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How Forensic Experts Collect Evidence

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When forensic experts process a crime scene, they engage in exacting procedures of documentation and the collection of any physical evidence the experts find.  Examples of evidence collected are latent fingerprints, blood, hair, human or animal bones, semen, fibers, threads, glass, paint, flammable liquids or flammable liquid residue, teeth, gunshot residue, tools, controlled substances, medicine, documents, and any other evidence the expert feels will help in catching the perpetrator of the crime.

Handling of Evidence:

The forensic expert has to be very careful when collecting evidence from a crime scene.  He may pick up remove a strand of hair from a piece of furniture.  In order to preserve the evidence, he would use a pair of tweezers to pick up the hair and drop it in a test tube or a plastic bag.  Safekeeping of the evidence is essential because contaminated evidence will obstruct the investigation.  The expert wears plastic gloves whenever he needs to touch any evidence.

Other Types of Evidence:

Each piece of evidence is tagged, logged in, and packaged to keep it intact for travel to the lab.  The forensic expert may make a plaster cast of tire tracts or footprints, remove dried blood, or small items such as a knife or hammer that was possibly used as a murder weapon.  Spent bullet casings are picked up, bagged and categorized for later analysis.

Small Items of Evidence:

Many times the evidence at a crime scene requires searching for “a needles-in-a-haystack,” such as bullet fragments or other minute items. 

When evidence is collected from carpets, sections of the carpet are vacuumed, and the dust put in separate, new bags.  Later, this dust is sifted for trace evidence.

All evidence is packaged separately in hermetically-sealed containers or in packaging dictated by the protocols of the law enforcement agency in charge of the investigation.

Strict Guidelines:

In a crime scene investigation, collection of the evidence can make the difference between catching a criminal or allowing him to go free.  It is essential that strict guidelines are followed during evidence collection to ensure that all evidence may be used to find the perpetrator and to convict him at the time of trial.


Forensic Information: How experts collect evidence.  (n.d.) essortment., Retrieved on January 15, 2011, from

Crime and Forensics. (n.d.). The Discovery Channel, Retrieved on January 15, 2011, from

Layton, J. (n.d.). How Crime Scene Investigation Works. Howstuffworks. Retrieved on January 15, 2011, from

Forensic Scientist. (2011). eHow. Retrieved on January 15, 2011, from

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