By Jean Reynolds

Police actions at a crime scene fall into four categories: safety issues, preserving the crime scene, collecting evidence, and documenting the situation. Much that is critically important must be completed in the early minutes of the crime response.

The first person to arrive—often a patrol officer—must assess the situation and act quickly. One priority is assessing the need for medical assistance and arranging for medical help. Another is calling for assistance—usually a crime response team and additional officers. A third priority is protecting the evidence at the crime scene. The fourth is issuing information if a suspect is still at large—especially urgent if there’s a threat to public safety.

In the critical first moments, caution is essential. Even if the scene looks quiet, assume the crime is still in progress. Do not take unnecessary risks. Officers should also be aware that curiosity seekers who might compromise important evidence. It’s also important to realize that bystanders may be paying close attention to your actions and demeanor. Resist the impulse to use humor to ease any tension you may be feeling.

Here are some practical guidelines for responding to a crime scene:

  1. Safety issues

Even a crime scene that seems quiet and routine may harbor dangers:

  • Proceed cautiously until you’re sure the location is safe.
  • Assess any victims and call for medical assistance if needed.
  • Issue a description of the suspect if there’s danger to the public.
  • Be aware of potential hazards, such as pathogens, gasoline, and drugs.
  • Use safe procedures when dealing with biological samples.
  1. Scene preservation

It’s not enough to keep bystanders away from the crime scene. Even trained law enforcement and medical personnel may inadvertently compromise evidence if they’re not careful:

  • Ask medical personnel to preserve the victim’s clothing. If it needs to be cut, ask personnel to preserve bullet holes and knife tears if possible.
  • Use yellow tape to create a pathway for essential personnel at the crime scene.
  • Limit the number of official visitors to the scene. You don’t have to admit every EMT and law-enforcement official who offers to help.
  • Set up a staging area for media reporters.
  • Don’t handle evidence unless you’re a trained technician.
  • Remember that even small details can be important. Don’t adjust the thermostat, open windows or doors, or move any objects.
  • Don’t use the bathroom, telephones, or trash containers.
  • Don’t smoke at the scene. Odors can be important evidence, especially if a canine is involved in the investigation.
  1. Evidence collection

Although technicians usually collect and log evidence, patrol officers who arrive early at the crime scene can play an important role in the investigation:

  • Consider asking a patrol officer to ride in the ambulance with a victim—it may be the only opportunity to get testimony from someone who was seriously injured.
  • Take pictures of the victim’s condition and clothing, since they may prove important in a jury trial.
  • Consider bagging the suspect’s hands to preserve any gunshot residue or evidence that the victim struggled.
  • Consider asking the victim or suspect for consent to search the premises or initiating the process for obtaining a search warrant.
  1. Documenting the crime scene

Here again the patrol officer can play a vital role by starting a crime-scene log document the temperature, lighting, open doors and windows, odors, and other information about the crime scene. The log should also contain arrival and departure times for medical and law enforcement personnel.

All officers at the scene should record their actions and observations in detailed police reports.

The FBI has published a free and highly useful resource called Criminal Scene Investigation:

Technical Working Group on Crime Scene Investigation. (2000). Crime Scene Investigation. Retrieved November 29, 2015, from