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Principles of Forensic DNA for Officers of the Court

Special Interpretation Considerations Related to Sexual Assault Cases: Differential Extraction (cont.)

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Photo of gloved hands taking test tubes out of a machine
National Institute of Justice (NIJ) (see reuse policy).

Labs may report these two fractions as:

  • Male fraction and female fraction (though in a male on male assault, these terms may be misleading).
  • Sperm fraction and non-sperm fraction.
  • S (sperm) fraction and E (epithelial) fraction.
  • Fraction 1 and fraction 2.

Complete separation may not be possible for a variety of reasons. In such cases, one or both fractions may contain a mixture of sperm and non- sperm DNA. This does not necessarily preclude interpretation of results.

Note: the remainder of the module will use the terminology sperm and non-sperm fractions.

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