Lecture 20: Advanced Evidence Types Part 3 Flashcards
1
Q
Forensic Geology
A
- Rocks
- Sediments
- Soils
- Dusts
- Minerals
- Fossils
- Anthropogenic, e.g. concrete, bricks
- Sediments, soils and dusts are mixtures of organic/inorganic particles
2
Q
Inorganic fractions
A
Inorganic fractions include rock fragments, mineral grains and amorphous matter, e.g. volcanic glass.
3
Q
Organic fractions
A
Organic fractions derive from biological processes, e.g. shells and forams (calcite, aragonite), phytoliths (silica), diatoms, or CHO based products (e.g. coal)
4
Q
Rocks
A
- Encountered in casework as weights to sink bodies, in bags containing illicit substances/firearms, as concealment material in smuggling cases, or as projectiles (thrown or catapulted)
- Granite is a form of form
- Gravel is heavy and masks anything inside.
- We can do analysis of the conceal materials to potentially discover where the item being hidden has come from.
5
Q
Three main classifications of rocks
A
Three main classifications:
* Igneous
* Metamorphic
* Sediementary
6
Q
Igneous rocks
A
- Rocks formed from a liquid magma cooled deep in the earth or extruded onto the surface by volcanoes.
- Granite, lava, rhyolite, porphyry, obsidian, pumice
7
Q
Metamorphic type of rock
A
- Rocks formed by varying degrees of heat and pressure of any type of existing rock.
- Gneiss, marble, mica schist, anthracite, slate, quartzite
8
Q
Sedimentary rock
A
- Rocks formed by the accumulation of sediment in water and ait by the processes of erosion, precipitation, evaporation and compaction.
- Best for forensics
- Created overtime as layers are compacted into stratas.
- ~70% of rocks at Earth’s surface
- Diatomaceous earth – diatoms (silica), (alumina) clay minerals, iron oxide. 80-90% silica diatom based.
- They are highly variable and will be found everywhere.
- Food, medicine, cosmetics, insulating, absorbent, pet litter, stabiling component in dynamite. It is found everywhere.
Stabilising component in dynamite! - Conglomerate
- Limestone
- Sandstone
- Travertine
- Shale
- Dolomite
9
Q
Sediments
A
- Particle mixtures from a variety of sources, transported and deposited by air, water or ice which makes them different from rocks.
- Gravel, sand, silt, clay are the 4 different types of sediments.
- Smaller than rocks
- Differentiated by their size
- Gravel then sand then silt then clay.
10
Q
Gravel
A
- Biggest form of sediment
- Encountered in casework in tyre treads, shoe soles, in drowning victim’s mouths/respiratory tract/clothing, or on associated adhesive tapes
- It might give you an indication where someone was dumped if their body was moved.
- Gravel = 2 mm – 64 mm; cobbles = 64 mm – 256 mm; boulders = >256 mm
- Shingle = rounded gravel found in marine and lake environments
- Used in flowerbeds, driveways and other decorative uses.
- Water constantly erodes the surface forming them in lakes and marines.
11
Q
Sand
A
- Encountered in casework involving beaches, sand dunes, and construction sites; found on/in footwear, clothing, vehicles, bodies, washing machine filters and U-bends of sinks and toilets
- Sand grains = 0.063 mm – 2 mm
- For a sediment to be classed as sand it must contain >50% sand grain sized particles
- Many different minerals – rock fragments (lithic grains) – predominantly quartz (silica dioxide)
- Sand is used in the creation in mortar.
12
Q
Mud
A
- Encountered frequently in casework on skin, under fingernails, on clothing/footwear, in/on vehicles; from coastal/river floodplains, fields, and woodlands
- Pretty high chances of finding it
- Any sediment that has a sticky character when wet which is what makes it different to sand.
- This means it clings to items which is good for transfer.
- Mainly silt and clay (with some sand and gravel)
- Mud particles typically = <0.063 mm
- Many samples also contain organic matter
- Grass, weeds, pollen, etc
- Silt and clay form mud
13
Q
Soils
A
- Unconsolidated stable material on the Earth’s surface; plant growing material
- It’s loose and its on the surface rather than underneath, exclusively on the crust. Its active and a good medium.
- Extremely heterogeneous, highly variable
- Have to take care when using microscope techniques and not only test one small area and assume that representative of the sample as a whole.
- Made of distince layers called horizons.
14
Q
What determines soil type?
A
- The things that determine the soil type formed is: Climate, parent material, age, bio activity, topography determine soil type formation
- Is it hot? Is it arid? Is it cold? Wet? Dry? What rocks are present? Igneous? Sedimentary? What other things are in the vicinity that are making up the soil? Have there been earth worms making it fertile? Is it slopey? On a mountain?
- This is what makes it valaube as trace evidence as we can work out where it came from.
15
Q
What non-living things are found in soil?
A
Non-living: inorganic minerals, salt crystals, decaying plant/animal matter (humus), shells, insect exoskeletons, fossils, bones and teeth
16
Q
What living things are found in soil?
A
Living: bacteria, algae, fungi, plant roots, invertebrates, small mammals
17
Q
What unusual things are found in soil?
