PAST CRIMESEurope, perhaps Switzerland) but also changes in subsistence strategies and
diet in ancient populations, such as the adoption of farming.
Archaeological prospection is another area that is applied to forensics.
Prospection methods are used to find sites beneath the ground. They are
known to followers ofTime Teamas“Geofizz”. The mechanical methods
include magnetometry, which measures changes in magnetic responses in the
ground; resistivity which records variations in the ability of the soil to conduct
electricity; ground penetrating radar; metal detectors; and Lidar (Light
Detection and Ranging). Other forms of prospection include land survey,
aerial photography and soil sampling. Each method has its own strengths–
magnetometry identifies areas where heat has affected the background level of
the earth’s magnetism, and so indicates the presence of hearths or structures
made of fired brick among other things and it can identify areas of ground
where there has been disturbance. Resistivity can be used to produce a map of
walls and ditches hidden under the ground, based on the amount of electricity
received back from a probe passed over the earth; loose damp structures like
ditches will send back more of the current than hard dry ones such as walls
and floors. It can also record the difference in electrical current in the ground
where a body is present. Ground penetrating radar (GPR) machines send
pulses of electromagnetic radiation into the subsoil and record the signals
received back from structures beneath. GPR has been used to find bodies
buried in concrete. Metal detectors, of course, find objects in the soil–
marvellous finds like the golden objects from the AngloSaxon period found
in Staffordshire, but also more mundane things like metal fittings from the
remains of buildings or coffins, or buttons and zips on buried clothing.
Both aerial photography and Lidar use aircraft to view the ground surface
from above. In the case of Lidar, a pulsed laser beam is scanned over the
survey area and can measure between 20,000 and 100,000 points per second.
A highly accurate plan of features that might be almost invisible at ground
level can be created by this method and, unlike aerial photography, can even
record traces of activity such as banks and enclosures in areas covered by
trees. Aerial photography has been a useful archaeological tool since the First
World War. From the air, changes in soil colour, cropmarks, the way water or
snow is lying across a site, and shadows cast by low sun can all be seen in a
way impossible at ground level. These marks can all indicate archaeological
features–buried ditches and structures which, although virtually invisible,
nevertheless reveal their presence when viewed from an aircraft.
Geophysical prospection has been used during many criminal
investigations, such as the Margate case mentioned earlier, in 1994 with the