diatoms can help to establish the environment at the time the context was
buried, and can sometimes indicate the activities occurring around it. Changes
in soil compaction due to digging will also help different plants to establish
themselves on the site, and if there is a body buried in the soil, the
decomposition will change the soil chemistry and encourage or discourage
certain plant species. Clues like these may help to find bodies buried in
wilderness areas, and can assist in identifying suspects, as in a case from New
Zealand where a woman was assaulted and her house burgled by intruders
who, when making their escape, brushed up against a flowering bush by her
back door. Police were able to establish the presence of the bush pollen in
large quantities on the suspects’clothing, helping them to proceed towards a
conviction.
An early use of this type of evidence occurred in 1816. A young servant girl
had been violently attacked and drowned in a shallow pond near Warwick.
Police found trace evidence in wet mud by the pond–footprints and an
impression of patched corduroy cloth, along with a scatter of grains of wheat
and chaff. They were able to match the cloth impression to the breeches of a
farmworker who had been threshing grain nearby.^3
Identification of wood and other plant materials can also be used to
establish where a piece of equipment or tool came from. If a handle, or other
piece of equipment, is made from a particular type of wood or fibre that is not
local, tracing its origin may lead to the place of manufacture, which in turn
may lead to identification of possible suspects known to have come from, or
visited, that area.
Fans of theCSItelevision dramas will no doubt be familiar with the study
of insects and their behaviour in criminal investigations. In the case of burials,
the presence of certain insects at particular stages of their life cycles can tell us
whether the body was exposed before burial, at what time of year or day, and
for how long. Temperature, climate, whether the body is inside or outside,
large or small, covered or uncovered, all affect the rate of decomposition.
During this process, various organisms are attracted to the body, including
bacteria, fungi and insects. Flies prefer a body that is relatively fresh, while
various forms of beetle move in as it dries out. Different species are likely to
arrive at a corpse at different stages of its decomposition. Samples of the soil
and materials in and around the grave must be carefully collected to preserve
this type of evidence, and contamination must be strictly avoided. Under
average conditions, flies will typically invade an exposed corpse within an
hour of death. Within a day, their eggs will hatch into larvae, which go
through further feeding and moulting stages until they are ready to pupate.
ARCHAEOLOGY, HISTORY, CRIME AND PUNISHMENT