Soil Evidence Flashcards
Why is soil a valuable piece of trace evidence?
-soil is found everywhere
-soils from different locations
Who were three forensic investigators (both real and fictional) that utilized soil evidence?
-sir Arthur Conan Doyle (sherlock Holmes)
-Dr. Hans Gross
-Georg Popp
what are five ways soil science is used today in forensic science?
– Investigating burial sites
– Tracking the origin of drugs
– Estimating postmortem intervals (PMI) using microbes in the soil
– Tracking human movement with cadaver dogs
– Locating bodies using chemical scents in the soil
what is soil?
a mixture of weathered rock, microorganisms, decaying organic matter, water, and air.
what is an example of physical weathering?
boulders becoming smaller rocks, and plants splitting the earth with their roots
what is an example of chemical weathering?
(mineral content
what is three main soil textures based on granule size?
– Sand (coarse), Silt (medium), and Clay (fine)
Why do forensic scientists compare the percentages of sand, silt, and clay in soil
samples from a crime scene?
to see if it’s consistent.
What is sediment?
sand, silt, or clay disposed by wind or water
What is a soil profile? Describe three of the layers.
Geographic areas have unique sequences of layers.
-humus: decaying organic matter
-topsoil: Dark; mixture of humus and minerals; plants sprout here
-sand and slit: light; water leaches away most minerals
What happens to the soil when a body decomposes?
chemical products seep out of the decomposing body and into the soil, changing the soil chemistry
What are cadaver decomposition islands?
formed by the decomposition products that initially kill vegetation
Why do bodies in a shallow grave decompose differently in a shallow grave than a deep grave?
Bodies buried shallow will attract more activity from animals and will decompose differently
What happens to bodies decomposing in:
a. Wet/high moisture areas?
b. Dry/low moisture areas?
c. Low oxygen areas?
A. Body can produce waxy substance under high moisture conditions
B.Better drainage (dry area) = mummification
c. Low oxygen makes bodies stink even more; can attract cadaver dogs
What is the difference between sands made from fragments and sands made
from crystals?
Fragment: contains more than one mineral
Crystal: contains one type of mineral
What are the four main types of sand? What is the source for each type of sand?
– Continental sand
* Results from weathering of continental rock
– Volcanic sand comes from volcanoes
– Skeletal, or biogenic sand
* Remains of marine organisms
– Precipitate sand
* Forms from minerals coming out of a water solution
What affects the color of sand?
Color depends on type of mineral
* Quartz (most common)
* Feldspar
* Mica
* Iron
What does microscopic analysis of soil tell investigators?
Provides information about the origin of the soil
What is the procedure (4 steps) for collecting and documenting soil evidence?
- Document, photograph, and sketch scene of crime for site
evidence forms. - Evidence collector gathers at least 4 tablespoons of material.
3.Collect samples beyond the crime scene. - Document, package, and label all samples.
What are three ways to spot a potential gravesite?
– Digging a grave alters soil profiles
– Distinguishing natural from disturbed areas
– Detecting sites is easier from the air or a hilltop
What are three chemical analysis tests that could be run on soil?
Determining moisture content, pH value, and mineral composition
What are three biological analysis tests that could be run on soil?
DNA analysis for specific target
sequences, Indicates the
presence of a particular microbe, and Requires a sample of just 200 mcg
What is the sand: silt: clay ratio for loam? (you can also write percentages).
Name the four elements/nutrients that we talked about that affects the pH of the
soil.
