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Crime Scene and DNA Basics for Forensic Analysts


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An outdoor crime scene is the most vulnerable to loss, contamination, and deleterious change of physical evidence in a relatively short period of time. Individuals with access to the scene can potentially alter, destroy or contaminate evidence. The risk is greatest when investigators fail to secure the crime scene properly.

Destruction or deterioration of evidence due to environmental conditions such as heat, cold, rain, snow and wind are problems associated with outdoor scenes. Evidence that cannot be protected under these conditions should be collected expeditiously without compromising its integrity. Investigators who encounter a combination of an indoor and outdoor scene should give priority to processing the outdoor component.

Nighttime outdoor crime scenes are especially problematic. Regardless of the quality of the light source used to illuminate the scenes, the lack of sunlight can lead to investigators inadvertently missing or destroying evidence. Whenever possible, outdoor crime scenes should be held and secured until daylight for processing.

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