WASHINGTON, DC – STRmix™ – sophisticated forensic software capable of resolving mixed DNA profiles previously thought to be too complex to interpret – has been used to convict a Wyoming man of third-degree sexual assault, a felony punishable by imprisonment for up to 15 years.
Wyoming’s State Crime Laboratory used STRmix™ to test for DNA on the couch cushions on which the sexual assault was alleged to have taken place.
Jennifer Brammeier, Senior Forensic Scientist with the State Crime Lab, testified that DNA from both the victim and the defendant – Casper, Wyoming businessman Tony Cercy – was present on the cushion cover. She noted that the DNA on the cushion was 52.6 sextillion times more likely if it was from both individuals than if it was random.
Brammeier’s testimony was bolstered by testimony from John Buckleton, DSc, FRSNZ, one of the developers of STRmix™.
Pointing out that STRmix™ is now routinely used to resolve DNA profiles by 38 U.S. forensic labs, including the FBI and the Bureau of Alcohol, Tobacco, Firearms, and Explosives (ATF), Dr. Buckleton explained that STRmix™ builds up a picture of the DNA genotypes present that, when added together, best explains the observed mixed DNA profile. STRmix™ then enables analysts to compare the results against a person or persons of interest and calculate a statistic, or “likelihood ratio,” of the strength of the match.
According to Dr. Buckleton, the likelihood ratio has largely replaced talk about whether a DNA sample found at a crime scene is a “match” with someone’s known DNA as new methods of DNA analysis such as STRmix™ have become widely used in forensic labs worldwide.
Cercy initially was charged with one count each of first-degree assault (rape), second-degree assault (intrusion), and third-degree assault (sexual contact).
In February 2018, a Natrona County jury acquitted Cercy of the first- and second-degree counts, but deadlocked on the third-degree count. After a mistrial was declared, attorneys for the alleged victim asked for the case to be retried. The request for retrial was granted, but the trial was moved to Thermopolis after the defense cited concerns over intense publicity before, during, and after the trial.
STRmix™ has now been used successfully in a number of U.S. court cases, as well as thousands of cases internationally. There have also been at least 24 successful admissibility hearings in the U.S. for STRmix™.
A new version of STRmix™, STRmix™ v2.6, was introduced in August 2018. The new version features a user interface that has been completely redeveloped and refreshed, providing users with vastly improved usability and workflow. Version 2.6 also enables a range of contributors to be entered when performing a deconvolution, and any type of stutter to be added and configured.
Jo-Anne Bright of the New Zealand Institute of Environmental Science and Research (ESR) and Duncan Taylor from Forensic Science South Australia (FSSA) worked together with Dr. Buckleton on the development of STRmix™.
For more information about STRmix™ visit www.strmix.com.
