Crime Scene Investigation: Key Steps, Evidence & Procedures

Introduction to Crime Scene Investigation

Crime scene investigations revolve around safeguarding the crime scene, protecting physical evidence, and gathering and transferring evidence for scientific evaluation. This process is grounded in the role that physical evidence plays in the overall investigation and determination of suspected criminal activity. The ability of physical evidence to fulfill that role depends on actions taken early in the investigation process at the crime scene. In recent years, criminal investigation processes have been enhanced by technological developments in the examination and interpretation of physical evidence, placing greater emphasis on proper documentation and preservation. The ultimate significance of evidence obtained from a crime scene depends on investigations that are thorough, objective, and thoughtful. Crime scene investigations consist of several key processes, including controlling the crime scene, gathering and marking evidence, and documenting and submitting evidence.

The first step in crime scene investigations is approaching, arriving at, and controlling the scene in order to safeguard evidence that will help resolve a criminal matter ("A Guide for General Crime Scene Investigation," 2009). This process is usually carried out by initial responding law enforcement personnel and involves several steps: responding with caution, following safety procedures, providing emergency care, and securing and controlling people at the scene. Additional steps include identifying, establishing, protecting, and securing boundaries; transferring control of the scene to investigators; and documenting observations and actions.

Approaching and Controlling the Crime Scene

Law enforcement personnel who arrive at a crime scene must be methodical and cautious in their approach to protect physical evidence. These officers should seek to minimize contamination of the evidence. When approaching the scene, officers should remain alert and attentive, treat the site as a crime scene until it has been examined and determined otherwise, and note or log dispatch information. They should also make initial observations to assess their own safety, examine the scene, and take note of individuals and vehicles entering or leaving the location.

Approaching the crime scene also involves following safety procedures by identifying any harmful situations or individuals in order to keep themselves and the public safe. This means ensuring there are no direct threats to other responders and investigators, and using an approach that enhances the safety of victims and witnesses. Officers achieve this through a thorough scan of the scene for sounds, sights, and smells that indicate potential threats or danger. When victims or witnesses are injured, the initial responding officers should provide emergency care while minimizing contamination of the scene ("A Guide for General Crime Scene Investigation," 2009). This includes evaluating the medical needs of the injured, calling for medical personnel, guiding them to the scene, and recording the movement of individuals and items by medical personnel.

Scene safety is further ensured by securing and controlling all persons at the location. The first step is identifying everyone present, including suspects, witnesses, victims, bystanders, family members and friends, and medical and other assisting individuals. Suspects, witnesses, and victims should be secured and isolated from the rest; bystanders should be removed from the scene; and family members and friends should be managed through compassionate means. Officers must prevent people from interfering with or destroying evidence by limiting their movements and activities. Non-essential and unauthorized personnel — including the media — should be excluded from the scene because they are not working the case.

With respect to physical boundaries, law enforcement personnel should identify, create, safeguard, and secure scene perimeters. Boundaries should be expanded beyond the initial scope of the crime location, with the understanding that they can be reduced in size when necessary. Establishing these boundaries involves starting at the focal point and extending outward to encompass the site where the crime took place, probable entry and exit paths of suspects and witnesses, and locations where victims or evidence are found. Officers should also create physical barriers, document the entry and exit of all individuals, control the flow of people, record the initial locations of victims and any items that have been moved, and consider search and seizure requirements. It is equally important to prohibit activities within the boundaries such as chewing tobacco, eating, drinking, making phone calls, smoking, touching anything, spitting, littering, and moving items ("A Guide for General Crime Scene Investigation," 2009).

Transferring control of the scene to investigators and recording observations and actions are also critical steps. The transfer of control requires briefing the incoming investigators, assisting them in managing the location, formally transferring responsibility, and remaining on-site as needed. The documentation process involves recording the conditions upon arrival, actions taken by officers, and relevant personal information.

Although the media is among the unauthorized and non-essential personnel at a crime scene, managing media relations and broadcasting alarms is an important aspect of crime scene investigations. Effective relations between the media and law enforcement during an investigation help protect and safeguard physical evidence by preventing unintentional contamination. Media relations during crime scene investigations should be governed by the department's written policy, which provides measures for restricting unnecessary access to the scene. This policy is particularly necessary because initial responding officers may face challenges in protecting the scene from media interference.

Broadcasting Alarms and Media Relations

A clearly written policy provides a consistent framework for all stakeholders present at the scene (Garrison, n.d.). In addition to the policy, initial responding officers should designate a specific location for media personnel — one that is situated well outside the scene boundaries to prevent unintentional interference with physical evidence. Establishing a media relations area near, but not within, the crime scene helps officers maintain control and monitor activity in the surrounding area.

Broadcasting alarms are also crucial in this process as a means of promoting the safety of individuals at the scene. Broadcasting alarms allow the law enforcement department to know when personnel require immediate assistance, such as in a medical emergency. Initial responding officers may use broadcasting alarms to call for emergency services when the safety of individuals is at risk, to request backup or reinforcement, or to contact firefighters in the event of a fire.