Advanced evidence type 3 - geology

Question 1

What does forensic geology cover?

Answer 1

rocks
sediments
soils
minerals
dust
fossils
anthropogenics - concrete, bricks etc

Question 2

What the use of rocks in forensics?

Answer 2

They are encountered in case wrk as weights to sink bodies, in bags containing illicit substances such as firearms in smuggling cases

Question 3

What are the classifications of rock?

Answer 3

igneous
metamorphic
sedimentary

Question 4

Why is sedimentary rock the most important for forensic purposes?

Answer 4

These rocks are formed by the accumulation of sediment in water ad air by the processes of erosion over time to form strata (horizons)
they make up 70% of the earth’s surface which gives us a lot of opportunity to find them as trace
diatomaceous earth - predominantly made of diatoms
highly variable, found in food, cosmetics, medicines, insulating material, pet litter

Question 5

What are sediments?

Answer 5

They are distinct from rock because these particle mixtures come from a variety of sources, transported and deposited by air, water or ice

encompass gravel, sand, silt and clay- differenciated by size

Question 6

What is sand?

Answer 6

Between 0.063mm and 2mm
needs to made up of more than 50% sand
can be found at beaches, sand dunes, construction sites, washing machine filters, bodies, vehicles

Question 6

What is gravel?

Answer 6

Any particle sized between 2mm- 64mm
can be found in drowning victims’s mouths/respiratory tract/clothing/shoes
can also be found stuck to adhesive tape - if they have been moved then this can be an indication as to where they have been dumped

Question 7

What is mud?

Answer 7

mud particles are typically less than 0.063 mm
they can be encountered on clothing/footwear from coastal /river floodplains
mainly silt and clay (with some sand and grovel)
have a sticky character when wet, making it adhere to things
may also contain organic matter (grass, pollen)

Question 8

What are soils and what are they made up of?

Answer 8

extremely heterogenous material which have distinct layers - (horizons/strata)
they are made up of;

non-living - inorganic materials, salt crystals, insect skeletons, fossils
Living - bacteria, algae, fungi, mammals

unusual - cement plaster, metallic fragments, glass, paint flakes, fibres, plastic fragments. MOST USEFUL FOR TRACE EVIDENCE!!!!

Question 9

How is soil useful in forensic trace evidence?

Answer 9

Can help pinpoint a geographical location.
database is the UK soil conservatory
used in the case of the Soham murders (2002)

Question 10

What is the value of dust?

Answer 10

A geological form of trace which can transported thousands of miles
chemical composition varies considerably and is indicative of geographical area
Dust is ubiquitous and can be found everywhere

Question 11

What are anthropognics?

Answer 11

grouped as man made
concrete, bricks, glazed ceramics,
plastic fragments, fibres, glass fragments, metal fragments

Question 12

How is concrete useful in case work?

Answer 12

Case of entombed baby “Lara” in a concrete block in a garage. Cumbria, 2002

Question 13

What is the analytical workflow for soil/geological analysis?

Answer 13

Gross examination, recovery and collection
Preliminary evaluation of physical characteristics (weight and volume, colour and texture, dimensions, surface area, perimeter and shape e.g irregularity)
(Physical fit assessment - cannot be implemented in this case)
All microscopic techniques -Polarised light microscopy
Micro spectrophotometry - colour determination
Measurement of pH and electrical conductivity - GIVES AN INDICATION AS TO WHERE THE SOIL CAME FROM!
Infrared spectroscopy - organic content
Raman spectroscopy - inorganic content and carbon content
SEM/EDX;
SE (surface topology and morphology)
BSE (homogeneity)
XRD - crystal structure, polymorphs
AAS, XRF, NAA, ICP-AES - elemental composition
Isotopic analysis - isotope ratio
Chemo metrics - MVA - most widely used (HCA and PCA)