91 Botany in forensic science

Transcription

1 91 Botany in forensic science by Susan Fiddian BSc (Hons), MSc Scott Azzopardi BSc (Hons) [Updating authors] Des Carroll BSc (Hons), MSc [Original author] Update: 64

2 EXPERT EVIDENCE Author information Susan Fiddian has worked as a forensic scientist in Victoria since She holds the Degrees of Bachelor of Science (Honours) and Master of Science in Botany from the University of Melbourne. She is currently the Manager of the Botany Branch of the Victoria Police Forensic Services Department. She has given expert evidence in courts throughout Victoria and has run national training courses and workshops for forensic scientists. She is a sessional lecturer for two tertiary forensic science courses and has presented papers at several forensic science symposia. She is a past President of the Victorian Branch of the Australian and New Zealand Forensic Science Society. Susan Fiddian can be contacted at: Botany Branch, Victoria Police Forensic Services Centre 31 Forensic Drive Macleod VIC [email protected] Scott Azzopardi has worked as a forensic scientist since He holds the Degree of Bachelor of Science (Honours) from Monash University. He is currently a caseworker in the Botany Branch of the Victoria Police Forensic Services Department and has given expert evidence in Victorian Courts. Scott has also worked in the area of quality management and is involved in lecturing on the subject of Forensic Botany to police and tertiary students. He has presented papers at a number of forensic science symposia. Scott Azzopardi can be contacted at: Botany Branch, Victoria Police Forensic Services Centre 31 Forensic Drive Macleod VIC [email protected] Susan Fiddian and Scott Azzopardi would like to acknowledge the enormous amount of work that Des Carroll put into the original edition of this Chapter. The original work has been updated with the addition of new references, case studies and areas of forensic botany that have emerged since the Chapter was first written but various case studies from the original Chapter have been retained. The author thanks Dr Lynne Milne for reading the section on pollen and spores, providing advice in this area and providing the pollen photomicrograph and scanning electron micrograph and Dr Steven Brett for providing the diatom photomicrographs. Special thanks also go to colleagues Kylie Slattery and Debra Ryan for their assistance. Chapter 91 S Fiddian, S Azzopardi and D Carroll Published with permission of the authors Expert Evidence

3 TABLE OF CONTENTS INTRODUCTION... [91.10] EXAMINATION OF ILLICIT PLANTS... [91.50] Cannabis... [91.60] Opium Poppy... [91.70] Catha edulis... [91.80] Other illicit plants... [91.90] BOTANICAL TRACE EVIDENCE... [91.120] Background... [91.120] Fragmentary plant material... [91.130] Seeds and fruits... [91.140] General aspects... [91.140] Forensic applications... [91.150] Starch... [91.160] Microscopic plant material... [91.170] Diatoms and other microalgae... [91.170] Pollen and spores... [91.180] Wood... [91.190] General aspects... [91.190] Identification of wood... [91.200] Forensic applications... [91.210] Identifications... [91.210] Physical fits and matching of growth rings... [91.220] EXAMINATION OF PAPER (DATING AND COMPARISON)... [91.260] NON-BOTANICAL ANALYSIS OF PLANT MATERIAL... [91.300] Identification using chemical tests... [91.300] Chromatography... [91.310] Enzyme linked immunosorbent assay (ELISA)... [91.330] DNA analysis... [91.340] PATHOLOGY AND TOXICOLOGY ASPECTS... [91.380] Drowning diagnosis... [91.390] Gastric contents... [91.400] Investigational aspects... [91.410] Plant toxicology... [91.420] DATING OF EVENTS... [91.460] Growth rings of woody roots and stems... [91.470] Estimation of the age of plants and plant parts... [91.480] Dating trauma to plant parts... [91.490] Plant colonisation of objects... [91.500] DETECTION AND EXAMINATION OF GRAVE SITES... [91.540] Grave detection... [91.550] Grave examination... [91.560] [The next text page is 91-51] 91-3 Update: 64

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5 Abbreviations AFLP...amplified fragment length polymorphism ELISA...enzyme linked immunosorbent assay GC-MS...gas chromatography-mass spectrometry HPLC...high performance liquid chromatography IEF...isoelectric focusing PCR...polymerase chain reaction RAPD...random amplified polymorphic DNA RFLP...restriction fragment length polymorphism SNP...single nucleotide polymorphism STR...short tandem repeat THC...tetrahydrocannabinol TLC...thin-layer chromatography ABBREVIATIONS Update: 64

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7 Glossary achene a dry, indehiscent one-seeded fruit with a leathery or membranous pericarp. anatomy the study of the structure of a plant and any of its parts. anemophilous pollinating, or dispersing spores, via the wind. angiosperms flowering plants which have their seeds protected within the ovary. cambium a cylindrical layer of actively dividing cells lying just below the bark in woody species. These cells allow the stem or root to grow in girth. cultivar a plant variety that has been produced in cultivation. dioecious a plant with separate female and male individuals. ecology study of the relationship between organisms and their environment. endosperm the nutritive tissue present in seed plants and derived from the embryo sac. It nurtures the embryonic plant during germination. fruit a mature gynaecium (the ovule-bearing structure of a flower), together with accessary structures when present. genus (plural genera) a unit of classification of organism consisting of two or more related species, or a single species with no known close relationship to another species. gymnosperms seed-bearing vascular plants with naked seeds, unprotected by an ovary wall. hardwood the wood of angiosperms. hermaphrodite a sexually reproductive structure (eg flower) with both male and female functional parts. hilum a scar on a seed from an earlier attachment to a funicle. monoecious separate male and female flowers on the same plant. monospecific a genus containing only one species. morphology the study of the form of a plant (external features) and its development. pappus a tuft of bristles, hairs or feathery processes on fruit of the family Asteraceae. pericarp the matured wall of an ovary which encloses the seed and forms the outer structure of a fruit. seed the structure formed from an ovule after it has been fertilised. It is comprised of an embryonic plant and food reserves. softwood the wood of conifers (cone bearing plants). species the lowest unit of classification, used where individual plants within a group show the greatest mutual resemblance. These individual plants are able to breed among themselves but not with plants of other groups (species). starch the main food storage component of plants. It is an insoluble carbohydrate which is easily broken down. taxon (plural taxa) unit of classification of organisms (eg species or genus). GLOSSARY Update: 64

