The common types of physical evidence encountered at a property crime scene are trace, biological and comparative evidence. Assume that visible (blood, hair, etc.) or invisible (saliva, touch DNA, etc.) evidence may be left at every crime scene. The investigator should be aware of all types of biological evidence and the specific collection procedures used for each.
Biological evidence is subject to degradation from environmental factors. Maintaining safety and the integrity of evidence through preventative measures should include drying biological evidence and proper packaging.