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Contaminated evidence
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Contaminated evidence
Contaminated evidence is any foreign material that is introduced to a crime scene after the crime is committed. Contaminated evidence can be brought in by witnesses, suspects, victims, emergency responders, fire fighters, police officers and investigators.
Juries expect to see forensic evidence before they render a verdict based on that evidence. Because of this, attorneys on both sides try to discredit forensic evidence that does not support their clients' interests. This requires crime scene investigators be especially careful to guard against contamination in the forensic samples. A miscarriage of justice can occur when these procedures are not carried out carefully and accurately.
Evaluating a scene before anyone enters can be key to keeping contamination to a minimum. The examination of the scene will usually begin with a walk-through of the area along the "trail" of the crime. The trail is that area in which all apparent actions associated with the crime took place. The trail is usually marked by the presence of physical evidence. This may include the point of entry, the location of the crime, areas where a suspect may have cleaned up, and the point of exit. In some cases, a walk-through may become secondary if potential evidence is in danger of being destroyed. In that case, this evidence should be preserved or documented, and collected as quickly as possible.
The most important aspect of evidence collection and preservation is protecting the crime scene. This is to keep the pertinent evidence uncontaminated until it can be recorded and collected. Eating, drinking, or smoking should never be allowed at a crime scene. A command post should be set up for such purposes. The post is to be set up somewhere outside the restricted areas. It could be a vehicle, picnic table, hotel room, tent, etc. It can be used as a gathering place for non-involved personnel, a place for investigators to take breaks, eat, drink, or smoke, a communication center, a place for press conferences, a central intelligence area, etc.
Protection of the crime scene also includes the protection of the crime scene investigators. Whether a civilian or a police crime scene investigator, one person should never be left alone while processing the scene. This is especially true if the suspect has not been apprehended. There are many stories of suspects still hiding at or near their area of misdeed. That is why there should always be at least two people working the scene. At least one of these people should have a radio and a firearm.
The taping should begin with a general overview of the scene and the surrounding area. The taping should continue throughout the crime scene using wide-angle, close up, and even macro (extreme close up) shots to demonstrate the layout of the evidence and its relevance to the crime scene.
The final phase in documenting the scene is making a crime scene sketch. The drawback of photographs is that they are two-dimensional representations of three-dimensional objects. As a result, most photographs can distort the spatial relationships of the photographed objects causing items to appear closer together or farther apart than they actually are. If spatial relationships of the evidence are important or if something needs to have proportional measurements included in it for calculations (such as bullet trajectory angles, accident reconstructions, etc.), then a sketch must be made of the crime scene.
Once the crime scene has been thoroughly documented and the locations of the evidence noted, then the collection process can begin. Most items of evidence will be collected in paper containers such as packets, envelopes, and bags. Liquid items can be transported in non-breakable, leakproof containers. Arson evidence is usually collected in air-tight, clean metal cans. Only large quantities of dry powder should be collected and stored in plastic bags. Moist or wet evidence (blood, plants, etc.) from a crime scene can be collected in plastic containers at the scene and transported back to an evidence receiving area if the storage time in plastic is two hours or less, and this is done to prevent contamination of other evidence.
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Contaminated evidence AI simulator
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Contaminated evidence
Contaminated evidence is any foreign material that is introduced to a crime scene after the crime is committed. Contaminated evidence can be brought in by witnesses, suspects, victims, emergency responders, fire fighters, police officers and investigators.
Juries expect to see forensic evidence before they render a verdict based on that evidence. Because of this, attorneys on both sides try to discredit forensic evidence that does not support their clients' interests. This requires crime scene investigators be especially careful to guard against contamination in the forensic samples. A miscarriage of justice can occur when these procedures are not carried out carefully and accurately.
Evaluating a scene before anyone enters can be key to keeping contamination to a minimum. The examination of the scene will usually begin with a walk-through of the area along the "trail" of the crime. The trail is that area in which all apparent actions associated with the crime took place. The trail is usually marked by the presence of physical evidence. This may include the point of entry, the location of the crime, areas where a suspect may have cleaned up, and the point of exit. In some cases, a walk-through may become secondary if potential evidence is in danger of being destroyed. In that case, this evidence should be preserved or documented, and collected as quickly as possible.
The most important aspect of evidence collection and preservation is protecting the crime scene. This is to keep the pertinent evidence uncontaminated until it can be recorded and collected. Eating, drinking, or smoking should never be allowed at a crime scene. A command post should be set up for such purposes. The post is to be set up somewhere outside the restricted areas. It could be a vehicle, picnic table, hotel room, tent, etc. It can be used as a gathering place for non-involved personnel, a place for investigators to take breaks, eat, drink, or smoke, a communication center, a place for press conferences, a central intelligence area, etc.
Protection of the crime scene also includes the protection of the crime scene investigators. Whether a civilian or a police crime scene investigator, one person should never be left alone while processing the scene. This is especially true if the suspect has not been apprehended. There are many stories of suspects still hiding at or near their area of misdeed. That is why there should always be at least two people working the scene. At least one of these people should have a radio and a firearm.
The taping should begin with a general overview of the scene and the surrounding area. The taping should continue throughout the crime scene using wide-angle, close up, and even macro (extreme close up) shots to demonstrate the layout of the evidence and its relevance to the crime scene.
The final phase in documenting the scene is making a crime scene sketch. The drawback of photographs is that they are two-dimensional representations of three-dimensional objects. As a result, most photographs can distort the spatial relationships of the photographed objects causing items to appear closer together or farther apart than they actually are. If spatial relationships of the evidence are important or if something needs to have proportional measurements included in it for calculations (such as bullet trajectory angles, accident reconstructions, etc.), then a sketch must be made of the crime scene.
Once the crime scene has been thoroughly documented and the locations of the evidence noted, then the collection process can begin. Most items of evidence will be collected in paper containers such as packets, envelopes, and bags. Liquid items can be transported in non-breakable, leakproof containers. Arson evidence is usually collected in air-tight, clean metal cans. Only large quantities of dry powder should be collected and stored in plastic bags. Moist or wet evidence (blood, plants, etc.) from a crime scene can be collected in plastic containers at the scene and transported back to an evidence receiving area if the storage time in plastic is two hours or less, and this is done to prevent contamination of other evidence.