U.S. flag

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

STR Data Analysis and Interpretation for Forensic Analysts

Negative Control(s) & Reagent Blanks

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

Negative Control(s) & Reagent Blanks
National Institute of Justice (NIJ) (see reuse policy).

Reagent blanks are routinely processed with samples. Laboratories include reagent blanks in the extraction, quantitation, and amplification processes to aid in monitoring potential contamination of reagents and/or supplies. These blank samples should show no DNA pattern other than that of the internal size standard. Negative controls or reagent blanks showing unexplained extraneous DNA could indicate contamination.

Analysts should closely evaluate blank samples, including assessment of peaks under the established threshold. If there is a discernable pattern of allelic activity that cannot be attributed to a spike, pull-up, or other artifact, the analyst should troubleshoot the problem and follow the procedures established by the laboratory.

Read more about detecting and preventing contamination in course: DNA Amplification.

(You may have to enter your Userid and password.)

Back Forward