Advanced Evidence Types

rocks sediments soils dusts minerals fossils anthropogenic e.g. concrete, bricks sediments soils and dust are mixtures of organic/inorganic particles where - organic fractions (hydrocarbon based, plant/animal based) derive from: biological processes, e.g. shells and forams (calcite, aragonite), phytoliths (silica), diatoms, or CHO based products (e.g. coal) - inorganic fractions include rock fragments, mineral grains and amorphous matter, e.g. volcanic glass

• weights to sink bodies • in bags containing illicit substances/firearms • as concealment material in smuggling cases • as projectiles (thrown or catapulted

• igneous - rocks formed from liquid magma cooled deep in the earth or extruded onto surface by volcanos • metamorphic - rocks formed by varying degrees of heat and pressure on any type of existing rock • sedimentary - rocks formed by accumulation of sediment in water and air by processes of erosion, precipitation, evaporation and compaction • sedimentary - around 70 % of earths surface

• predominantly made of 80-90 % diatoms (silica) aluminium oxide if forms of clay minerals, iron oxide • diatoms are useful form of TE • if diatomaceous earth in rocks, got something useful to look at • it is in food, medicines, cosmetics, absorbents, insulating materials, pet litter, even as a stabilising component in dynamite – chances of finding it are pretty high

• particle mixtures from a variety of sources, transported and deposited by air, water or ice • this makes sediments distinct from rock • gravel • sand • silt • clay

• encountered in casework in tyre treads, shoe soles, in drowning victim’s mouths/respiratory tract/clothing (in pockets/hoods/shoes), or on associated adhesive tapes (gagged or bound) • size discrimination: • gravel = 2 mm – 64 mm • cobbles = 64 mm – 256 mm • boulders = >256 mm • shingle = rounded gravel • found in driveways, flowerbeds, decorative reasons • also found in marine and lake environments because water is constantly eroding surface

• 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 (because it sediments) • when flush toilet or wash garments with sand – particles will be trapped • size discrimination: • sand grains = 0.063 mm – 2 mm • for a sediment to be classed as sand it must contain >50% sand grain sized particles otherwise gravel or something else • made up of many different minerals – rock fragments (lithic grains) – predominantly quartz

• encompasses silt and clay (smallest sediments) with some sand and gravel • mud particles typically = <0.063 mm • mud is any sediment that has a sticky character when wet so good form of TE • clings to stuff – big tick for transfer thinking about background transfer, persistence • chances of finding in UK is high • encountered frequently in casework on skin, under fingernails, on clothing/footwear, in/on vehicles; from coastal/river floodplains, fields, and woodlands • many samples also contain organic matter (grass, weeds, pollen)

• soil is unconsolidated stable material on the Earth’s surface (it is loose (isn’t a lump) and it is on the surface rather than inside the earth); plant growing material (it is biologically active – good medium) • extremely heterogeneous so good form of TE as is highly variable • but need to take care when using microscopic techniques to understand chemical variety in sample (cannot test one area and assume representative of whole sample) • soil is present on earth’s crust in distinct layers - horizons • soils are dictated by how they are formed or where they are found: • climate (arid, hot cold, wet, or dry) • parent material (what type of rock) • age (older soil = more fertile and denser, because longer it has had to form) • biological activity • topography determine soil type formation • soil is made up of: • non-living: inorganic minerals, salt crystals, decaying plant/animal matter (humus), shells, insect exoskeletons, fossils, bones, and teeth • living: bacteria, algae, fungi, plant roots, invertebrates, small mammals • unusual: cement, plaster, metallic fragments, glass, paint flakes, paper, fibres, plastic fragments

dirt - combination of dust and soil grime - wet dirt

• good form of TE as can work out where it is from using UK soil observatory database by British geological survey • database that lets you search almost any part of UK by any criteria you want • can put in anything found from analysing trace of soil and will tell where likely find that exact makeup/composition of soil • unusual components of soil (cement, plaster, metallic fragments, glass, paint flakes, paper, fibres, plastic fragments) are useful in TE too

• particles generally <100 μm • if <10 μm, can be transported thousands of miles • this size has big repercussion when trying to determine background, persistence, activity level • need to bear in mind that size of dust particle may mean it didn’t originate there – might have been carried in wind • chemical composition varies considerably and is indicative of geographical area or type of place it came from • natural, industrial (will be different might have soot from chimneys), household (predominantly skin cells), street (particles from brake dust/exhaust fumes), water sources, etc.

