Regardless of the type of case the crime analyst will be engaged to dissect, the basis of any examination will usually begin with the physical evidence. This evidence could be in the form of biological material such as blood, saliva, or semen, or it could be marks and impressions left by tools or firearms. The examination of this evidence should only be conducted by the appropriately qualified individual, and with physical evidence this will likely fall to a forensic scientist. This is especially true of different types of crime reconstruction, although sequential reconstruction, the placing of events into a time-ordered sequence, can be done by virtually anyone. This chapter discusses some of the more common types of physical evidence before moving on to describe various types of crime reconstruction and then closing with considerations of crime scene security and processing.