Since all cells throughout the body of an individual possess the same genetic information, any type of fluid and tissue extracted from the body of that particular will provide an identical DNA pattern.

The preferred specimen types for any DNA test are blood and/or buccal swabs. This is due to the fact that both sample types can easily be collected directly with the consent of the patient. Although blood sampling was traditionally believed to be the "more accurate" method, buccal swab collections have gained acceptance and is now the typically preferred method, as it has been found to be non-invasive and is easier for transport and storage. At each specimen collection appointment, four buccal swabs (similar to cotton tips) are brushed with moderate strength along the patient's inner cheek. In doing so, loosely fixed cells which have gathered at this area will adhere to the swabs for subsequent extraction of DNA at the laboratory.