What Are the Different Techniques for Evidence Preservation?

A law enforcement officer's ability to solve a crime may depend on proper evidence preservation at the scene of the crime. Most crime scenes leave a plethora of evidence that must be meticulously collected and then preserved in order to provide investigators with clues used to solve the crime. Proper evidence preservation starts with securing the scene of the crime and making notations about how the scene appeared when the first responders arrived. Next, each piece of evidence must be carefully collected and placed in the appropriate container depending on what type of evidence it is. Once collected, the evidence must be preserved or stored correctly in order to be able to use it at trial or test it for clues.

When first responders arrive at the scene of a crime, the most important stage of evidence preservation begins. First responders must be certain not to disturb the scene and must secure the area immediately. The proper personnel should be contacted, such as the coroner, detectives, or crime scene investigators, and detailed notes should be taken regarding the condition of the scene upon arrival.

Once the proper personnel arrive, each potential piece of evidence must be properly collected. Fragile evidence, or evidence that may be easily destroyed or mutilated, should be collected first. Techniques involved in evidence preservation include collecting the evidence with the appropriate tools and then preserving the evidence in the appropriate type of container.

Understanding how to collect the evidence is crucial. For example, hair evidence should be collected with tweezers and placed in a seal-tight plastic bag. Fingerprints are usually gathered by dusting and then lifting the print and placing it on a slide. Blood evidence is generally gathered with the appropriate cotton swab or gauze and then air-dried and properly refrigerated.

Once the evidence has been collected, evidence preservation requires that it be properly preserved for a number of reasons, including use at trial, study, and return to the owner, in some cases. In most jurisdictions, the original evidence collected at a crime scene must be presented at a trial, which requires proper preservation of the evidence. In addition, many types of evidence, such as hair, fingerprints, or blood evidence, may be used by forensic scientists to gather additional clues, such as a DNA profile or fingerprints of a potential suspect. In some cases, the evidence must be returned to the proper owner if it is not used at trial, or if it turns out to be irrelevant to the case.