"CSI: Crime Scene Investigation" Who Are You (2...
On TV shows like "CSI," viewers get to watch as investigators find and collect evidence at the scene of a crime, making blood appear as if by magic and swabbing every mouth in the vicinity. Many of us believe we have a pretty good grip on the process, and rumor has it criminals are getting a jump on the good guys using tips they pick up from these shows about forensics.
"CSI: Crime Scene Investigation" Who Are You (2...
But does Hollywood get it right? Do crime scene investigators follow their DNA samples into the lab? Do they interview suspects and catch the bad guys, or is their job all about collecting physical evidence? In this article, we'll examine what really goes on when a CSI "processes a crime scene" and get a real-world view of crime scene investigation from a primary scene responder with the Colorado Bureau of Investigation.
Crime scene investigation is the meeting point of science, logic and law. "Processing a crime scene" is a long, tedious process that involves purposeful documentation of the conditions at the scene and the collection of any physical evidence that could possibly illuminate what happened and point to who did it. There is no typical crime scene, there is no typical body of evidence and there is no typical investigative approach.
Joe Clayton is a primary crime scene responder at the Colorado Bureau of Investigation (CBI). He has 14 years of field experience and also is an expert in certain areas of forensic science. As Clayton explains, his role in laboratory analysis varies according to the type of evidence he brings back from the crime scene:
When a CSI arrives at a crime scene, he doesn't just jump in and start recovering evidence. The goal of the scene recognition stage is to gain an understanding of what this particular investigation will entail and develop a systematic approach to finding and collecting evidence. At this point, the CSI is only using his eyes, ears, nose, some paper and a pen.
The first step is to define the extent of the crime scene. If the crime is a homicide, and there is a single victim who was killed in his home, the crime scene might be the house and the immediate vicinity outside. Does it also include any cars in the driveway? Is there a blood trail down the street? If so, the crime scene might be the entire neighborhood. Securing the crime scene -- and any other areas that might later turn out to be part of the crime scene -- is crucial. A CSI really only gets one chance to perform a thorough, untainted search -- furniture will be moved, rain will wash away evidence, detectives will touch things in subsequent searches, and evidence will be corrupted.
Usually, the first police officers on the scene secure the core area -- the most obvious parts of the crime scene where most of the evidence is concentrated. When the CSI arrives, he will block off an area larger than the core crime scene because it's easier to decrease the size of a crime scene than to increase it -- press vans and onlookers may be crunching through the area the CSI later determines is part of the crime scene. Securing the scene involves creating a physical barrier using crime scene tape or other obstacles like police officers, police cars or sawhorses, and removing all unnecessary personnel from the scene. A CSI might establish a "safe area" just beyond the crime scene where investigators can rest and discuss issues without worrying about destroying evidence.
Once the CSI defines the crime scene and makes sure it is secure, the next step is to get the district attorney involved, because if anyone could possibly have an expectation of privacy in any portion of the crime scene, the CSI needs search warrants. The evidence a CSI recovers is of little value if it's not admissible in court. A good CSI errs on the side of caution and seldom searches a scene without a warrant.
With a search warrant on the books, the CSI begins a walk-through of the crime scene. He follows a pre-determined path that is likely to contain the least amount of evidence that would be destroyed by walking through it. During this initial walk-through, he takes immediate note of details that will change with time: What's the weather like? What time of day of day is it? He describes any notable smells (gas? decomposition?), sounds (water dripping? smoke alarm beeping?), and anything that seems to be out of place or missing. Is there a chair pushed up against a door? Is the bed missing pillows? This is also the time to identify any potential hazards, like a gas leak or an agitated dog guarding the body, and address those immediately.
The CSI calls in any specialists or additional tools he thinks he'll need based on particular types of evidence he sees during the recognition stage. A t-shirt stuck in a tree in the victim's front yard may require the delivery of a scissor lift to the scene. Evidence such as blood spatter on the ceiling or maggot activity on the corpse requires specialists to analyze it at the scene. It's hard to deliver a section of the ceiling to the lab for blood spatter analysis, and maggot activity changes with each passing minute. Mr. Clayton happens to be an expert in blood spatter analysis, so he would perform this task in addition to his role as crime scene investigator.
