President's DNA Initiative
Advancing Justice Through DNA Technology
DNA Analyst Training
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Home > Forensic Biology > Testing of Body Fluids & Tissues > Overview
collage of hair, skin, sperm, and blood cells

Serology is the detection, identification, and typing of body tissues, either in native form or as stains or residues left at a crime scene. Most often, the tissue of interest is a body fluid such as blood or semen; however other tissues such as hair or bone are encountered. The detection and identification process begins with a physical examination, followed by a screening test, and may include confirmatory identification and sample typing. Typing is the detection of genetically determined characters in the sample. A difference in type between the stain and reference sample from the postulated source may provide a positive elimination. If there is no elimination, the results can be evaluated against population frequency data to give a measure of the significance of the failure to eliminate.

The features of a good typing system are that it


It is not required that a typing system be based on an inherited characteristic, although in practice they all are.

The very presence of biological fluids, specifically blood and semen, may be an indication of a serious crime and of evidential value. The physical distribution of blood stains at the scene or on clothing may produce valuable information about the crime.

Characterization of biological fluids is often used to associate forensic evidence with an individual. Testing allows conclusions to be drawn as to the person from whom the fluid originated. 

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© 2007 NFSTC Science Serving Justice®
NOTE TO USERS: The President’s DNA Initiative DNA Analyst Training program and assessment were completed and published in 2005, in cooperation with the National Institute of Justice. The science and techniques in the program are sound and proven, however, program content has not been updated to include tools and technologies developed and in use after 2005, including many kits and robots. Assessment questions address only content delivered in this program and may not contain the full range of tools in use in your laboratory.