Crime scene investigators operate as impartial scientific observers at the scene of a crime. Their function is not to solve the case, but to meticulously gather the physical facts that will be analyzed. They are specialists tasked with the identification, documentation, and collection of evidence. This work provides objective information, and their detailed efforts create a permanent record of the scene for any subsequent investigation or legal proceeding. This process demands a methodical and unbiased approach.
The Role of a Crime Scene Investigator
A Crime Scene Investigator (CSI), often a civilian professional or a specially trained sworn officer, is a specialist in evidence. Their primary objective is to systematically process a crime scene to locate, document, and collect any physical material that could be relevant to an investigation. This role is distinct from that of a detective, who is responsible for the broader investigation. Investigators are not involved in making arrests or interrogating suspects; their focus remains exclusively on the physical remnants of the event. They operate under the principle that every contact leaves a trace, searching for items such as fingerprints, DNA, fibers, and tool marks that can help reconstruct the incident.
Key Responsibilities and Duties
Securing the Scene
Upon arrival, one of the investigator’s first actions is to help establish and maintain the security of the crime scene. This involves ensuring the perimeter is large enough to contain all potential evidence and creating a log of every person who enters or exits the area. Controlling access prevents the contamination, destruction, or alteration of evidence. A single point of entry and exit helps investigators manage the scene and uphold the integrity of the materials they collect.
Documenting with Photography and Sketches
Documentation creates a permanent record of the scene as it was found. Investigators use comprehensive photography, taking overall, mid-range, and close-up shots of the area and each piece of evidence. These photographs are taken from various angles to capture spatial relationships, and a scale is included in close-up shots to provide a sense of size. This is supplemented by detailed sketches that include precise measurements, showing the location of evidence in relation to fixed points.
Searching for and Identifying Evidence
Investigators employ systematic search patterns to ensure the entire scene is examined thoroughly. Common methods include the grid, spiral, or strip/line search, with the choice depending on the size and nature of the location. They are trained to look for various forms of evidence, including latent prints, biological material like blood or hair, and trace evidence such as fibers or gunshot residue. Using tools like alternate light sources can reveal evidence not visible to the naked eye.
Collecting and Packaging Physical Evidence
Each type of evidence requires specific collection and packaging techniques to prevent contamination and degradation. Biological evidence, like a bloodstain, must be air-dried before being packaged in paper bags, as plastic can trap moisture and encourage bacterial growth that destroys DNA. Trace evidence might be collected with forceps or tape, while firearms are secured in boxes to prevent accidental discharge. Every item is placed in a separate, sealed container.
Maintaining the Chain of Custody
The chain of custody is the chronological paper trail that documents the life of every piece of evidence collected from the scene. This log details who handled the evidence, when they handled it, where it was stored, and why it was handled. An unbroken chain of custody is required for evidence to be admissible in court, as it proves the item presented is the same one collected at the scene and has not been tampered with or altered.
Essential Skills and Qualifications
Beyond technical knowledge, a crime scene investigator must possess a specific set of personal attributes. Meticulous attention to detail is a primary quality, as even the smallest oversight can compromise an investigation. Investigators must be methodical, following established procedures precisely to ensure the integrity of the evidence. Strong observational and analytical skills are needed to interpret what they see at a scene.
Objectivity is another core qualification. A CSI’s role is to collect facts, not to form opinions about guilt or innocence. They must remain detached and unbiased in their work. The job also demands significant emotional resilience, as investigators are frequently exposed to traumatic and disturbing scenes. The ability to remain calm and professional in such environments is necessary for effective work.
Education and Training Requirements
The path to becoming a crime scene investigator begins with a formal education. While some agencies may hire candidates with an associate’s degree, a bachelor’s degree is increasingly the standard. Common fields of study include forensic science, criminal justice, or a natural science such as biology or chemistry. A degree in a hard science provides a strong foundation for understanding the principles behind evidence analysis.
Formal education is supplemented by extensive hands-on training. New investigators often start in civilian roles or may come from sworn law enforcement positions. They undergo rigorous on-the-job training through police academies or specialized programs. Continuing education and certifications in areas like bloodstain pattern analysis or crime scene photography are common for career advancement.
Differentiating Fact from Fiction
Popular television shows have created a dramatized and often inaccurate perception of crime scene investigation. One significant misconception is the speed at which cases are resolved. On TV, DNA and fingerprint results are returned within hours; in reality, analysis can take days, weeks, or even months due to laboratory backlogs. This disparity has led to the “CSI effect,” where jurors have unrealistic expectations of forensic evidence.
Furthermore, television frequently portrays CSIs as all-in-one officers who process the scene, interrogate suspects, and make arrests. In the real world, these roles are distinctly separate. CSIs are specialists focused solely on evidence collection and analysis; interrogations and arrests are the responsibilities of detectives. The real job is far more methodical and team-based than the action-packed missions depicted on screen.
The Work Environment and Career Outlook
Crime scene investigators are employed by various government agencies, including local and state police departments, and federal agencies like the FBI. The work environment is highly unpredictable. Investigators are often on call 24/7 and must be prepared to work long, irregular hours in any condition, from extreme weather outdoors to cramped and sometimes hazardous indoor spaces.
The career outlook for forensic science technicians, which includes CSIs, is positive. The U.S. Bureau of Labor Statistics projects that employment in this field will grow faster than the average for all occupations, driven by the increasing reliance on forensic evidence. With experience, investigators can advance to supervisory roles like crime scene manager or specialize in a particular area of forensics.