During this time, the CSI talks to the first responders to see if they touched anything and gather any additional information that might be helpful in determining a plan of attack. If detectives on the scene have begun witness interviews, they may offer details that point the CSI to a particular room of the house or type of evidence. Was the victim yelling at someone on the phone a half-hour before the police arrived? If so, the Caller ID unit is a good piece of evidence. If an upstairs neighbor heard a struggle and then the sound of water running, this could indicate a clean-up attempt, and the CSI knows to look for signs of blood in the bathroom or kitchen. Most CSIs, including Mr. Clayton, do not talk to witnesses. Mr. Clayton is a crime scene investigator and a forensic scientist -- he has no training in proper interview techniques. Mr. Clayton deals with the physical evidence alone and turns to the detectives on the scene for any useful witness accounts.
The CSI uses the information he gathers during scene recognition to develop a logical approach to this particular crime scene. There is no cookie-cutter approach to crime scene investigation. As Mr. Clayton explains, the approach to a crime scene involving 13 deaths in a high school (Mr. Clayton was one of the CSIs who processed Columbine High School after the shootings there) and the approach to a crime scene involving a person who was raped in a car are vastly different. Once the CSI has formed a plan of attack to gather all of the evidence that could be relevant to this particular crime, the next step is to fully document every aspect of the scene in a way that makes it possible for people who weren't there to reconstruct it. This is the scene-documentation stage.
The goal of crime-scene documentation is to create a visual record that will allow the forensics lab and the prosecuting attorney to easily recreate an accurate view of the scene. The CSI uses digital and film cameras, different types of film, various lenses, flashes, filters, a tripod, a sketchpad, graph paper, pens and pencils, measuring tape, rulers and a notepad at this stage of the investigation. He may also use a camcorder and a camera boom.
Note-taking at a crime scene is not as straightforward as it may seem. A CSI's training includes the art of scientific observation. Whereas a layperson may see a large, brownish-red stain on the carpet, spreading outward from the corpse, and write down "blood spreading outward from underside of corpse," a CSI would write down "large, brownish-red fluid spreading outward from underside of corpse." This fluid might be blood; it might also be decomposition fluid, which resembles blood at a certain stage. Mr. Clayton explains that in crime scene investigation, opinions don't matter and assumptions are harmful. When describing a crime scene, a CSI makes factual observations without drawing any conclusions.
CSIs take pictures of everything before touching or moving a single piece of evidence. The medical examiner will not touch the corpse until the CSI is done photographing it and the surrounding area. There are three types of photographs a CSI takes to document the crime scene: overviews, mid-views, and close-ups.
Scene documentation may also include a video walk-through, especially in major cases involving serial killers or multiple homicides. A video recording can offer a better feel for the layout of the crime scene -- how long it takes to get from one room to another and how many turns are involved, for instance. Also, once the investigation is further along, it may reveal something that was overlooked at the scene because the investigators didn't know to look for it. During a video walk-through, the CSI captures the entire crime scene and surrounding areas from every angle and provides a constant audio narrative.
The goal of the evidence-collection stage is to find, collect and preserve all physical evidence that might serve to recreate the crime and identify the perpetrator in a manner that will stand up in court. Evidence can come in any form. Some typical kinds of evidence a CSI might find at a crime scene include:
With theories of the crime in mind, CSIs begin the systematic search for incriminating evidence, taking meticulous notes along the way. If there is a dead body at the scene, the search probably starts there.
A CSI might collect evidence from the body at the crime scene or he might wait until the body arrives at the morgue. In either case, the CSI does at least a visual examination of the body and surrounding area at the scene, taking pictures and detailed notes.
The zone search: In a zone search, the CSI in charge divides the crime scene into sectors, and each team member takes one sector. Team members may then switch sectors and search again to ensure complete coverage. 041b061a72