A
- Unusual: cement, plaster, metallic fragments, glass, paint flakes, paper, fibres, plastic fragments
- Good for trace evidence examination
18
Q
Study of soils
A
Pedology
19
Q
British Geological Survey – UK Soil Observatory
A
You can search almost any part of the UK by any criteria you can think of from analysing trace of soil and it will tell you where you would likely find that exact composition.
20
Q
Dirt
A
Dirt is a combination of dust and or soil, typically dry.
21
Q
Grime
A
Dirt mixed with liquid
22
Q
The older the soil…
A
The older the soil the more dense and fertile it is because its had longer to form.
23
Q
Dusts
A
- Particles generally <100 μm
- If <10 μm, can be transported thousands of miles
- Big repercussions when trying to determine background, persistence, activity level.
- Chemical composition varies considerably and is indicative of geographical area and the type of place it came from.
- Natural, industrial, household, street, water sources, etc.
- Natural dusts are basically mineral rock heavy.
- Industrial dust might have particles of soot.
- Household dust is usually skincells
- Street dust may have lots of different particles from like brake lorries and cars. It might have particles from exhaust fumes.
- Size of the dust particle may mean it did not originate where it was found.
- Can even be found in water
24
Q
Most abundant category of minerals?
A
- Silicates = SiO
- 6 different silicate classes
- Phyllosilicate class → sheets of repeating SiO4 tetrahedra, stacked in sheets.
25
Phyllosilicate class
- Type of silicate class
- sheets of repeating SiO4 tetrahedra, stacked in sheets.
* Gives a platey appear and allows them to fracture easily.
* Also known as “clay minerals”
* Muscovite (mica) is a phllosilicate material
26
Vermiculite
* Type of mineral is vermiculite – used as the insulating material in fire-resistant safes, chimneys, brake-linings, floor screed, concrete, fire-proof walls
* Come in different sizes which have different properties.
* Found anywhere you want fire retardant properties.
* Resistant to heat.
* Highly likely to be encountered as trace especially if someone has tried to break into a safe.
* They might end up with traces it on themselves under fingernails, shoes, etc.
27
Found in mascara
- Dentonite
- Hectorite
- Illite
28
Found in face masks
- Kaolinite (china clay) used in clay face masks
- Bentonite
- Hectorite
- Illite
29
Gemstones
Minerals that are cut and polished to be used in jewellery or as ornaments.
30
Forensic gemology
* Counterfeits and simulants
* Ways to tell the difference between gemstones and analyse them to decide if theyre genuine or fake:
* Luminescence, fluorescence, phosphorescence
* Fluorescence can be an intrinsic property
* Birefringence, refraction, dispersion, pleochroism
* Hardness, specific gravity, magnetism, piezoelectricity (pressure), pyroelectricity (heat), thermal conductivity.
31
Pizoelectricity
Pizoelectricty is electrical activity within the mineral when you apply pressure.
32
Pyroelectricity
Pyroelectricy is when you apply heat and thermal conductivity.
33
What is anthropogenic
Man-made
34
Concrete
* Block discovered in a garage in Cumbria in 2002
* Contained an entombed baby → “Lara”
* Evidence of abuse and may have been buried alive
* DNA of remains revealed parents (prime suspects)
* 15 years had passed, parents both deceased
* The baby was preserved so well, no maggots or bacteria was able to get to her.
35
Recovery of soil
- Take control samples from suspected contact points.
- Using a clean trowel sample the surface.
- Where a footwear is also recovered, leave any samples adhering to a cast in place but also take samples form the surrounding area.
- Package each sample separately in a operly sealed, heavy dutty paper bag.
- Alternatively consider placing samples in a tamper evident bag and freezing to reduce the likelihood of yeast or fungal growth.
- Include a sketch and photograph showing the areas sampled.
36
Analytical work flow for soil
* Gross examination, recovery and collection
* Preliminary evaluation of physical characteristics
* Physical fit assessment –Unlikely to get this
* All microscopic techniques – PLM is perhaps the most important type of microscopy when looking at geological evidence.
* Microspectrophotometry - colour determination is one of the most important elements for analysis
* Measurement of pH and electrical conductivity - Looking at whether the soil is acidic or alkali will give you an indication as to where the soil came from per the geological survey maps.
* Infrared spectroscopy – organic content
* Raman spectroscopy – inorganic and carbon content
* SEM-EDX – SE mode for surface topology & BSE mode for homogeneity
* XRD – crystal structure, polymorphs, good for minerals
* AAS, XRF, NAA, ICP-AES – elemental composition
* Isotopic analysis
* MVA
37
MVA for soil analysis
* Due to the amount of data you get from analysing soil residue and the number of techniques used to characterise that you end up with a huge amount of data which is suitable for MVA.
* Most widely used = HCA and PCA
38
Physical characters of soil
* Weight and volume
* Colour and texture
* For individual particles – dimensions, surface area, perimeter and shape (form, sphericity, angularity, irregularity)
* Angularity is how angled or sharp it is.
* Irregularity it how non shape like it is, are there protrusions, branched, etc
* Particle size gives it its definition
