Forensic Botany: Current State of Knowledge and Possible Applications in Investigative Practice

FORENSIC PRACTICE dr Daria Bajerlein (corresponding author) Assistant professor at the Department of Animal Taxonomy and Ecology, Faculty of Biology, Adam Mickiewicz University in Poznań [email protected] prof. dr hab. Maria Wojterska Head of the Department of Plant Ecology and Environmental Protection, Faculty of Biology, Adam Mickiewicz University in Poznań dr Łukasz Grewling Assistant professor at the Laboratory of Aeropalynology, Faculty of Biology, Adam Mickiewicz University in Poznań dr hab. Mikołaj Kokociński Assistant professor at the Department of Hydrobiology, Faculty of Biology, Adam Mickiewicz University in Poznań Forensic botany: current state of knowledge and possible applications in investigative practice Summary Forensic botany is a science that studies biological traces of plant origin with regard to their practical usefulness as evidence used in judicial proceedings. Among the disciplines of forensic botany, the following have the widest application: palynology, plant anatomy, diatomology, plant ecology and plant molecular biology. It has been shown that the knowledge of plants can be used to determine the connections between the alleged perpetrator, victim and crime scene. In practice, the methods of forensic botany have been used to identify locations where the hostages were held or the sites of concealment of a corpse, distinguish between the place of the incident and that where the victim was abandoned, identify the perpetrator, the cause and time of death, unravel drug distribution networks, clarify the circumstances of plant and animal smuggling as well as war crimes. Despite the fact that the suitability of forensic botany for determining the circumstances of criminal events has been repeatedly confirmed, this science remains largely underestimated and scarcely used. This article presents the current state of knowledge in the field of forensic botany, characterizes its specific disciplines, possibilities and limitations relating to the application of the methods of forensic botany in investigative practice as well as outlines the perspectives of its further development. Keywords forensic botany, palynology, diatomology, plant anatomy, plant ecology, plant molecular biology, biological traces Introduction literature, the methods offered by forensic botany remain undervalued and only rarely used, despite As regards investigations, biological traces of human the fact that their suitability for forensic investigations origin, including various body secretions, excretions has been confirmed on numerous occasions [1–6]. and tissues are among the most frequently collected The main reason for insufficient usage of forensic potential evidence at the scene. Notwithstanding the botany methods for law enforcement purposes, foregoing, biological evidence also includes the traces lies in the lack of awareness of the existence of of animal and plant origin. Recent years have shown biological traces as well as lack of knowledge about the usefulness of insects in determining the time, place the methods of identification and preservation of such and cause of death. While the necessity of collecting traces. Nowadays, only in a few countries, such as biological material of human origin is undisputed and New Zealand, Great Britain or the United States, it is awareness of the existence of entomological evidence common practice to consult botanists. The aim of this has been growing among the investigators, biological article is to present the current state of knowledge on traces coming from plants are frequently ignored. forensic botany, possible applications in investigative As has been repeatedly emphasized in specialist proceedings and perspectives of further development. ISSUES OF FORENSIC SCIENCE 289(3) 2015 71 FORENSIC PRACTICE Forensic botany is a science dealing with evaluating of literature on the subject of forensic botany is plants for their potential use for law enforcement available in English language. There are relatively few purposes. It comprises several disciplines, such as: works in Polish [18–21]. While the first documented palynology (the study of pollen grains), diatomology application of forensic botany methods in forensics (qualitative and quantitative studies on diatoms), in contemporary times appeared already in the first plant anatomy (the study of the internal structure of half of the 20th century, the intensive development of plants), plant ecology (the study of plant-environment this science started at the turn of the millennium [2]. interactions, plant distribution and abundance) and Generally, particular disciplines of forensic botany plant molecular biology (the study of plant DNA). deal with research on the methods of revealing and Studies have so far shown that single-celled algae recovering botanical traces as well as linking them with and plants belonging to the majority of systematic the circumstances of the event. Notwithstanding the groups, beginning with the simplest forms and ending above, much attention is paid to presenting limitations with angiosperms, can be successfully used to clarify in the use of botanical traces for investigation the circumstances of the offense [7–9]. There is an purposes. extensive range of potential applications of forensic botany in forensics, mostly due to the fact that it helps to find answers to some key questions in the Forensic palynology investigation, concerning the time, place and cause of death as well as the perpetrator. In practice, the The earliest and at the same time most intensively methods of forensic botany can be used to identify developed discipline of forensic botany is forensic locations where the hostages are being held or the palynology. The first references to its usability sites of concealment of a corpse, distinguish between in explaining the circumstances of the offenses the place where the murder was committed and that appeared in the 1930s [22], but it was introduced into where the victim’s body was abandoned, identify the forensic practice not until 20 years later [23]. Forensic perpetrator, the cause and time of death, unravel drug palynology undertakes research on pollen grains and distribution networks, clarify the circumstances of plant spores for law enforcement purposes. Pollen grains and animal smuggling as well as war crimes [10–13]. are microscopic structures (invisible to the naked In general, the use of botanical knowledge in eye), ranging in size from 5 to 200 µm, containing investigative proceedings is based on two assumptions. male germ cells and thereby playing a key role in the The first assumption is Locard’s exchange principle, process of fertilization. The spores, produced by fungi according to which, any contact between two objects and cryptogams, including mosses and ferns, are will result in a mutual exchange of matter. This means, responsible for sexual reproduction thereof. Pollen and that botanical trace evidence can be used to infer links spores are collectively referred to as palynomorphs. between the scene, the victim and the perpetrator. For Forensic analysis is mostly based on the examination example, pollen grains revealed on the suspect’s shoes of pollen, whose certain features predispose it to serve or clothing may help to establish his/her identity as the as evidence. perpetrator [14]. The second assumption conditioning the use of forensic botany methods relates to the distribution of plant species around the world, i.e., the Traits of pollen grains useful for forensic analysis issues covered by phytogeography. Particular plant species are characterized by different environmental Due to the limited size, pollen grains are easily requirements, especially as regards soil conditions, transferable between objects. It has been shown that temperature, humidity and sunlight. Many species are pollen can adhere to practically all kinds of surfaces, tolerant of a broad range of environmental conditions, including organic (leather, cotton) and artificial (latex) hence their wide occurrence. Conversely, less tolerant material [24]. In forensic practice, pollen has been species are present at specific locations, easy to define revealed on clothing [10], shoes and soil in shoeprints and find. Knowledge of geographic and environmental [25] and hair [11]. Especially, the hair of the head and specificities can be used to determine relationships eyebrows make an excellent trap for pollen grains. The between the scene, the victim and the perpetrator. For persistence of pollen in the hair depends on how often instance, the presence of plant species on the victim’s it is washed and also on the use of various cosmetic body that are uncommon in the environment where the products, such as hairspray, gels or waxes (increasing corpse was found, may suggest that the corpse has adherence of pollen) [11, 26]. Pollen has been also been moved after death. revealed on the body surface [26] as well as inside There is an extensive literature on forensic botany, the corpse, during the autopsy [26–27]. Pollen grains including original and methodology papers, review inhaled through the nasal passage are retained by articles and case reports. The most numerous are mucus secreted within the nasal cavity. After death, methodology-case papers and review articles. Also pollen can remain preserved around nasal turbinates, available are several manuals [15–17]. The majority even in skeletonized corpse. There are several 72 ISSUES OF FORENSIC SCIENCE 289(3) 2015 FORENSIC PRACTICE articles on the methods of retrieving

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