How to Examine a Crime Scene
Police take several deliberate steps when they investigate a crime scene. Those steps allow them to gather evidence in a thorough manner, and to preserve the integrity of the scene without destroying vital clues.
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Instructions
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Secure the scene. The first officer who arrives will usually seal off the scene from any onlookers and make sure that nothing is disturbed. Once detectives or forensic experts have arrived, they can make their examination without having to deal with any compromised evidence.
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Photograph the entire scene. Pictures can be examined at a later date, and may provide additional clues once the crime scene itself has been deserted. Start with wide pictures of the area itself, taken from the corners or walls. That provides a good overview of the crime scene. From there, move closer to take specific pictures of anything that may have bearing on the case. This includes the body, blood patterns, important objects in the room, bullet holes, broken glass on the floor, a breached safe or cabinet, shoe marks, tracked-in mud, scuff marks on the floor and anything else that seems pertinent. Thoroughness is key: The more good photos that exist, the more information the detectives will be able to refer back to.
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Take sketches of the crime scene, noting the position of any evidence and the size of the area in question. These sketches should be as accurate as possible; the distance between various points of the crime scene may be vital when considering possible clues.
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Collect any pieces of evidence that appear at the scene. This can be anything from a body on the floor to fingerprints on the window to cigarette butts in the ashtray. Each piece of evidence should be handled carefully and placed in an evidence bag for later analysis by a lab. Detectives often wear rubber gloves to prevent contamination, and extreme care must be taken not to destroy anything that may be useful. As with photographs, thoroughness is the watchword here: Anything that may be pertinent should be bagged and properly labeled. Even small things like soil samples should be included in the sweep. It's better to have something and not need it than need it and not have it.
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Take fingerprints and track marks. Fingerprints can be dusted for, and molds can be made of footprints or tire tracks in the area. You may wish to take photographs of them as well. If you do so, use a ranged camera, or provide some form of measuring gauge in the photo. That way, people will be able to tell the size of the prints just by looking at the photo.
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Remove the body. If the crime in question is a murder, the coroner will arrive and make an initial examination of the body before removing it to the lab for an autopsy. This "first pass" can provide a good impression of how the victim died, which an autopsy can later confirm or disprove.
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Take notes at all times. First impressions really do matter, and the sheer weight of information at a crime scene may conceal important clues after the first examination is over. A policeman who dutifully records everything he notices will be better set up to refer back to it as the investigation proceeds. Clear notes may also have a bearing on court cases, since the officer can refer back to them and remember the state of the crime scene months or even years after the fact.
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Tips & Warnings
Generally speaking, only trained law-enforcement officials should investigate a crime scene. Enthusiastic amateurs can cause extensive damage, and may be guilty of a crime themselves if they inadvertently destroy evidence.
