Success Story: Addressing a Key Challenge for PCR-Based Forensic Tests

Success Story: Addressing a Key Challenge for PCR-Based Forensic Tests

National Institute of Justice and DNA Polymerase Technologies


April 2016


Polymerase Chain Reaction (PCR) inhibitors are present in blood, soil, and reagents, and represent a key challenge for PCR-based forensic tests, resulting in false negatives and poor sensitivity of results. Partial Short Tandem Repeat (STR) profiles obtained in the presence of PCR inhibitors appear similar to degraded DNA profiles, which is a major concern for downstream analysis and reporting results obtained from forensic samples. Thermofisher’s AmpliTaq Gold®, a DNA polymerase enzyme that is widely used in forensic DNA testing, is sensitive to PCR inhibitors and can completely inhibit a PCR reaction in the presence of less than 0.1% whole blood. Therefore, current DNA typing protocols must be adapted to achieve a high degree of purity of the evidentiary sample. In general, DNA extraction procedures can be time-consuming or labor-intensive, can cause DNA loss, and may fail to completely remove common inhibitors. Additionally, multiple sample manipulations may increase the risk of cross-contamination. This NIJ funded research examined the effects of PCR inhibitors on the DNA polymerase enzyme from alternative Thermus aquaticus (Taq) mutants and explored an approach to eliminate the need to extract and purify DNA prior to PCR. Removing this step decreases the required time, lowers the cost, and increases the efficiency of forensic DNA typing.

“DNA Polymerase Technologies has done impressive work engineering Taq mutants and in determining the proper combination of PCR enhancer cocktails to assess STR profiles in challenging samples."

- Robert Bever, Ph.D. | Laboratory Director Mitotyping Technologies,
A Division of American International Biotechnology

Funding for this Forensic Technology Center of Excellence success story was provided by the National Institute of Justice, Office of Justice Programs, U.S. Department of Justice.

The opinions, findings, and conclusions or recommendations expressed in this success story are those of the author(s) and do not necessarily reflect those of the U.S. Department of Justice.

Contact us at with any questions and subscribe to our newsletter for notifications.

Related Content

test tubes and scientists

Things Are Not What They Seem: A Collection of Interesting Case Studies from the Medical Examiner Scene Queens

← Back to Unseen Threats Webinar Series This webinar originally occurred on Thursday, May 19, 2022 Duration: 1 hour Overview With the rise of illicit fentanyl, fentanyl analogues, synthetic cathinones, xylazine, and other substances adulterating many traditional street drugs, users often…
pills and IV

Unseen Threats: A Webinar Series from the AAFS Opioids and Emerging Drugs Ad-Hoc Committee

Overview This webinar series is based on the one-day workshop (“Unseen Threats”) that was sponsored by the Opioids and Emerging Drugs Ad-Hoc Committee at the 2022 American Academy of Forensic Sciences (AAFS) Annual Meeting. To follow up on this workshop,…
woman sad

Strangulation in Sexual Assault Cases: Considerations for Evidence Collection and Supporting Healing

← Back to 2022 Sexual Assault Awareness Month Webinar Series This webinar originally occurred on April 14, 2022 Duration: 1 hour Overview In addition to providing medical care and support to victims of sexual assault, Sexual Assault Nurse Examiners (SANEs)…