Soil and Botanical Evidence: Composition and Comparison

Compare mineral, organic, biological and manufactured components as relevant. A common grain or brick fragment alone is not a locality signature.

A soil deposit can contain mineral grains, organic matter, water, biological material and manufactured particles. Relative proportions, grain characteristics and associations can help compare deposits. The collection unit may be a small mixed smear rather than an intact geological profile.

Horizons and disturbed deposits vary. Document the actual profile rather than assume every site has four intact layers or every shoe sample comes from a particular horizon.

A horizon is a region with recognisable soil properties within a profile. Surface vegetation, excavation, imported fill and movement can disrupt or mix horizons. Document the sampled depth and disturbance, and do not assume a shoe or tyre preserves the original sequence of layers.

Select questioned and comparison locations to assess plausible contact and spatial or depth variation. Keep them identified separately.

Collection spacing, depth and preservation depend on the question. Drying may alter biological or chemical targets; obtain specialist instructions rather than dry every sample automatically.

Useful references include relevant contact areas and reasonable alternative locations, not only the investigator’s favoured site. Photograph the setting and label the precise source. Plan preservation with the receiving specialist if pollen, plant fragments, DNA or other biological components are also relevant.

Colour, particle size, microscopy, mineral analysis and other suitable methods provide different comparisons. Match moisture and preparation conditions when comparing colour.

Do not assign fixed discrimination rankings or turnaround times. A difference needs assessment against sampling variation and method uncertainty.

Colour can be recorded using hue, value and chroma under stated conditions. Microscopy characterises particles, while appropriate mineral or elemental examinations address other components. Consistent preparation matters because moisture, sieving or selective particle loss can change a comparison.

Pollen assemblages and plant material can inform environmental comparisons, but one species does not pin a vehicle to a precise region or date.

Microbiome localisation needs appropriate validation and reference coverage. Diatom findings require specialist interpretation and do not independently prove drowning or a unique water source.

Explain the relevant alternative sources, within-site variation and possible dependence between findings. Do not turn several class correspondences into unique locality attribution.