Forensic botany is the study of plants and plant remains in the aid of a criminal investigation. This would include the analysis of wood, fruit, seed, twigs, leaves, plant hairs, pollen, spores, and algal cells. Though plants and their constituents are found almost everywhere, their great morphological diversity makes them distinctive, allowing for comparisons and ‘matches’ to be made between samples. Forensic palynology, a branch of botany, is the study of pollen and spores in criminal investigations. Pollen and spores are generally seasonal and often geographically specific, making them beneficial in linking a suspect, victim or object to a particular scene. These minute and light substances can easily be breathed in or stick to hair and clothes. However the lightness of pollen also means it can easily cause cross-contamination. The seasonal production of certain pollens can help investigators develop a timeline for a particular event. For example, if a buried body is discovered bearing pollen only found in summer, this would suggest the season in which the victim was buried. Unfortunately the pollen of grasses are fairly featureless, meaning that despite their commonality, they are not useful in forensic investigations. However seeds and fruits often have very specialised features, giving them particular forensic botanical importance. The production and dispersal patterns of spores and pollens are known as pollen rain. While they are scattered in a variety of ways, Anemophilous (wind-pollinated) are the most common type of pollen.
The study of such evidence can help determine the location of a crime, the time of year in which it occurred, whether a body was buried and for how long, and the location in which a suspect was present. Palynology can also be utilised in drug detection, as substances such as cannabis and cocaine are derived from plants. Techniques may be able to link drug samples to a specific batch or location. It may also be possible to obtain trace evidence from plant cells found in gastric contents, seeing as seeds and plant components are common food sources. These materials may help investigators pinpoint the rough time of the victim’s last meal, helping develop a timeline of events. Certain techniques can be employed to determine how long a body has been in a particular spot. Dendrochronology, the process of the counting of the rings in a root, can be used to determine when a body was buried, usually within a year. An array of information exists on the growth rates of different plant species, allowing the investigator to utilise this data to make estimations relevant to the case.
Forensic geology utilises geological methods to aid criminal investigations, namely with the study of soils, rocks and minerals.
Soil is a natural body composed of the decayed organic matter, rocks, minerals, and fossils, the study of which is pedology, a sub-specialty of geology. Its properties are affected by the five forming factors – parent material, topography, climate, organisms, and time. Parent material refers to the material from which the soil is originally formed. The topography relates to the physical configuration and features of a land formation. The climate, including heat, rain, ice, and wind, affect the speed of the soil formation process. Plants and animals will also affect soil formation by influencing the amount of water and nutrients available. All of these factors occur over a period of time, which may be hundreds or even thousands of years. A soil profile refers to the appearance of the soil when cut from the ground, composed of numerous layers known as soil horizons. These horizons may be from a few millimetres to over a metre thick.
Soil samples are frequently collected from crime scenes for later comparison to suspect samples. Perpetrators may often carry soil away from the scene on their shoe, clothes and cars. Layers of soil will be disturbed when graves are dug, the soil often being carried away from the scene on shovels and the offender’s clothing. Soils of a darker colour suggest the increased presence of organic matter, a common sight at gravesites. During the comparison of soil, the geologist will look for unusual or rare particles or particle combinations that may help distinguish between samples. This comparison is often conducted using petrographic microscopy, in which thin sections are mounted on slides to be viewed as light filters through its particular attachments. Scanning electron microscopes are also utilised in these analyses.
The minerals present in a sample of soil can further distinguish it. Whilst there are over 4000 varieties of mineral, only 20 of these are considered common, and most soil samples will contain only 4 or 5. The individual combinations of minerals, along with other identifying factors, are utilised by the geologist to distinguish between soils from different areas.
Rocks are naturally occurring collections of minerals formed by one of three processes. Igneous rocks are produced by the melting of older rocks, metamorphic are formed by pressure, and sedimentary rocks are formed by continuous weathering. Another common task of the forensic geologist is the interpretation of photographs and videos. This can shed light on the location in which the images were taken.