Criminal cases begin with a preliminary investigation conducted by the first law enforcement officials on the scene. There are basic steps to follow to ensure the safety of police personnel and the public. Protocol, appropriately followed, also provides protection of rights for all involved: victims, emergency responders, and suspects. A solid court case is founded on a clean and thorough investigation.
Upon approaching the scene of a reported crime, the first step is for the responding officer to assess the current situation. If the crime is still in progress the officer will need to determine who is a suspect and who is a victim, as well as gauge whether or not a threat still exists. If a threat is perceived, the threat must be neutralized before any investigation can begin.
As the wary officer arrives at the scene and begins the triage, they quickly determine what type of assistance is necessary (increased police presence, medical assistance, fire fighters) and what type of priority there is for that assistance. The officer needs to obtain control of the scene to ensure safety and protect the scene for evidence gathering. In a safe situation, the officer might proceed with crowd control before collecting evidence. In the case of victims needing first aid, the officer might first respond in that manner.
When the scene is under control, the officer must determine if a crime has been committed, and if it has, what type of crime. Initial scanning of the scene can help the officer to know the answers to those questions as well as help to identify suspects, witnesses, and evidence. The officer should also be aware of possible secondary crime scenes.
The next step is for the officer to develop a plan of action. Depending on the situation and location, this process might be accomplished by the responding officer alone, with other officers, or with department leadership, depending on the chain of command. The plan of action will help maintain order at the scene of the crime and direct in the apprehension of the suspect if they are at large.
Initial evidence is gathered; this could be accomplished through photographs, sketches, video, or speaking with victims and eye witnesses. The priority should be obtaining information regarding the suspect if they have not been apprehended. During this stage of investigation the officer will look for how the suspect entered and exited the scene of the crime and try to determine the location and magnitude of the crime.
Identifying a suspect is of primary importance. Suspect descriptions should be compiled and dispersed through police dispatch as soon as possible to aid in apprehension. Descriptions should have as much information as possible. Multiple witness descriptions are ideal as stressful situations make it difficult for people to remember minute details with accuracy.
Apprehension of the suspect is vital to any investigation. The most successful apprehension is one that is done at the scene as it concretely links the suspect with the crime. If the suspect isn’t apprehended until later, the arrest will have to depend on further evidence obtained at the scene or witness reports.
Thorough crime scene processing is the last step of the preliminary investigation. All aspects of the scene must be documented to allow further investigation to recreate the scene. Every bit of material in the perimeter of the scene must be identified and documented. Even the most remote and obscure items might have valuable information linking the suspect to the crime.