A Behind-the-Scenes Look at Forensic Science: What Happens at a Crime Scene?

Crime scene investigation (CSI) is a lot more complicated than what you might see on television. In many mystery shows, the investigators show up, take a few photographs, and then return to the lab to conduct experiments. Although these shows make for great entertainment, they don’t depict the planning, time, and effort that go into real crime scenes. Every crime is an event that must be managed and reconstructed through isolating the area, documentation, and organization. To accomplish this task, crime scene investigators must follow certain procedures. Keep in mind that precincts vary in their duties depending on available staff, and the scope of the crime may or may not involve various departments or organizations such as the local police, forensics experts, or national organizations such as the Federal Bureau of Investigation (FBI). With that in mind, the following procedures are standard across the board.

The Initial Call

When someone notifies authorities about a crime, the first responders who arrive need to determine the scope of the crime and to isolate the crime scene in what is known as a “core area.” The scope of the crime can help to determine the number of people or organizations that need to be involved in the investigation.

1. Isolating the crime scene is imperative to determine how the crime occurred. The first individuals at the crime scene should secure the scene and act as security to restrain people who do not need to be at that location. Contamination of evidence jeopardizes the case, so management of this scene is imperative.


2. Further personnel are then contacted if required. A minor accident or damages to property may not require any other personnel. Fatalities, however, may call for supervisors, forensics teams, photographers, and medical personnel.


3. Witnesses are isolated and other people are removed from the crime scene after noting names and contact information.


4. If allowed, certain evidence such as shoeprints or gunshot residue should be collected immediately; otherwise, this fragile evidence can easily be destroyed or lost. Outside this collection, it is advised that first responders don’t touch anything, unless there’s an injured person.


5. If injured people are involved in the scene, an officer may accompany that injured person to the hospital in an ambulance once backup personnel arrive.

Managing the Crime Scene

It is impossible for a suspect and victim to come together in a violent manner and not leave evidence at a crime scene. After first responders initially determine the parameters of the crime scene’s core area, that scene may expand or contract depending upon evidence found at the scene. It is easier to contract a scene than it is to expand it. A crime scene also can encompass access and escape routes, other locations away from the initial scene, and vehicles used in a crime. For a complete and thorough examination of a crime scene, the following might take place:

1. Once investigators or initial responders create a secure core area, they may get the district attorney involved. If anyone could possibly have expectations of privacy in any portion of that crime scene, the CSI team will need search warrants. Since any evidence may be used in court, the search warrant can protect any collection of that evidence.


2. Outside the team leader, a crime scene may require the skills of photographer, sketch artist, evidence recorder, and other team members who will record evidence at the scene. This includes photographing and sketching bodies and the entire surrounding environment, and taking intricate notes about the scene and including all information, even if it doesn’t seem relevant at the time.


3. The investigators, hopefully, will use a predetermined path that is least likely to contaminate any possible evidence at that scene. Using all senses, details are noted such as smells, sounds, weather, lights on or off, furniture or other items that appear to be in unusual places, etc.


4. CSI team leaders usually create logs to record time of events and discovery of information, as well as individuals who enter and leave the crime scene during an investigation. Witness interviews also are noted and/or recorded; however, witnesses also may be interviewed again at a police station.


5. Sometimes, if police or investigators plan to be at a scene for a long time, a command post is designated. At a professional crime scene, a “safe area” always is designated to keep personnel away from the scene and to avoid contaminating evidence.


6. It is in this safe area that CSI teams can interview first responders, witnesses, etc., and to call in other experts as needed. Only experts at interviewing should interview witnesses and other crime scene participants.


7. If a forensics team is not in charge of the evidence, the name of the single officer who collects evidence should be noted. Designating one person to collect evidence helps to eliminate the possibility of lost or misplaced evidence. All personnel should wear gloves.


8. Physical evidence is taken to laboratories for further assessment. The scene also should be dusted for fingerprints, but only after all photographs and other evidence have been recovered and/or removed.

Arrival of ME or EMT

The arrival of a medical doctor, coroner, or other medical personnel deemed responsible for the removal of bodies usually marks the end of a crime scene investigation. However, this is a crucial time of crime scene study.

1. Before the ME (medical examiner) arrives, all photographs of the surrounding environment should be completed, as well as any sketches of the crime scene.


2. The arrival of an ME signals that photographers and forensic experts may now collect more evidence, as new portions of the body not visible prior to the ME’s arrival now can be documented. The ME at this point may examine the victim and pronounce the victim dead at the scene with determination of cause and time of death. If this determination is not possible, the victim’s location and position of the body are marked, and the body is removed from the scene for further examination.


3. The preservation of the body in transit is marked by covering with a sheet and placement in a body bag. Paper bags on the hands can preserve any trace evidence under fingernails.

Crime Scene Reconstruction

Every crime and crime scene is different. The investigation of a mass murder is much different than the investigation of an accident. In some cases, a crime can be reconstructed at the scene, depending upon the information and evidence gathered. In other instances, a crime scene may take months to reconstruct.

During the reconstruction phase of crime scene investigation, more theories of a crime are developed or disregarded based on the found and collected evidence. When forensic scientists test the evidence, the accuracy of these theories is tested and validated or disproved.

Even if the reconstruction is not complete at the crime scene, the person in charge of the scene may release the scene if all evidence has been gathered. In some cases, no one will be able to subsequently enter the crime scene unless a warrant is obtained. This may hold true especially in cases where the reconstruction of the crime scene is undetermined.

The truth is present at every crime scene. A small rural area may not follow all the steps or use as many people in their investigations as a large city. Additionally, the scope of the crime indicates how many people and how much paperwork might be involved. In all cases, however, documentation is imperative. Without a trail of evidence, criminals may never be convicted.