Chapter 5 Pollen and Spore Examination By the end of this chapter you will be able to: distinguish between and explain how pollen and spore evidence can be used in crime investigation define a pollen fingerprint classify the different organisms that produce pollen and spores compare and contrast the female and male reproductive parts in plants distinguish between gymnosperms and angiosperms All Rights Reserved South-Western / Cengage Learning © 2009 Forensic Science: Fundamentals & Investigations, Chapter 5

Chapter 5 Pollen and Spore Examination By the end of this chapter you will be able to: summarize the different methods of pollination and their relevance in solving crimes identify the different ways spores are dispersed state characteristics of pollen and spores that are important for forensic studies summarize how pollen and spore evidence is collected at a crime scene describe how pollen and spore samples are analyzed and evaluated Forensic Science: Fundamentals & Investigations, Chapter 5

Introduction Forensic palynology is a specialized field that studies pollen and spore evidence. 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

Pollen-Producing Plants Forensic palynologists know each pollen-producing plant provides a pollen fingerprint—a specific type of pollen grain. They also know there will be a certain number of grains 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

Gymnosperms Gymnosperms are the oldest seed plants. Evergreens are conifer gymnosperms. They produce their 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

Angiosperms The most recent plant group to evolve is known as the flowering plant. Identify its different parts in the illustration above. Plants in this group produce seeds in an enclosed fruit. These plants are very diverse and include corn, oaks, maples, and the grasses. 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

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

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

Spore Dispersal Algae disperse spores into water or air. Spore producers have the same value in investigations as pollen from wind-pollinated plants. Identify the different parts of the mushroom illustrated above and explain how its spores are released into the wind. Forensic Science: Fundamentals & Investigations, Chapter 5

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

Finding Pollen and Spores Forensic Science: Fundamentals & Investigations, Chapter 5

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

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

. . . . . . . . . . . . . . . . . Summary Forensic palynology can indicate something about the geographical origin and the time or season of a crime. Spores and pollen can be dispersed by wind, by water, or by animals. Pollen from insect-pollinated plants tends to give more specific location data than from wind-pollinated plants. Pollen collected at a crime scene must include baseline samples from the area for comparison. Collection of pollen and spore evidence must be performed carefully to avoid contamination. Forensic Science: Fundamentals & Investigations, Chapter 5