Advanced Evidence Types Flashcards
What are the 7 kinds of forensic geology?
What can be said about 3/7 of these?
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
When are rocks encountered in forensic casework?
- weights to sink bodies
- in bags containing illicit substances/firearms
- as concealment material in smuggling cases
- as projectiles (thrown or catapulted
What are three main classifications of rocks?
Which one is most interested in as forensic perspective?
- 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
What is diatomaceous earth?
- 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
What are sediments and what makes them different to rocks?
What are four main categories of sediment?
- 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
Define gravel
- when encountered
- size discrimination
- rounded gravel
- 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
Define sand
- when encountered
- size discrimination
- for a sediment to be classed as sand…
- what is it made up of
- 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
Define mud
- smallest two constituents
- size discrimination
- definition
- encountered when
- what else do samples often contain
- 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)
define soil
- definition
- homogeneous/heterogeneous
- how is it found on earths crust
- how are they dictated
- what is it made up of
- 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
define dirt and grime
dirt - combination of dust and soil
grime - wet dirt
Why is soil a good form of TE?
- 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
Define dust (size, size repercussion, chemical compositions)
- 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.
define minerals
- definition
- most abundant category
- phyllosilicate class
- also known as
- define clay
- 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)
Where do we find different types of minerals
- vermiculite
- muscovite (natural mica)
- kaolinite (china clay)
- magnesium silicate (talc)
- bentonite
- hectorite
- Illite (French green clay)
- 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
What are gemstones?
Where are these likely to be found?
- 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
What does forensic gemology consist of?
How can forensic gemmologist tell difference between various gemstones?
- 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)
What does XRD allow for in forensic gemology?
- able to identify impurities and defects in the crystal lattice of gemstones
What is included in the optical analysis of isotropic substances?
What is an isotropic substance and give two examples
How does this work with Snell’s law?
- 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
What is a uniaxial substance and give two examples
What happens when light hits a uniaxial substance
What is included in the optical analysis of uniaxial substances?
- 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
What does anthropogenic mean?
Give examples of anthropogenic materials?
- 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
What are recovery considerations for soils? (suspected contact points, footwear marks, packaging, sketch/photograph)
- 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
What is analytical workflow for soil/geology analysis?
- 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
What physical characteristics should be observed in soil/geology analysis?
- 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)
How can metals be used as a form of TE?
- 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
What are primary techniques used in the analysis of metal trace evidence?
- SEM-EDX
- XRF
- XRD
- HPLC and GC-MS
- AAS
- LA-ICP-MS
- colour spot and presumptive tests also regularly used (particularly for GSR)
What is difference between two types of GSR?
inorganic:
- mainly from primer mixture, some from cartridge case
- historically heavy metal components, although toxic metal free primer more common now
organic:
- mainly from smokeless powder, composed of primary explosives, stabilisers, plasticisers, sensitisers, and flash inhibitors
- combustion products also found on spent cartridge and firearm muzzle
What are four categories of GSR detection?
1 - optical methods:
- organic compounds identified due to strong IR-luminescence
- methods non-destructive, rapid but low specificity and high LoD
2 - Chemographic testing:
- invasive but can be performed at crime scene
- most target inorganic elements with presumptive test
- high selectivity but only qualitative with risk of false positives
3 - spectrometry:
- primarily identify inorganic components
- SEM-EDX most common as it is quantitative, gives highest compositional and morphological detail, but takes time
4 - separation methods:
- particularly coupled with mass spectrometry e.g. LC/GC-MS/MS
- invasive method but reliable, specific and has a low LoD
How can metals be detected in latent fingerprints?
- of interest to be able to link activity with specific metal objects e.g. guns or explosives
- XRF microscopy could enable this
- needs large synchrotron to access this data with a high enough spacial and spectrographic resolution
- able to identify differences between handling gun barrel and ammunition cartridge background activity
How do we detect explosive trace evidence?
What is good about this technique?
What other techniques are available?
- currently use derivatives of ion mobility spectrometry (separates and identifies ionised molecules present in the gas phase based on their mobility in a carrier buffer gas)
- builds on the concepts of mass spectrometry - controlled ionisation and separation based on an ions interaction with an electric field to enable detection and identification
- measurements can occur in milliseconds, which makes it great for usage in situations where fast, reliable results are required e.g. airports
- techniques including GC/LC, SEM, FTIR, Raman & other spectrometric methods used to elsewhere to analyse the organic and inorganic components
Why are fireworks a great form of TE?
- fireworks are a great combination of multiple TE types: paper, plastic, explosives, metals
- all previous discussions of analytical approaches to these individual elements are of interest here
How are sparklers used?
What can explosive analysis techniques do for sparklers?
What about with chemometrics?
- sparklers are particularly interesting as commonly used to initiate inorganic homemade explosives
- explosives analysis techniques used to great effect to detect and identify a sparkler, they aren’t enough to distinguish between brands of sparkler
- combining ICP-MS to detect elemental profiles of 7 metal components (V, Co, Ni, Sr, Sn, Sb & W) with chemometric approaches to analyse the profiles has shown a discrimination with 100% match to sparkler manufacturer
How can a lightbulb filament be used as trace evidence?
- likely the lightbulb from a headlamp is going to be involved in analysis to answer:
- were the headlights illuminated?
- turning without indication?
- brake lights not working?
- as well as potentially linking at a hit-and-run or ram-raid
What are three types of modern automotive lightbulbs?
1 - halogen – most popular
- tungsten filament in glass tube with N/Ar
2 - LED – future challenge: range of semiconductors – small, metal doped
3 - xenon/high intensity discharge
How can lightbulb tungsten filament analysis tell us if lamp was illuminated at time of impact?
- tungsten is rigid and brittle at ambient temperatures and ductile at incandescent operating temperatures
- if filament was off - no pronounced distortion
- if filament was on - inertial force distortion on hot filament
- can use a multimeter to check if it still works
What is tattooing?
Why is the study of tattoos of interest to forensic science?
What can be subjective about tattoo analysis?
- the practise of puncturing the skin and introducing pigment which is retained by macrophages in the dermis of the skin
- the study of tattoos is of interest to forensic science for two main reasons:
1 - identification
2 - tracking movement of people and animals - the description of tattoos is open to interpretation
- chemical analysis removes interpretation issues
What are modern pigments made of?
Develop an analytical workflow?
- organic pigments (Azos) or mineral pigments (TiO2, iron oxide)
- all microscopic techniques – understand penetration depth and pigment distribution (just like with hair)
- infrared spectroscopy – organic binders and pigments
- raman spectroscopy – inorganic pigments
- SEM-EDX and XRF – elemental composition of layers
- pyrolysis-GC/MS and microchemical testing
