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Crime scene investigators, sometimes referred to as CSIs, are individuals trained to study crime scenes. One of the main duties of a crime scene investigator is to secure and preserve the scene of a crime. A CSI is also usually responsible for crime scene photography, detailed notes and paperwork, and evidence collection and processing.
A crime scene investigator's duties begin as soon as he arrives at the scene of a crime. After surveying the area, he must determine the boundaries of a crime scene. These boundaries are sometimes encircled with crime scene or police ribbon, or tape.
A crime scene investigator will then try to keep the scene in the condition it was found. Any piece of evidence that is moved, removed, or even added can make solving a crime much more difficult. A fingerprint from a careless police officer or a moved object can cause serious setbacks in a criminal investigation. Investigators will usually try to keep as many people out of the scene as possible. They will also try to ensure that everyone follows the correct procedures, such as wearing latex gloves and not moving anything.
While walking around the scene, a crime scene investigator will also usually take photographs. The crime scene photography requirements will generally depend on the nature of the crime. If a murder was committed, for example, pictures of the victim would be necessary. Any other evidence, such as a murder weapon or broken items, will also be photographed.
Accurate measurements from a crime scene are very useful when a crime scene investigator sketches the layout of the crime scene. These sketches are important, since they can show things that a photograph can not. A blood trail leading to a victim who is around the corner, for example, can not clearly be captured by a camera.
Another important duty of a crime scene investigator is evidence collection. Some evidence, such as a dead body or ransom note, is large and can be seen with the naked eye. Other evidence may require a trained eye or special equipment to see or be collected. This type of evidence may include fingerprints, bodily fluids, shed skin cells, or tiny fibers or hairs.
When all of the evidence has been collected, a CSI must then either process it himself — depending on his area of expertise — or ensure that it reaches the right department to be processed. Fingerprints, for example, may be processed by one CSI, while another CSI analyzes bodily fluids. Studying and analyzing the evidence collected at a crime scene can help investigators determine how and when a crime occurred. Sometimes, it can also tell investigators who possibly committed a crime.
Although often glorified as an action packed and exciting career, being a crime scene investigator often involves an enormous amount of paperwork. Notes must be taken during each stage of the investigation, from beginning to end. These are then usually put into reports. Additionally, paperwork must also be filled out every time evidence changes hands.
This is often known as a chain of custody of evidence, and it is an extremely important part of a criminal investigation. Keeping a detailed log of who handled any evidence can often make it hard for a defendant to prove that the evidence was contaminated or tampered with. This is especially important when a crime scene investigator is called to testify at a criminal trial.