The initial thoughts and efforts of the first responder must be directed to the welfare of the victim, and the safety and well-being of the first responder and others at the crime scene. As the responder investigates the crime scene, s/he is basically doing the first walk-through of the area; all activities must be mentally noted, and later reduced to detailed written notes, such as where the officer walked and checked to see if suspects were still at the scene. S/he must note weather conditions, whether windows and doors are open or closed, condition and type of lighting, if appliances such as televisions or radios were on or off, angle of the sun or moon, and other conditions that may be needed to accurately reproduce the scene in a court trial.

Depending on the type of crime involved, the officer must determine if the victim is alive or injured. If the victim is dead, the body is not generally moved except by the medical examiner. When the victim is injured, the officer must immediately call the paramedics and render first aid as needed. Isolation and protection of the scene is necessary, but the preservation of human life is a priority. By the very nature of their work, paramedics will usually turn a crime scene into a mini-ER. Supervisors, crime scene technicians, detectives and other official personnel must be notified, and will be disruptive to the crime scene. As visitors arrive, it is crucial that the officer continue to protect the scene, by limiting entry into the ribboned-off area, and keeping a written record of who arrived and when. It is said by many homicide detectives, that a criminal cannot enter an area, without leaving a trace of evidence that s/he was present, which of course, will also include traces of information left by legitimate investigating personnel (e.g., hair, thread and fibers).

Witnesses pose their own set of special problems. The officer must never forget that "the so-called witness" might also be a suspect, and may want to re-enter the crime scene to erase evidence and/or generally contaminate the area. Witnesses should be separated and interviewed whenever possible in a private, secure area.  Neighbors and other well-wishers may enter the crime area with good intentions, and yet, contaminate the area by handling evidence or stumbling over vital clues.

The first responder must be careful to wear protective clothing, especially gloves, when processing any type of human fluids, in view of recent disease developments and OSHA requirements. It is also important not to leave ·additional evidence· at a crime scene by the first responder such as his/her footprints in blood or fingerprints in various parts of the location. If the officer accidentally contaminates the scene, then this information should be clearly noted in the reports.

The officer must point out vital evidence to the evidence technicians and detectives so that nothing is inadvertently overlooked. The other participants, e.g., the evidence technician, also has the responsibility to keep the primary officer informed, and let him know if obvious errors are being made. The evidence log must be maintained and nothing should be removed from the crime scene area without a clear written entry as to who found it and where. This information will later be entered in the Department's Property Book/Evidence Log, and will note a clear chain of custody, especially for items that are slated to go to the criminalistics laboratory for analysis.

The crime scene must be protected until all possible evidence, testimony from witnesses and nearby residents, photos (still and video), prints and sketches are collected and completed. Recent court cases have placed new requirements on crime scenes and detectives, in that once the investigators leave a crime scene for whatever reason, then lithe right of privacy" reverts to the property owner, and a search warrant might be necessary to legally reenter the scene for follow-up.

In summary, the first responder's reports must include his/her observations, the overall condition of the crime scene, and all evidence pertaining to the crime. The strict, detailed maintenance of the evidence will guarantee the most correct and truthful information available to the court, and it must be preserved in its natural state, free from alteration and contamination. And finally, no evidence should be disposed of until the case is terminated by the courts, including appeal, or the finest efforts of the first responder to the crime scene will be for naught.