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.
| Becoming
a forensic geologist For students interested in taking a class in forensic geology or entering the field, the pickings are slim. Only a few colleges in the United States offer forensic classes specific to geology, partly because, as one professor puts it, "it's pretty hard to teach geology 101 in an hour." With the recent surging popularity of forensic science TV shows, however, forensic geology classes are becoming more readily available. Forensic scientists must have a wide breadth of scientific knowledge as well as a firm grasp of microscopy, so forensic geologists suggest that students take classes in all the sciences as well as criminal justice classes. More specifically, suggests Wayne Isphording, a forensic geologist and geology professor at the University of South Alabama, students who are interested in becoming forensic scientists should take classes in physics, chemistry (especially analytical or instrumental chemistry), biology, math, multivariate statistics and of course, he says, a lot of geology. Isphording has spent the last 39 years teaching a plethora of different geology classes while also working as a forensic geologist on many criminal and civil cases, including a recent groundwater pollution case where the offender was identified by forensic analysis. Last fall marked the first time that Isphording taught a forensic geology class — prior to that, he had simply included forensics in his geoscience courses. Over the years, in his hydrology, optical mineralogy and geochemistry classes, among others, Isphording has taught "the practical side" of the science, always bringing into the classroom cases he has worked on so that "students see how the science applies" in the field. And this, he says, is the way to get a student truly interested in the coursework. Jack Crelling, a petrologist and forensic geology professor at Southern Illinois University in Carbondale, agrees that bringing in specific forensic cases is the best way to gain a student's interest. He starts each semester with real-life cases involving the geoscience topics he'll cover in the course, involving everything from rock and mineral characterization, to sand and soil analysis, amber identification and diatom analysis. The primary objectives of his course, he says, are to get the students to develop the skills to "critically observe, and to teach a little geology too." Crelling also teaches students a bit about evidence collection, courtroom testimony and ethical issues, and introduces students to some of the technologies used by the forensic geologist: scanning electron micrsocopy, x-ray diffraction, optical microscopy, to name a few. For both Crelling and Isphording, most of the students that take their forensic geology classes are not geology majors, nor usually even science majors. At Southern Illinois University, the forensic geology class fulfills a general education requirement for nonscience majors. And because of the "coolness factor" of the topic and how popular forensic science is today, Crelling says, he gets a lot of nonscientists taking the class for the requirement. Isphording's class is filled with criminal justice majors, who usually have little if any scientific background. However, both professors say that they break the class down to a very simple level, just teaching the necessary basics of microscopy and geology. For students interested in delving further into the science — and both professors says they've captured several students' interest in geoscience — Crelling and Isphording suggest starting at the very beginning, Geology 101, and progressing into mineralogy and other courses from there. Geochemist Tim Ku's forensic geology course at Wesleyan University in Connecticut is also very popular among nonscientists. In the first semester he offered the course, 11 percent of the student body expressed interest in taking it. He keeps the class small, however, to ensure that everyone has full access to microscopes. Most of the class, he says, is based around microscopy because these instruments, especially polarized light microscopes, "are very useful for everything in the forensic world." Students at most schools can take a lot of heavy science classes, Isphording says, that involve a lot of microscopic use. And that is the best way to prepare for a future in forensic science. Students can always go to a graduate school where they'll learn more specific techniques, and can enter programs such as that offered by the McCrone Research Institute in Chicago, the foremost forensic teaching program in the country, Ku says. Besides learning microscopy, Isphording adds, students just need to get a very broad and strong science background. The more they know, he says, the easier it will be to testify in court and not get "torn to shreds by the attorneys" — something students better be prepared for once they enter the field. Megan Sever Links: McCrone
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