8 EXPERT EVIDENCE taxonomy the systematic classification of plants and other organisms. variety a taxonomic unit below species. [The next text page is ] Expert Evidence

9 INTRODUCTION [91.10] Forensic botany is a very broad discipline which utilises many specialist skills. The majority of the work involves examination of botanical material (often trace amounts) to identify illicit plants or to ascertain possible links between a suspect, victim and a crime scene. However, this area of forensic science has a diversity of additional applications including: locating crime scenes; determining the time of an event (ie, time of year or number of years since an event occurred); reconstructing events; drowning diagnosis; investigating war crimes; providing intelligence for drug investigations; and establishing evidence of illegal importations (eg contaminants such as pollen, seeds or plant fragments can indicate a country or area of origin). It is the aim of this Chapter to provide an overview of the range of its applications. While botany may be simply defined as the study of plants, it encompasses many specialist fields, including taxonomy, morphology, anatomy, ecology and DNA analysis. All of these areas play a role in the forensic application of this science. Plant taxonomy is the systematic classification of plants that reflects their evolutionary progression. It operates via a strict set of principles and rules established by the International Code of Botanical Nomenclature and is used to classify in excess of 300,000 different species of plants present on this planet. Species are assemblages of similar individuals which have been classified into distinct groups. The basis for this grouping is the similarity of their morphological and anatomical features plus their ability to successfully interbreed among themselves but generally not with other such groups. Some species are divided into subspecies (where characters vary across a wide geographical range) and/or varieties (differing in a minor way from the typical form) or horticulturally into cultivars. The latter are varieties that have been bred, and are subject to a separate set of nomenclature principles the International Code of Nomenclature for Cultivated Plants. Taxonomically similar species are grouped into genera (singular genus). Genera displaying similarities are grouped into families, similar families into orders, orders into classes and finally classes into divisions. A species name or scientific name (eg Eucalyptus leucoxylon) is composed of the generic name (Eucalyptus) and its specific epithet (leucoxylon). There is only one correct or valid name per species and all scientific names other than the valid name are termed synonyms. Scientific names and classification of taxa often change as a result of taxonomic research. The use of common names can cause confusion as such names can refer to various, often unrelated, plants. For example, the common name Wild Mint applies to three different species: Mentha Update: 64

10 [91.10] EXPERT EVIDENCE diemenica, Salvia reflexa and Stachys arvensis. In addition, some species have more than one common name, eg Echium plantagineum is widely known as both Salvation Jane and Paterson s Curse. Therefore, botanists prefer to use scientific names. (See Lumley and Spencer (1991) for a comprehensive explanation of plant classification and nomenclature.) Common names are especially prevalent with wood because the timber industry and many lay people ascribe names to the timber s workability and general appearance without reference to the species itself or its botanical standing. The Standards Association of Australia has published a useful set of nomenclature listings detailing botanical names and their standard trade (or common) names: Standards Association of Australia (1983). Each particular species of plant is described in concise botanical terminology in the scientific literature. This terminology describes the external features (or morphology) used to classify that species, ie the appearance and structure of its stem, leaf and floral parts. A study of the internal features of plants (anatomy) may be of taxonomic value in delineating a species but it also serves to identify particular isolated plant parts. The cellular arrangement of individual plant cells and their types vary from one part to another in a characteristic manner. For example, root and stem parts are easily distinguished by their different arrangements of water- and food-conducting tissues. Furthermore, such cellular arrangements may be characteristic for particular taxa. Ecology is the study of relationships between the individual plant, its species population, and the myriad of biotic and physical components of its habitat. The biotic component covers all other forms of life including different plant species, other individuals of the same species and other living organisms such as worms, herbivores and humans. The physical components cover the non-living factors, such as climate (temperature, rainfall, day length, wind, frost etc), topography (land surface shape) and edaphic (soil type) factors. The success of a particular species can be gauged by its ability to propagate itself under a certain set of conditions. Some plants are tolerant to a broad range of varying ecological factors and are widespread, eg Cleavers (Galium aparine). Other plants are ecologically more fragile and have a restricted distribution, eg mangroves (various species including Avicennia marina) which grow exclusively in scattered muddy areas close to the sea. Plants with a restricted or limited distribution are extremely useful in forensic science as they are indicator plants, highlighting a defined locale. Generally, a botanist will aim to identify an unknown plant specimen to species level in order to obtain as much information as possible about the plant. Unfortunately, in forensic work the specimens are often fragmentary and one is forced to work with what is provided as evidentiary material. Frequently a species identification is not possible with incomplete material. Depending on the circumstances of the case, the forensic scientist may have to use many or all of the fields of botanical speciality discussed earlier so as to provide the best possible information to the courts. General references on various aspects of forensic botany, including a variety of case studies, can be found in Miller-Coyle (2005); Robertson (2004); Demmelmeyer and Adam (1995); and Bock and Norris (1997). [The next text page is ] Expert Evidence