Once a crime scene has been established it is important that all evidence is collated, catalogued and recorded for further reference. This task is normally performed by the Scenes of Crime Officer (SOCO) and is carried out using a variety of methods.
Methods of Preserving and Recording
Evidence that is loose and perhaps lying on the ground should be bagged up and catalogued; each piece of evidence is given an individual identification number so that it can be cross-matched against corresponding investigative reports. The evidence is bagged in clear plastic bags, which are sealed airtight so that no contamination can take place.
Each of these bags is accompanied by a ‘custody chain’ document; this document is to be filled out by any officer who wishes to use or view the evidence. This is necessary to reduce the loss of evidence and/or cross contamination by individuals who should not have contact with it.
The area is photographed in meticulous detail and any signs of injury such as bloodstains are marked, numbered and photographed. These photographs are often important in the piecing together of an event so that officers who were not able to attend the scene can get an understanding for how it looked. Nowadays with the advent of technology digital technology such as video cameras are also used to record the nature of the scene. SOCO may also make audio recordings as to their findings while they go.
Fingerprints are taken where possible and if the crime scene is outdoors the area is marked out and searched; these searches can take the form of a linear search (a single row of officers moving in unison in a straight line), a grid search (a single row of officers moving in unison in a series of squares), a quadrant search (one officer is allocated a particular area of ground to search) or a spiral search (officers start from the middle of the crime scene and work their way outwards in a spiral pattern so as to identify possible pieces of evidence that have spread further than the crime scene itself.
Soil samples are also taken as the chemical make up of soil will vary from place to place; a corpse may have soil on the soles of their feet or under their fingernails, which may not have been gathered at the location where the body was found.
It is sometimes necessary for dogs to be used at a crime scene; this is done so that evidence that may not be visible to the naked eye can be detected.
Internal crime scenes are photographed, blood spatter patterns are measured and documented, and bloodstains on carpets and floors are measured for radius.
Regardless of the location of a crime scene it is imperative that all of those personnel involved in the recording and preserving of it are dressed correctly in protective clothing. This clothing which normally takes the form of plastic trousers and jacket; protective hat (to minimise the possibility of the hair of those personnel investigating; contaminating a scene), and shoe covers which are used to reduce the risk of bringing materials from other locations to the scene of the crime.