Palynology is a relatively new area of forensics but it has been instrumental in placing many criminals at crime scenes. In his book, Invisible Evidence, Bill O’Brien reports that the work is tedious but can be of enormous benefit in a homicide investigation. Because pollen is easily dispersed, it infiltrates into everything although it may not be seen with the naked eye.
Defining Pollen and its Characteristics
Pollen grains vary in size from about 3-5 microns to over 200 microns depending on the species. One micron measures one thousandth of a millimeter across. Pollen is mainly dispersed by wind but also by animals, insects and birds. Scientists are familiar with pollen dispersal patterns and will know if a certain type of pollen is generally carried far from the plant or dropped in the immediate vicinity.
If an unknown sample is provided, it is possible to determine what type of area it came from. This includes information such as whether the land was a swamp, heavily forested or covered in grass. If the pollen was found on a suspect’s clothing, it can point investigators to areas where the crime might have taken place.
Pollen varies from plant to plant and a mixture is often found at a crime scene. The first step to analyzing pollen is to place it under a microscope and magnify it up to 2000 times. Further analysis under a scanning electron microscope can enlarge a sample up to 50,000 times. In any given sample there may be as many as 200 different types of pollen but more commonly, around 60 to 100 types will be found.
If two people have been in the same environment, they will carry similar samples which will be a unique combination according to weather, season and time of day. Pollen grains are hardy, acid-resistant and almost impossible to destroy, making them a valuable tool in forensic analysis.
Where can Pollen Samples be Found
Pollen for analysis can be found in a number of places including the following:
· Clothing
· Soil
· Beneath fingernails
· Hair
· Just below the hairline on the forehead
·.
If pollen is collected from a body, a pathologist may retrieve it by swabbing deep inside the nasal passages which are accessed through the top of the head. From this type of sample, a palynologist can determine if the deceased took his last breath at the scene where the body was found. If a few pollen grains are found, the victim probably died standing up. Hundreds of pollen grains would indicate he died while lying on the ground where the concentration of pollen is much greater.
Pollen is useful in placing a suspect at a crime scene and can also be used to narrow the search for a missing body. It is almost indestructible and grains collected can be magnified and analyzed to reveal where a person died and what position they were in at the time. Samples are easy to collect but the process of analyzing them can be long and tedious.
Reference:
O’Brien, Bill, Invisible Evidence, David Bateman Ltd, 2007
