Forensic Science: Fundamentals & Investigations, Chapter 5 1 distinguish between and explain how pollen and spore evidence can be used in crime investigation

Forensic Science: Fundamentals & Investigations, Chapter 5 1

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

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Chapter 5 Pollen and Spore Examination By the end of this chapter you will be able to:


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


IntroductionIntroduction

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.


Pollen-Producing Plants 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 # of grains found in a specific geographical area during particular times of the year.

– Non-seed plants ferns, mosses, liverworts, and horsetails

– Seed plants Gymnosperms - cycads, ginkgoes, and conifers like an

evergreen Angiosperms - flowering plants like roses


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??


Angiosperms

The most recent plant group to evolve is known as the flowering plant.

Know the identify of its different parts Plants in this group produce seeds in an enclosed

fruit. These plants are very diverse and include corn,

oaks, maples, and the grasses.

Angiosperm growth background


Angiosperm components



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.


Types of PollinationPollen of self-pollinating plants is generally of

lower value in forensic studies because it is rarely encountered.

Pollen can be carried by:– Wind– Animals– 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.


Spore ProducersSpore 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.


Spore Dispersal

Algae disperse spores into water or air. Spore producers have the same value in

investigations as pollen from wind-pollinated plants.

?? Can you identify the different parts of the mushroom illustrated above and explain how its spores are released into the wind??

Gymnosperm components



Pollen and Spore Identification in Pollen and Spore Identification in Solving Crimes Solving Crimes

Angiosperm Gymnosperm 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.

Pollen grains

Pollen grains


Finding Pollen and Spores

FYI


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)

Samples must then be placed in sterile containers, which then must be sealed and labeled with care. – Paper bags used for ‘wet’ collection items to allow to dry and to

prevent degradation

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.


Analyzing Pollen and Spore Samples

To identify pollen and spores, specialists can use a variety of electronic machines:– 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.

Spores & Pollen @ Crime Scenes

A short list of cases show many ways pollen is now being used in the courtroom: ForgeryProduction and distribution of illegal drugsAssaultsRobberyRapesHomicideGenocideTerrorismArsonHit and run crimesCounterfeiting of currencyIdentifying the origin of fake prescription drugs such as Viagra

Forensic Science: Fundamentals & Investigations, Chapter 5 18 http://askabiologist.asu.edu/pollen-and-solving-crime

An advantage that Spores have over Pollen is that they can be grown


. . . . . . . . . . . . . . . . . Summary. . . . . . . . . . . . . . . . . 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.

Documents

Forensic Science: Fundamentals & Investigations, Chapter 5 1 distinguish between and explain how pollen and spore evidence can be used in crime investigation