Download History of Forensic Geology

Using Dirt to Solve Crimes
 Search for the:
»the link between earthen materials
that have been transferred to other
objects or locations.
»possible origin or sources of the
earthen material.
 1887–1893 Sir Arthur Conan Doyle
 Sherlock Holmes used composition of
soil and mud samples to help link an
individual to a specific location where
a crime had been committed.
 This was not a practice used by police
of that time.
 1893 Hans Gross, a Austrian criminal
investigator
 wrote in his book Criminal Investigation
» there should be a study of “dust, dirt on shoes
and spots on cloth.”
» “Dirt on shoes can often tell us more about
where the wearer of those shoes had last been
than toilsome inquiries.”
 Murder case in 1904 was the first use of
soil evidence to solve a crime.
 A seamstress named Eva Disch was
strangled by Karl Laubach.
 Georg Popp, a German forensic scientist
linked soil evidence from Laubach’s pants
to a handkerchief left at the crime scene.
 WWII – Japanese balloon bombs
» American geologist determined that the sand in the
counterweights came from a particular beach in
Japan.
» http://www.youtube.com/watch?v=_NlyJ4Zbld8
» http://www.youtube.com/watch?v=fO6-96Pyi0o
 Cattle rustlers took cattle from Missouri to
Montana.
»Analysis of the cow manure revealed fragments
of rock made of silica which was a rock only
found in Missouri.
 Upper layer of earth that is capable of
supporting plant growth
 Soil is formed from the weathering of
rocks and minerals
 Also contains:
» Minerals
» Decaying organisms
» Water
» Air
 Parent material
» type of rock minerals
present
 Climate
» Temperature
» Rainfall
» Wind
 Topography
» Slope of Landscape
 Biological Factors
» Plants
» Animals,
» Micro-organisms
» Human interaction
 Time
» “old” soil vs. “new” soil
» Soil composition over
time
 Physical Properties
»
»
»
»
»
»
»
Density
Magnetism
Particle size
Mineral content
Color
Conductivity
Heat Capacity
 Chemical Properties
» pH
» elements present
•
•
•
•
Nitrogen
Phosphorous
Potassium
Calcium
Soil is identified based
on particle size as
one of three
classifications:
1. Sand 0.05 to 2.00 mm
2. Silt –
0.002 to 0.05 mm
3. Clay –
less than 0.002 mm
 Classified by texture which is the result
of how much of each type of soil (sand,
silt, and clay) is present .
 Classifications are typically named for
the most abundant particle size or a
combination of the most abundant
particles sizes
• Ex: "sandy clay" or "silty clay."
 A fourth term, loam, is used to describe
a combination of sand, silt, and clay.
 Soil is considered Class Evidence
 Evidential value of soil can be excellent
because:
» Types of earth material are virtually unlimited.
» Have a wide distribution and change over short
distances.
» The statistical probability of a given sample having
properties the same as another is very small
 Value increases if it contains:
Rare or unusual minerals
Rocks
Fossils
Manufactured particles
 More than 2,000 minerals have been identified.
 Twenty or so are commonly found in soils;
most soil samples contain only three to five.
 Forensic Scientist will analyze the physical
and chemical characteristics of the soil
such as :
» Size
» Shape
» Color
» Mineral content
» Organic material content
» pH
 X-ray diffraction is a specific technique used to
determine the mineral composition of the soil
» Soil sample is crushed into a fine powder which is then
tested
» X-ray is deflected off the powder and produces a
pattern on film
» Each mineral and chemical produces a specific pattern
 Electron microscope can be used to identify
particles