Scene Investigation

Crime scene technicians, a medical examiner or investigator, and law enforcement detectives all take part in examining the scene for clues. The following is a list of different types of evidence that may be found at the scene, and how they are usually collected and preserved. Most of these items are usually collected by the crime scene technician.

Blood — Dried particles should be scraped into a dry container. Some dried areas may be sampled with a wet swab. The specimen should be dried before sealing it in a container. Articles of clothing or other objects containing blood may be submitted to a laboratory for a technician to remove.

Semen — The article of clothing should be collected or the specimen on the clothing can be lifted with water or saline.

Fingerprints — Soft objects containing an impression, such as clay, may be collected in their entirety. Prints on hard objects like glass or furniture should be lifted at the scene.

Firearms and other weapons — These should be submitted to a lab without special treatment at the scene. The technician must ensure proper handing so that fingerprints are not smudged or ruined. The pathologist performing the autopsy may need to see a suspected weapon for comparison with injuries on the body.

Bullets and cartridges — These should not be grasped with metal forceps because points of comparison may be damaged.

Hairs and fibers — These should be placed in separate containers and should not be crushed with a hard object such as metal tweezers.

Suspicious foods and pills — Each item should be placed in separate containers or bags to prevent contamination.

Footprints and tire marks — At the scene, casts should be made and close-up photographs should be taken.

Tool marks — There should be close-up photographs of the marks made by tools and, if possible, the damaged material should be removed for analysis by a lab technician.

Blood spatters — These should be photographed and described for analysis as to distance and angle of splatter. Samples may be removed for testing and preservation.

Other — Glass, soil, documents, cigarette butts, tobacco, and items thought to be involved in arson should all be collected and submitted to a lab.

Every scene should be diagrammed and photographed. Some jurisdictions are now using video in additions to still photography. Each item submitted to the lab should be referenced by either a photograph or written description as to its location in the scene. All containers with items submitted to the lab must be labeled with a case number, date, time, and name of the person who collected the specimen. Each specimen must have a chain of custody to determine who handled the specimen from the time it was initially packaged to the time it was stored after the analysis.

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