How Crime Scene Investigations Work

Crime scene investigation is something that interests many Americans—it is no coincidence that television shows like “CSI: Crime Scene Investigation” are so popular and have been on for so many years. But unlike what is shown on television, crime scene investigations are not always full of drama, and can often be tedious and require hours of painstaking work to gather as much evidence as possible.

Anatomy of a Crime Scene

Typically the first people at the scene of a crime are police officers. If a suspect is still at the crime scene he or she will be arrested, and an ambulance will be called if the victim is still alive and needs medical attention. The police offers will then secure the scene to preserve important evidence.

Crime scene investigators are then called to the scene to collect evidence. Depending on the crime, this process can take hours or even days. Detectives often show up at the scene to speak with witnesses, if there are any, and consult with the crime scene investigators.

In the event of a murder, the medical examiner may be called to the scene to determine a preliminary cause of death. The CSI unit may also consult with forensic scientists and forensic psychologist if there is evidence that requires expert analysis.

Crime Scene Investigators and Forensic Scientists

The act of collecting evidence and processing a crime scene in the field is crime scene investigation. The evidence collected is then sent to a crime lab where it is analyzed by forensic scientists. While crime scene investigators do not use the same tools to analyze evidence as forensic scientists, it is important for crime scene investigators to have a strong background in forensic science to do their job well and recognize the value of different types of evidence. Successfully solving a crime and prosecuting the perpetrator relies heavily on crime scene investigators and forensic scientists.

Processing a Crime Scene

The CSI unit does not arrive on the scene and just start collecting evidence. Upon arriving, the crime scene investigators will ensure that the scene is completely secure and speak to the first responders to see if anything has been touched or disturbed.

The first step of a crime scene investigation is a thorough walk through so the crime scene investigators can get a feel for the scene, formulate theories based on examining the area visually, and note possible sources of evidence. Nothing is touched during the initial walk through.

Documenting the Crime Scene

After the walk through, the crime scene investigator will begin looking at evidence and documenting it through photographs. There are typically three types of photographs taken:

  • Overview: These include wide shot photographs of all rooms at a crime scene (not just the room where a body was found or a crime occurred), the exterior of the crime scene, spectators viewing the scene, and shots that show the building in relation to surrounding buildings.
  • Mid-Range: These types of photographs capture evidence in context, so the evidence can be seen in relation to what is around it and what part of the room it is located in.
  • Close-Ups: Every piece of evidence is photographed in close range. These photographs are typically taken with professional lighting equipment to ensure that they are as clear as possible.

Collecting Evidence

Crime scene investigators are carefully trained to recognize and collect a variety of different types of evidence. The most common types of evidence include:

  • Body fluids: blood, semen, saliva, and vomit.
  • Trace evidence: gunshot residue, broken glass, drugs, and unknown chemicals.
  • Hairs and fibers.
  • Impressions: fingerprints, footprints, tool marks.
  • Firearm and weapons: guns, knives, bullet casings, bullet holes.
  • Documents: suicide notes, diaries/journals, personal phone books.

If the crime involves a fatality the CSI unit will thoroughly examine the body either at the scene or at the morgue. The body will be thoroughly photographed and detailed notes about the body will be taken.
Evidence collected at the scene is then sent to the crime lab to be analyzed. The reports from forensic scientists are then sent to the detective leading up the investigation, and the evidence collected from the scene is used to discover who did the crime, and put him or her behind bars.