Soil Evidence

Question 1

Why is soil a valuable piece of trace evidence?

Answer 1

-soil is found everywhere
-soils from different locations

Question 2

Who were three forensic investigators (both real and fictional) that utilized soil evidence?

Answer 2

-sir Arthur Conan Doyle (sherlock Holmes)
-Dr. Hans Gross
-Georg Popp

Question 3

what are five ways soil science is used today in forensic science?

Answer 3

– 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

Question 4

what is soil?

Answer 4

a mixture of weathered rock, microorganisms, decaying organic matter, water, and air.

Question 5

what is an example of physical weathering?

Answer 5

boulders becoming smaller rocks, and plants splitting the earth with their roots

Question 6

what is an example of chemical weathering?

Answer 6

(mineral content

Question 7

what is three main soil textures based on granule size?

Answer 7

– Sand (coarse), Silt (medium), and Clay (fine)

Question 8

Why do forensic scientists compare the percentages of sand, silt, and clay in soil
samples from a crime scene?

Answer 8

to see if it’s consistent.

Question 9

What is sediment?

Answer 9

sand, silt, or clay disposed by wind or water

Question 10

What is a soil profile? Describe three of the layers.

Answer 10

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

Question 11

What happens to the soil when a body decomposes?

Answer 11

chemical products seep out of the decomposing body and into the soil, changing the soil chemistry

Question 12

What are cadaver decomposition islands?

Answer 12

formed by the decomposition products that initially kill vegetation

Question 13

Why do bodies in a shallow grave decompose differently in a shallow grave than a deep grave?

Answer 13

Bodies buried shallow will attract more activity from animals and will decompose differently

Question 14

What happens to bodies decomposing in:
a. Wet/high moisture areas?
b. Dry/low moisture areas?
c. Low oxygen areas?

Answer 14

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

Question 15

What is the difference between sands made from fragments and sands made
from crystals?

Answer 15

Fragment: contains more than one mineral
Crystal: contains one type of mineral

Question 15

What are the four main types of sand? What is the source for each type of sand?

Answer 15

– 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

Question 16

What affects the color of sand?

Answer 16

Color depends on type of mineral
* Quartz (most common)
* Feldspar
* Mica
* Iron

Question 17

What does microscopic analysis of soil tell investigators?

Answer 17

Provides information about the origin of the soil

Question 17

What is the procedure (4 steps) for collecting and documenting soil evidence?

Answer 17

1. Document, photograph, and sketch scene of crime for site
   evidence forms.
2. Evidence collector gathers at least 4 tablespoons of material.
   3.Collect samples beyond the crime scene.
3. Document, package, and label all samples.

Question 18

What are three ways to spot a potential gravesite?

Answer 18

– Digging a grave alters soil profiles
– Distinguishing natural from disturbed areas
– Detecting sites is easier from the air or a hilltop

Question 19

What are three chemical analysis tests that could be run on soil?

Answer 19

Determining moisture content, pH value, and mineral composition

Question 20

What are three biological analysis tests that could be run on soil?

Answer 20

DNA analysis for specific target
sequences, Indicates the
presence of a particular microbe, and Requires a sample of just 200 mcg

Question 21

What is the sand: silt: clay ratio for loam? (you can also write percentages).

Question 22

Name the four elements/nutrients that we talked about that affects the pH of the
soil.