Direct and Circumstantial Evidence
During a criminal investigation, there are two basic kinds of proof needed to establish the guilt or innocence of a suspect. One type of proof is direct evidence, and the other is circumstantial.
Direct evidence involves testimony by eyewitnesses who have information to offer about the crime through one of their five senses. That is, they have seen, heard, smelled, tasted, or touched something related to the crime and, perhaps, related to the suspect. There are two general categories of witnesses: those who come forward with the evidence willingly and those who are unwilling—or reluctant— witnesses. Circumstantial evidence, on the other hand, is evidence from which inferences can be drawn and include items such as physical evidence (Weston and Lushbaugh, 2006). Usually, circumstantial evidence includes weapons, blood, fingerprints, tool marks, documents, and dust, dirt, or other traces.
Standard operating procedure is for the first patrol officer at the scene of the crime to detain witnesses and other persons who might offer help. That officer must obtain adequate information about each witness or each person who may have information to contribute. That would mean getting names, addresses, and phone number so detectives can follow up. It also means getting a description of the perpetrator from witnesses and securing a more complete description of the facts of the crime. A canvass of the neighborhood or surrounding area may be undertaken by the initial officers on the scene or later by investigators.
Circumstantial evidence may be found at the scene and must be handled in such a way that the evidence is not compromised or contaminated. Any evidence found at the scene should be secured by the patrol officer or investigator.