An investigation into
the techniques used to
analyse soil, pollen,
and diatom evidence.
Luke David Farrar
November 2020
, Introduction
The analysis of soil, pollen, and diatom evidence is of crucial importance in a wide range of forensic
investigations. To cover the main techniques, along with the methods of collection for these types of
evidence, will be the focal point of this report.
Results from my tests will be included as supporting evidence, in addition to evaluating and
comparing each test. A discussion and conclusion of multiple results; an evaluation of the techniques used,
along with improvements based on a broad range of different techniques, will be crucial in determining the
methods and practicality of the examination and usefulness of these three forms of evidence.
Soil analysis
Introduction
Using soil sieve analysis, I am aiming to match an unknown sample of soil collected at a crime scene
to 12 controlled samples to place the suspect at the scene. This will be completed by comparing the
characteristics of each soil using the size, colour, and pH to make a positive match.
Hypothesis
Suspect sample A will match control sample 3.
Equipment
Sieves (sizes on table)
Tissue for desk
Containers for soil samples
Munsell colour chart (p. 10R)
pH/UV indicator
Sieve Measurement
Method
no. s
Using six layers of sieves with varying mesh sizes that are stacked
No. 20 0.840mm
on top of each other, place a fistful of a soil sample on the top sieve (No.
No. 30 0.590mm
250). Then, gently shake the sieve tower to allow the soil to pass through
No. 60 0.250mm
the various layers but be careful to not shake the tower too much. Once the
No. 80 0.177mm
soil has travelled through the sieve, dismantle the 6 sieves, and determine
No. 120 0.127mm
the sieve with the highest amount of soil present. This sieve will be used to
No. 250 0.057mm
classify the particle size of the soil, as well as the overall distribution of
particle size.
Use page 10R of the Munsell colour chart to determine the colour of the soil sample. Then, using a
pH indicator, determine the pH of the soil. These data sets will be used to determine which controlled
sample of soil matches a suspect sample.
Techniques
Some of the major identifying features of soils are their structure, sediment, and colour. One
technique to analyse the structure and sedimentation—by using the particle size and distribution of the soil
—is a gradation test, or a soil sieve analysis.
By separating the soil sample through multiple layers of mesh sieves decreasing in size, it is possible
to determine the distribution of an unknown soil sample. As an identification
technique, knowing the distribution and particle size of an unknown sample are
extremely beneficial in determining the origin of the sample. Further analysis can
then be taken by weighing the contents of that sieve against the overall mass of the
soil sample.
The table in (Figure 1.2) shows the measurements used during my soil
analysis. These measurements vary from the example shown in (Figure 1.1),
though, they are set up the same way.
After measurements of the distribution and particle size of soils have been
(Figure 1.1)
completed, the colour of the soil sample is then analysed to increase our confidence
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