Evidence collected at a crime scene must be properly preserved. Secure and preserve the crime scene. Before any evidence can be collected, the scene must be secured from further contamination. Establish a crime scene perimeter and allow only necessary personnel to enter. Photograph the scene before evidence is collected.
The procedures consist of collecting the evidence using the correct tools and equipment, bagging the evidence in an appropriate manner and also tagging and labelling the evidence correctly. These procedures guarantee that evidence is preserved correctly and is not contaminated prior to it being forensically examined.