critical to the prosecution of the case.

A pond lined with bentonite in the Uncompahgre Mountains of western Colorado revealed key geologic evidence that incriminated Janice Dodson in the murder of her husband, John Bruce Dodson. Courtesy of Bill Booth.

The case began on Oct. 15, 1995, when John Dodson was found dead while on a hunting trip with his wife of three months, Janice. The scene was a crisp autumn morning high in the Uncompahgre Mountains of western Colorado.

At first glance, it appeared to be a hunting accident. However, the autopsy revealed two bullet wounds to the body and one bullet hole through John's orange vest. Western Colorado District Attorney Frank Daniels points out in his book on the case, Dead Center, that if there had been only one bullet, there never would have been an investigation and the death would have been ruled an accident.

The investigation showed that the Dodsons were camped near other hunters, one of whom was a Texas law enforcement officer. He responded to Janice's frantic call that her husband had been shot. She was standing about 200 yards from the camp in a grassy field along a fence line. The officer determined that John was dead and started the process of getting help.

Prior to calling for help, Janice had returned to her camp and removed her hunting coveralls, which were covered with mud from the knees down. She later told investigators that she had stepped into a mud bog along the fence near camp. Investigators found a .308-caliber shell case approximately 60 yards from the body. In addition, they found a .308-caliber bullet in the ground on the other side of the fence, which created a direct line from the location of the case to the body to the bullet.

Janice's ex-husband, J.C. Lee, was also camped three-quarters of a mile from the Dodsons. Janice knew the site was his favorite camp location. He naturally came under suspicion. However, Lee was hunting far away from camp with his boss at the time of the shooting. Most importantly, Lee reported to investigators that while he was out hunting, someone had stolen his .308 rifle and a box of .308 cartridges from his tent.

Winter comes early at 9,000 feet in the Umcompahgre, and little more could be done at the scene. However, investigators Bill Booth, Dave Martinez and Wayne Bryant returned during the summers of 1996, 1997 and 1998 and searched for the rifle and other evidence. They tried to search every place a weapon could have been hidden. They combed the entire area, including ponds, with metal detectors in hope of finding the rifle; it has never been found.

During the final search of the pond near Janice's ex-husband's camp, Al Bieber of NecroSearch International (a nonprofit consulting company for law enforcement agencies) commented that the mud in and around a cattle pond near Lee’s camp was bentonite, a clay that someone brought to the pond to stop the water from seeping out of the bottom. That evening, Booth and Martinez were camped near the crime scene. They were discussing the evidence in the case when investigator Booth said, "The mud." He was referring to the dried mud that was found on Janice Dodson's clothing. If Janice had obtained the rifle from Lee's camp, she would most likely have stepped or fallen into the bentonite clay that drained across the road from the cattle pond.

Remembering Janice’s statement that she was returning to camp on the morning of the crime and stepped into a mud bog near her camp, Booth and Martinez decided they needed to obtain dried mud samples from the bog near the Dodsons' camp, the area around a pond nearby the camp, and the human-made pond and runoff near Lee's camp.

Booth and Martinez packaged the dried mud from each location and sent the samples along with the dried mud that had been recovered from Janice’s overalls to the laboratory section of the Colorado Bureau of Investigation in Denver, where it was examined by Jacqueline Battles, a forensic scientist and lab agent.

Battles is a highly respected forensic scientist with considerable geologic training, who, like many of the others in the profession, got her early training with Walter McCrone. She concluded and later testified to the fact that the dried mud found on Janice Dodson's clothing was consistent with the dried mud recovered from the pond near Lee's camp. The dried mud that had been recovered from Janice's overalls was found not to be consistent with the mud bog or the pond near her camp. This was a breaking point in the case that allowed Booth and Martinez to put Janice Dodson in her ex-husband's camp around the time his rifle had been stolen. There are no other bentonite-lined ponds in the area and no bentonite deposits.

