PAST CRIMESidentifications of exact species in a particular place at a particular time. Vast
amounts of pollen are carried on the wind and settle on clothing and skin, and
are even inhaled as we breathe. In some cases, the types of pollen found at a
site can be very specific if they come from plants that are relatively rare, but
each part of the environment has its own population of plants, and thus its own
combination of pollens. The presence of some pollen grains can not only tell
us what plants were present, but sometimes even the time of year when an
event occurred, if the airborne pollen settled on the ground surface and was
then quickly buried. Most pollens are released during the summer or autumn
months, so finding a large amount of, say, wheat pollen in a grave would
suggest that the burial took place in the mid to late summer.
Pollen has been used in criminal investigations to determine the time of
year during which a body was buried. This can help to identify the victim by
comparison with the dates on which they were known to be still alive or when
they disappeared, and can also be used to check the alibis of suspects. If the
suspect was known to be a long way away at the season in which the pollen
could have found its way into the burial, then he is unlikely to be guilty.
Other plant remains can be equally useful–seeds, nutshells, algae and
Figure 1. Some pollen grain varieties