U.S. flag

An official website of the United States government, Department of Justice.

Forensic DNA Education for Law Enforcement Decisionmakers

DNA Analysis, Extraction

Home  |  Glossary  |  Resources  |  Help  |  Contact Us  |  Course Map

Time Required to Perform Laboratory Analysis

Step 3: DNA Analysis, Extraction

illustration of test tubes
National Institute of Justice (NIJ) (see reuse policy).

Extraction is the process of removing DNA from a stain and, if necessary, removing residual stain material from the DNA. If the stain is identified as semen, additional extraction steps are required to separate sperm cells from the other cells in the stain. Sperm separation doubles the time required for the extraction process and creates two independent subsamples that are carried through all subsequent processes. The first subsample is predominantly composed of sperm DNA, while the second subsample is from other cells. In a sexual assault case, this technique allows the separation of DNA from the male and female components. In most casework analyses, it is important to determine the amount of sperm and non-sperm DNA present in the extract.

Back Forward