Booth and Martinez went to Texas and served an arrest warrant on Janice. She was extradited to Colorado, tried in court and convicted in the murder of John Bruce Dodson. The jury understood the results that followed Booth's insightful "mud" exclamation. Janice is now serving a life sentence without the possibility of parole in Colorado's state prison for women. The mud samples collected from Janice's clothing are still in the sheriff's office evidence room, where they have been since 1995.

Slicks and sands

A case that illustrates many of the issues comparing soil and related material occurred in Canada a few years ago. The body of eight-year-old Gupta Rajesh was found alongside a road outside of Scarboro, Ontario. The back of his shirt had a smear of oily material, and the preliminary conclusion was that he was the victim of a hit and run accident, with the oily material coming from the undercarriage of a vehicle. But examination of the oily material and the particles suspended in it by forensic geologist William Graves of the Centre of Forensic Sciences in Toronto told a different story.

Investigators had collected samples of oily material on the floor of an indoor concrete parking garage where a suspect, Sarbjit Minhas, parked her Honda automobile. Analysis of the samples showed that the sand and other particles within the oil from the victim's clothes and the parking garage were similar. Analysis of the oil from the victim's shirt and garage floor showed them to be both similar and different from oil collected on the floor of 10 other garages in the area.

Particles in samples from the victim's clothes and the suspect's parking place provided considerable information. The sand from both samples was sieved, and subsamples produced of the various size grades for the two samples. When compared after the oil had been removed, the color of each pair of subsamples was identical. Additionally, the heavy minerals in both samples were similar, and three distinct kinds of glass were found in the two samples: amber glass, tempered glass and lightbulb glass. Each of the different glasses was identical in refractive index value (the amount a ray of light bends when passing through the glass into another medium). Small particles of yellow paint with attached glass beads were found in both samples. This type of paint is often found on center stripes of highways and reflects light.

Graves concluded that there was a high probability that the body of Gupta Rajesh had been in contact with the concrete floor of the garage at the place where the suspect parked her car. Interestingly, the same oil and particles were found in the suspect's Honda. Whether the oil and particles on the victim came from inside the vehicle or the floor of the garage, the presence and distinctiveness of the samples still strongly associated those two areas with the victim.

Minhas was tried in the Superior Court of the Province of Ontario in November 1983 and convicted, with help from testimony by Graves.

This case illustrates an important concept in the presentation of soil evidence and perhaps all physical evidence, except DNA. We have become awed and impressed by the high probabilities that result from DNA evidence. Some people expect that other types of evidence should have similar statistical information.

But in the Minhas case, we see a conclusion based on at least 10 different materials and observations. Because we do not know the probability of a tempered glass fragment, a particular group of heavy minerals, or sand of the same color being on a particular parking place in a concrete garage in Scarboro, Ontario — and in all likelihood we will never know — a frequency statistic cannot be generated. A useful database of sands, particles, glass, oils and heavy minerals would be too difficult to generate. Additionally, it may not apply to any one specific case because of the variability of mineral particles — the very distinctiveness that makes geologic materials such good evidence.

Thus, we rely on the skilled and honest examiner to reach a conclusion expressed in words rather than in numbers to inform the jury or judge so that they can reach a verdict. In this way, the expert is a teacher, instructing the judge, attorneys and jury in the basic concepts and premises that allow them to do the work they do. The triers of fact must be schooled in the methods of production of the evidence (how light bulb glass is made, for example), the procedures used to analyze it, and what makes the evidence significant. That understanding will lead the courts to an appreciation of unquantifiable evidence and give the jury a basis for weighing its significance.

Geologic evidence will continue to be developed and presented in courtrooms around the world. The quality of evidence collection and examination will improve, and new methods will be developed. The results will be to the benefit of justice.

Geotimes Home | AGI Home | Information Services | Geoscience Education | Public Policy | Programs | Publications | Careers © 2024 American Geological Institute. All rights reserved. Any copying, redistribution or retransmission of any of the contents of this service without the express written consent of the American Geological Institute is expressly prohibited. For all electronic copyright requests, visit: http://www.copyright.com/ccc/do/showConfigurator?WT.mc_id=PubLink