Arguably, the most important person at a crime scene is the first officer to arrive. The first responding officer often makes or breaks a crime scene. The manner in which he/she initially handles a crime scene can dictate how things go in the overall investigation. The journey from crime to conviction begins when the first responding officer arrives.
First responders to crime scenes are a crucial part of any criminal investigation. The first officer at the scene has many responsibilities including:
Establishing the perimeter of the crime scene
Determining where the suspect(s) entered and exited
Keeping unauthorized people out of the crime scene
The first officer at the scene walks a fine line regarding their actions at a crime scene. Upon arrival, crime scene investigators (CSI’s) would like to be provided a general idea of what occurred, but at the same time, they do not want an officer to disrupt the crime scene.
Even with limited knowledge of evidence and its preservation, a police officer or security officer, who is the first responder to a crime scene can properly protect, preserve, and, in some cases, collect evidence.
The officer who is the first to arrive at a crime scene must appreciate the importance of preventing or controlling any changes in the crime scene. The two critical factors most likely to change the crime scene are people and the weather. The first factor is the most amenable to officer control.
First, the officer must ensure that he/she does not introduce change into the crime scene. The patrol car should be parked away from the crime scene, both to prevent impacting evidence left by the suspect and to prevent any suspect still on the scene from observing the officer. Officer and citizen safety are of primary concern when entering a possible crime scene, even if it may mean compromising some evidence. The search for a perpetrator may inevitably involve officers' leaving some of their own trace evidence at the crime scene. While making a search, officers should limit touching objects and places at the scene.
Generally, the first officer at the scene should not attempt to collect evidence. However, there are some situations that may warrant evidence collection before CSI’s arrive. For example, if a victim has attempted suicide with a firearm, Emergency Medical Services (EMS), or the first officer at the scene, will need to remove the weapon from the victim’s grip for safety reasons and to provide medical care if still possible.
Should it be evident that there is a possibility of rain, the first responding officer should do everything possible, including using shoe boxes, tarps, plastic etc to protect any evidence such as spent bullet casings, blood stains, tire tracks, boot/shoe prints etc.
Remember that you can never take too many photographs of a crime scene.
Another concern regarding the preservation of the crime scene is the alteration of electronic devices. Officers should avoid handling and scrolling through computers or cell phone applications. Often times at a homicide or suicide scene, first officers become curious when they see computers and decide to jiggle the mouse to see what is on the screen or even attempt to view the search history. By simply moving the mouse or turning a computer or smartphone on or off can contaminate the electronic evidence. The electronic device may hold key evidence and should only be examined by a trained computer forensics investigator.
When it is clear that the scene poses no danger, the first responding officer should cordon off any area of the scene likely to contain evidence from the crime. This can be done with crime-scene tape and the posting of one or two officers at strategic spots. No unauthorized personnel, including police officers, should enter the scene. A log must be kept of everyone entering and exiting the crime scene. This serves two purposes, it ensures only authorized personnel enter the scene and should exclusion fingerprints and shoe/boot prints etc be required the investigators will know who to contact.
In securing the scene, officers should be careful to observe and avoid disturbing any possible evidence. The names of possible witnesses should be obtained, but officers should avoid interviewing a witness or suspect at length. This should be left to follow-up investigators. First-responding officers should document in writing every action and movement that they take, keeping in mind that this is likely to be the subject of any examination and cross-examination should a trial occur.
When securing the crime scene two perimeters should be set up, the outermost perimeter should be demarcated with yellow crime scene tape and the inner perimeter should be demarcated with red crime scene tape. The outer perimeter keeps out all unauthorized personnel, neighbors, media and other citizens; the inner perimeter demarcates the actual crime scene. The area between the outer and inner perimeters would be the staging area for the authorized personnel. Crime scene investigators can park their vehicles and set up their field lab.
The first responding officer holds a tremendous amount of responsibility not only for the crime scene but also for the overall investigation and ultimately the prosecution of the case. He/she needs to know his her limits and capabilities – and when to call other agencies with the right expertise.