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Warm-Up Can you identify the mystery items? All the items are associated with crime scene investigations. #3 #1 #4 #2 The answers are … #3 #1 #4 #2 Pollen and Paint Evidence Palynology The study of pollen and spores Important to know: What is produced in a given area The dispersal pattern Variation in size and weight 4 Palynology • Since both pollen and spores have resistant structures, they at times can help determine such things as whether a body was moved, a crime’s location, whether it occurred in a city or in the country, or in which season it may have occurred. Forensic Science: Fundamentals & Investigations, Chapter 5 5 Pollen-Producing Plants • Pollen-producing plants provide a pollen fingerprint—a • specific type of pollen grain. A certain number of grains are found in a specific geographical area during particular times of the year. – Examples of non-seed plants would be ferns, mosses, liverworts, and horsetails. – Examples of seed plants would be gymnosperms (cycads, ginkgoes, and conifers like an evergreen) and angiosperms (flowering plants like roses). Forensic Science: Fundamentals & Investigations, Chapter 5 6 Gymnosperms • Gymnosperms are the oldest seed plants. • Evergreens are conifer gymnosperms. – seeds in a hard, scaly structure (cones). • Pollination occurs when pollen is transferred from the male cones to the female cones. • Which of the two structures shown above transfers pollen to the other? Forensic Science: Fundamentals & Investigations, Chapter 5 7 Angiosperms Petal Anther Stigma Style Filament Ovary with seeds Sepal • The most recent plant group to evolve is known as the flowering plant. • Identify its different parts in the illustration above. – Stamen (Male parts: Anther, Filament) – Pistil (Female Parts: Stigma, Style, Ovary) • Plants in this group produce seeds in an enclosed fruit. • These plants are very diverse and include corn, oaks, maples, and the grasses.8 Forensic Science: Fundamentals & Investigations, Chapter 5 Types of Pollination Pollination is the transfer of pollen from the male part of a plant to the female part of a seed plant. – Self-pollination, in flowering plants, involves transfer of pollen from an anther to the stigma within the same flower, as in pea plants. – Cross-pollination (illustrated above) involves two distinct plants. Forensic Science: Fundamentals & Investigations, Chapter 5 9 Types of Pollination • Pollen of self-pollinating plants is generally of lower value in forensic studies because it is rarely encountered. • Pollen can be carried by wind, animals, or water. • Pollen carried by wind may be less effective for determining direct links between individuals and places because of the long distances over which it can be carried. Forensic Science: Fundamentals & Investigations, Chapter 5 10 Spore Producers • Spore producers include certain protists (algae), plants, fungi, and the bacteria that produce a unique type of spore. • Bacterial spores, endospores, can cause diseases such as anthrax and botulism. • Spore analysis has the advantage that the spores possibly can be grown and the species identified with certainty. Forensic Science: Fundamentals & Investigations, Chapter 5 11 Spore Dispersal Cap • Algae disperse spores into water or air. • Spore producers have the same value in investigations as pollen from wind-pollinated Gills plants. • Identify the different parts of the mushroom illustrated above and Stem explain how its spores are released into the wind. Forensic Science: Fundamentals & Investigations, Chapter 5 12 Ring Volva Pollen and Spore Identification in Solving Crimes • • • Angiosperm pollen grains Gymnosperm pollen grains The outer shell of a pollen grain and spore (the exine) has a complex and unique structure. These are revealed under a microscope. Identification can provide important trace evidence in solving crimes. Forensic Science: Fundamentals & Investigations, Chapter 5 13 Finding Pollen and Spores Forensic Science: Fundamentals & Investigations, Chapter 5 14 How to Collect Pollen and Spores • During an investigation, control samples must be collected as well as evidence samples. • Samples must be collected wearing gloves and with clean tools (such as brushes and cellophane tape) and placed in sterile containers, which then must be sealed and labeled with care. • Sampling instruments must be cleaned after each use, or new ones must be used. • Collected evidence must be secured, and the chain of custody must be maintained. Forensic Science: Fundamentals & Investigations, Chapter 5 15 Analyzing Pollen and Spore Samples • To identify pollen and spores, specialists can use a compound light microscope, a scanning electronic microscope, reference collections that may consist of photos and illustrations or perhaps even actual dried specimens arranged systematically (herbariums). • Pollen and spore evidence that has been collected, analyzed, and interpreted can be presented in court. • These “fingerprints” can be used to confirm certain aspects of a crime. Forensic Science: Fundamentals & Investigations, Chapter 5 16 Paints and Coatings Introduction • Chemistry of paint very complex • Forensic role is to compare paint evidence from scene to known source • Individual evidence only in cases where large enough paint samples exist to physically match Definitions • PAINT: A suspension of pigment in a film former (also called vehicle) – Usually not a solution. Pigment is suspended in film former – Pigment is usually mixture of inorganic metal salts. Purpose is to impart color. – Film former is usually organic polymer(s). Purposes are to protect surface and hold pigments What are some of the uses for paint? • Art works • Decoration (residential paints) • Protection of a surface (rust inhibiting auto paints) • Warnings (reflective paint, fluorescent paint) Paint Cross Section Other Coatings • Varnish: A film former, commonly polyurethane, dissolved in a solvent, which normally doesn’t contain a stain. Purpose is to protect wood • Stain: A mixture of organic dyes dissolved in solvent. Made to penetrate wood and stain in. Does not protect • Enamel: originally a glossy, thermosetting paint. Now any paint which dries glossy Paint As Evidence • Paint chips: Pieces of paint which have come off surface. They usually contain all of the layers of the paint • Paint smears: The top layer of paint which has loosened owing to being wet or air oxidation. Smears onto another surface after brushing contact. Layer structure is not present Analysis of Paint • Color layer analysis – Requires cross section of paint chip – Cannot be done on paint smears – Same number and order of layers – Relative thickness must be same – Is a class test (but see case at end of lecture) Paint Cross Section Analysis of Paint • Solubility – Use solvents such as acetone, dichloromethane, pyridine. Acrylic lacquers are soluble in acetone • Pyrolysis GC – Analysis of film formers – Bulk technique, all layers analysed together Pyrolyzing Unit Analysis of Paint • Pyrolysis GC Analysis of Paint • FTIR – Fourier transform infrared spectroscopy – Collects spectral data (absorption, emission, etc.) – Will determine type of film former – Does not show pigments unless they are organic – Is a bulk method: if more than one layer is present, IR will be a composite FTIR of Automobile Paint Analysis of Paint • Electron microscopy – Inorganic pigments – Excellent for single, top layer analysis and paint smears • UV-visible spectrophotometry – Must be able to separate pigment from film former and dissolve it The Case of the 11 Layer Paint Chip • • • • Hit and run case Paint chips left at crime scene on victim Chips had 11 distinct layers of various colors Samples taken from suspect auto showed 11 layers with matching color-layer sequencing The Case of the 11 Layer Paint Chip • Paint examiner testified that paint found at scene CAME FROM THE SUSPECT CAR (individualized chip to car) • Defense attorney asked examiner the following hypothetical question: “What would your conclusion have been if there had been only 10 matching layers?” The Case of the 11 Layer Paint Chip • Where is the defense attorney going with this line of questioning? • Why does this question present a problem for the examiner? • How would you answer defense attorney’s question? The Case of the 11 Layer Paint Chip • One possible answer to question: “I cannot give you a definitive answer. I take each case on an individual basis and reach a conclusion based on the evidence in that case. It would not be possible to generalize about an optimal number of layers of paint that are present.”