• another geological form of TE • silicate minerals • phyllosilicate class most interesting • comprised of sheets of repeating SiO4 tetrahedra - gives minerals from this class a crepe-y appearance and allows them to be fractured easily • also known as clay minerals • clay - geological sediment (< 2 um)

• vermiculite – grey mineral • bit like diatomaceous earth – it is everywhere • come in different sizes – have different properties • found anywhere you want insulating or fire retardant properties • used as the insulating material in fire-resistant safes, chimneys, brake-linings, floor screed, concrete, fire-proof walls • highly likely to be encountered as a form of trace especially if someone has tried to break into a safe and burgle it – may end up with traces of vermiculite on clothing, tools, shoes and under fingernails – might think it is just dues • muscovite (natural mica) • has repeating tetrahedral sheets – good mineral to use in makeup as soft and shiny • kaolinite (china clay) • in clay face masks • magnesium silicate (talc) • talcum powder • bentonite • face masks and mascara • hectorite • face masks and mascara • Illite (French green clay) • face masks • good for angry and red skin – soothing and calming properties

• another form of minerals • these are minerals that have been cut and polished to be used in jewellery or as ornaments • not likely that you are going to find gemstones as a trace material for example in tread of someone’s boots but might find in forensic gemology

• counterfeits and simulant gemstones • diamonds cost a lot, they can be simulated by a lot of other minerals but it takes an expert to differentiate them • ways in which forensic gemmologist can tell differences between various gemstones and analyse them to give their expert opinion to say if something is genuine of fake • luminescence, fluorescence (when irradiated with UV light, they emit visible light • phosphorescent - if the luminescence continues after the exposure to UV radiation. this happens due to impurities and defect in the crystal lattice • birefringence (most significant optical property used for the identification of gemstones) • refraction, dispersion, pleochroism • hardness, specific gravity, magnetism, piezoelectricity (electrical activity in mineral when apply pressure), pyroelectricity (electrical activity in mineral when apply heat), thermal conductivity (does it conduct heat as mineral)

• able to identify impurities and defects in the crystal lattice of gemstones

• measure the RI • if an isotropic substance is illuminated with normal incidence to the crystal face, all light passes through without deviation • diamond which have a cubic structure • opals (hydrated silica) which are amorphous • Snell’s law still applies as sin0 = 0 • velocity changes but not the direction of light

• tetragonal or hexagonal crystals • light incident on the cleavage face of the crystal will break into two separate rays as the light travels through the crystal • the waves of the two rays vibrate in planes perpendicular to each other and travel through the crystal at different velocities • the faster ray emerges from the crystal slightly ahead and in a different location to the slower ray • the two rays are known as the ordinary ray (O) and the extraordinary ray (E) • the two rays vibrate in different planes through the material and have different RIs • birefringence is the difference between these two refractive indices • as the polarisation of light changes through these materials, this can be measured

• means manmade • some are not fully manmade because they started life as natural minerals but we have done something to them to make manmade • concrete - mixture of aggregate and cement • cement is derived from natural minerals but we have processed them • aggregate is just gravel stones • bricks, roof tiles, pipes, pottery • all derived from natural clays but fired in a kiln - been changed • glazed ceramics • can date these as they are made in factory where records are kept and sometimes they have manufacturer stamp on bottom • plastic fragments • fibres • paint flakes • glass fragments • metal fragments

• take control sample from suspected contact points • using a clean trowel sample surface to which contact has been made (normally scraping the surface is sufficient as surface soil is to a depth no deeper than 16 cm) • if contact is suspected below 16 cm then contact lab • where footwear mark is also recovered, leave any samples adhering to cast in place but also take samples from surrounding areas • package each sample separately in properly sealed, heavy duty paper bag • consider placing samples in a tamper evident bag and freezing to reduce the likelihood of yeast of fungal growth • include a sketch/photograph showing areas sampled

• gross examination, recovery, and collection • preliminary evaluation of physical characteristics (physical fit assessment – most probative value but unlikely to get this – not going to get a piece of rock and say it fits exactly into other bit of rock. this is even less likely with soil as it is unconsolidated – it doesn’t have form) • all microscopic techniques – PLM • microspectrophotometry – colour determination • measurement of pH and electrical conductivity (soil pH – indicates where it is from as per geological survey maps, if soil is acid or alkaline) • 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 • AAS, XRF, NAA, ICP-AES – elemental composition • isotopic analysis (isotope ratio) • MVA – most widely used = HCA and PCA (hierarchical and principal component analysis) • get lots of data from analysing soil residue so MVA good for this

• weight and volume • colour and texture • Munsell soil/rock colour chart • for individual particles: • dimensions, surface area, perimeter, and shape (form, sphericity, angularity (how angled or sharp it is), irregularity (how non-shape like it is, is there any protrusions, is it branched)

• rust and metal shavings transferred to a persons clothing • metal filings on a pipe wrench after a twist attack on a doorknob • metal weapon used in an assault leaving trace in the wound • metal from a crowbar used to force open a window or door • gunshot residue • explosives residue • fireworks and sparklers • lightbulb filaments