POLLEN AND SPORE EXAMINATION

INTRODUCTION

Pollen and spore information can be used to determine the following: Was the body moved? Where did the crime take place? What season did the crime take place? Did the crime take place in the day or night?

Forensic Palynology – study of pollen and spore evidence to help solve a crime.

Pollen – reproductive structure that contains sperm from seed plants

Spore – reproductive structure that develops into an adult in algae, some plants, and fungi.

POLLEN PRODUCERS

Pollen “fingerprint” – number and type of pollen grains found in an area at a particular time of year.

Plant kingdom is divided into two groups based on how they reproduce: seeds or no seeds. Seeds: Gymnosperms (evergreens) and

Angiosperms (flowering plants) Nonseeds: Ferns, moss, liverworts, horsetails,

club mosses

GYMNOSPERMS Means “naked seed” – the seed is not

protected like they are in flowering plants Most numerous group of gymnosperms are

the conifers (evergreens) Produce their seeds within a cone. Here’s

how: Pollination occurs when pollen lands on a female

cone, grows and releases the sperm near the egg.

Once the egg is fertilized, a seed develops (containing an embryo)

ANGIOSPERMS Flowering plants Produce seeds within an enclosed fruit Parts of a flower:

TYPES OF POLLINATION

Important in forensics in determining the presence or absence of pollen in a place or on an object of a crime scene

Self pollination vs. Cross pollination Self – pollen transfer from anther to stigma

within the same flower. Cross – pollen transfer involving two distinct

plants Self pollinating plants has lower value because

they produce less pollen

METHODS OF POLLINATION

Wind pollination – produce a lot of pollen (good and bad) Good – well represented in the pollen profile of a

crime scene Bad – less effective in determining direct links Flowers are usually nonfragrant, lack color, small

Animal pollination – insects, birds, bats, monkeys Flowers are fragrant and “showy” Pollen grains are durable and can adhere to things Strong evidence of contact Produce less pollen

Dandelion – wind pollinated

Burs – animal pollinated (poor dog)

Notice the hooks on the ends of the spikes

Maple tree seeds – “helicopters”

METHODS OF POLLINATION CONTINUED

Water pollination Rarely preserved because it is composed of only

a single layer cell wall made of cellulose Pollen will decompose if removed from water Limited use, excepts for drowned victims…

contents of the lung can be emptied and analyzed.

SPORE PRODUCERS

Algae Adapted for dispersal in water or air

Ferns and Mosses Release spores into the air Because of this, forensics is most interested in these

Fungi Produce a large amount Mold, yeast, mushrooms Can be found practically everywhere

Bacteria (an exception) Some bacteria produce thick-walled, resistant spores

called endospores. Different in structure and aren’t used in reproduction Bacteria that causes anthrax and botulism are examples

SPORE DISPERSAL Wind Water Spore ejection Animal disperal (they eat the spore and

deposit it somewhere else in their feces)

Spore analysis has one advantage over pollen…it is possible to grow the organism and identify the species exactly.

POLLEN AND SPORE IDENTIFICATION IN SOLVING CRIMES

Exine -- The hard outer layer of a pollen or spore grain Has a unique and complex structure under the

microscope. Larger pollen grains can’t travel far (can only

drift with the wind ½ mile) (corn) Wind-dispersed pollen grains are simple,

have thin walls, easily preserved Animal-dispersed pollen grains are large,

sticky, highly ornamented, thick-walled and easily preserved

POLLEN AND SPORE IDENTIFICATION IN SOLVING CRIMES CONTINUED

Identification of pollen and spore grains is species specific Help determine season Help determine location If not native to the crime scene, body was

moved. Pollen and spores are difficult to eliminate by

the suspect because they are microscopic They are resistant to dehydration and

decomposition (can be found in sediment from millions of years ago)

Locard’s principle is easily applied (especially animal dispersed seeds)