Forensic botany PDF

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Forensic botany lecture...

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Forensic botany Suffolk Strangler case examples Definitions: Forensic Botany - use of plants and plant parts (pollen, seeds, leaves, flowers, fruits, and wood) Forensic Entomology: the use of insects, beetles, ants, bees etc… Forensic Geology/Geophysics: minerals, oil, petroleum, and other materials found in the Earth. Forensic Mycology: the use of Fungi. Forensic Palynology: the study of pollen and powdered minerals, their identification, and where and when they occur. Forensic Limnology : freshwater crime scenes, diatoms and algae. What is botanical evidence used for? -

Estimati on of body deposition time

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Estimati on of post mortem interval

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To determine actions of offenders

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As evidence of association

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To differentiate kill and deposition sites

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To establish cause of death

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Challeng ing witness testimony

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Eliminatio n of irrelevant locations

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Drug analysis

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Arson investigation

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Sexual assault -

Illegal Trade Cases

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Poisoning

Advantages of Botanical Evidence: - Plant matter is long lasting due to tough cell walls made of cellulose - Pollen grains and spores are also very resistant to degradation, covered in extra layer of waxes and proteins that give extra protection - Reconstruction - can be used along with other evidence to reconstruct a sequence of events

- If ground is disturbed by events such -

as a burial, new growth can help predict when the burial occurred –plant succession. Plant DNA “fingerprinting” can identify individual plants, genetically

Plant Succession: -

Plant succession is the order in which plants and grasses colonise an area Specific to the land type and require expertise in that particular ecology If an area of soil was recently disturbed, both the type of plant and the development stage can help identify how long ago the event happened There maybe more lush growth due to extra aeration of the soil

Collection and packaging of plant evidence: Collected in paper or cloth bags - nonporous material (i.e. plastic, glass, metal) encourages damp and bacterial growth Trace evidence (plant fragments) collected in small paper envelopes. All containment items must be checked prior to use for damage or tampering. Bags containing evidence must be sealed, signed, dated and have an evidence labelled completed and attached.

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Sometimes in the laboratory plant evidence may be dried and pressed (can last decades).

Plant growth patterns: Plants show characteristic growth patterns Normal Damaged Corrective growth - time since disturbance Seasonal - Variation - Deciduous trees Seeds, pollen, spores Stinging nettles - Urtica diocia - behaviour change after damage, regrowth after damage follows pattern

Forensic Palynology: Study of pollen grains fern and fungal spores Advantages Invisible to naked eye – missed by perpetrators. Extremely resistant to degradation. Each species of plant has a unique type of pollen grain. Can identify specific habitats through pollen . Pollen seasonal patterns are predictable and well studied. Palynology: Pollen and spores Parts of the reproductive cycle in plants Pollen carry the male gametes of the higher plants e.g flowers, cones Spores are asexual reproductive bodies of lower plants e.g mosses, ferns, lichen Pollen is the sperm of the plant world

Pollen rain Wind diapers pollen is most often used in forensic palynology Most fall to the ground within one mile of the parent plant - pollen rain Analysis of pollen ties found at one site scan indicate the variety of plant life in the larger area Pollen rain will change throughout the year according to the seasons of the plants in the area (can indicate time of incident) Pollen collects in hair, clothing and in orifices/openings within the body, on shoes and get transferred into vehicles Pollen can be breathed in and get trapped in the skull - may also indicate time of incident.

Pollen dispersal:

Pollen grain:

Very small - 0.025mm in diameter A grain of rice is 6mm long Thats 1200x bigger than a pollen grain Each genus /species has a unique combination of size, shape and colour pollen which allows the identification of the species via microscopic analysis. Exine outer wall : Strengthened by chemical, waxes and proteins secreted by the pollen cell. DECAY RESISTANT.

Staining pollen: - Pollen is very variable and this helps with identification - Shape, aperture, ornamentation - Pollen grains are naturally shades of green , brown and yellow and are quite pale. So they are stained to enhance contrast before microscopic examination

- Safranin – Red stain. - Acid Fuchsin - Pink.

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- Pollen slides: - Pollen grains are mounted in glycerol or DPX, both have advantages and disadvantages. Glycerol roll the pollen grain and visualise in different orientations. However, eventually the grain will swell and burst. DPX is a permanent and pollen will be stuck in whatever orientation it was in when the DPX dried. Causes dehydration and wrinkling of the pollen which can obscure surface features. Crime scene samples won’t be as clean and easy to visualise as pollen taken directly from the plant - chemical processing to clean up and concentrate.

Identification of pollen: Light microscope or for 3D images a Scanning Electron Microscope. Compare the ‘questioned’ pollen sample to reference pollen samples. Why do pollen and spores make good evidence? -

Morphologically diverse – can readily distinguish between many species

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Geographically dependent

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Persistant

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Readily transferred

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Resistant

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Smaller scale than geological indicators (like soil/rock types) -

Possible because every site is different

How do we know that person has left the scene? Route 1 - the path: -

Wind pollinated trees/plants/fungi such as species of Hazel (see picture below) can spread their pollen or spores over large areas given the right conditions. Many of these pollen grains will end up on the woodland floor, including on the path itself. This pollen can be picked up in the form of soil assemblages on footwear.

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In addition to this, pollen could fall directly onto an individual on close proximity or with direct contact of the flowering body. This will only be the case if the tree is flowering AT THAT TIME.

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It is NOT common for physically pollinated plants to shed pollen even short distances unless disturbed, this is especially true where the pollen is enclosed in the flower (see Bluebell). Someone walking down the path would most likely not encounter fresh pollen of this kind.

Route 2 - the undergrowth: -

Wind-dispersed pollen and spores should still be present as with the footpath.

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Direct contact with flowering plants (and fungal fruiting bodies) can lead to “clumps” of pollen or spores in high concentration, sometimes even in visible amounts.

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Some plants will remain forensically “rare” despite physical contact (e.g. Bluebell, Snowdrop) due to flower shape.

Path is lined with grasses which are wind pollinated. However, these are not currently in flower. Colourful flowering plants either side of the path are most likely insect pollinated and as such are unlikely to spread to path in any number. Pollen is rarely found for long on concrete, metal or paving.

Persistance and resistance: Clothing (Bull et al 2006) -

Material type is the most important factor Mechanism of transfer is important Exponential decay

Vehicle fires (Morgan et al 2013) - 3 different pollen types identifiable after 30 minutes of exposure to 400 degree - Pollen threshold temperature of at least 500 degrees for short 3 minutes exposure - Footwells and wheel arches unlikely to be destroyed in vehicle fire Footwear (Morgan et al 2006)

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Forensic analysis of sediments recovered from footwear. The preservation of sediment on a shoe sole will vary, with certain areas generally retaining more sediment than others.

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5% remaining after 36 hours.

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4-5% after 4 weeks of normal wear.

Soil sampling: All pertinent locations Offender Victim Clean, new tools and PPE for each site and sample. Vegetation and soils- what has been in contact? Surface 2-3mm Footwear marks Grave sampling GPS for sample location. Preservation Paper Drying Refrigeration Vehicle sampling: Foot Pedals Footwells - remove carpets, separate pan and brush Internal muddy marks Chassis, tyre sidewall, bumpers, number plates & wiper drainage area...