STRmix Test Results Ruled Admissible in Illinois Murder Case

The judge in an Urbana, IL kidnapping and murder trial has ruled that DNA test results produced by STRmix™ are admissible in the case.

In denying a motion by attorneys for the defendant, Brendt Christensen, to delay the trial until October, U.S. District Court Judge James Shadid ruled that it would be unfairly prejudicial to the prosecution not to let an FBI expert witness, Jerrilyn Conway, testify about the science behind STRmix™ and the DNA testing. (U.S. v. Brendt A. Christensen, 2:17-cr-20037)

The FBI has been using STRmix™ – sophisticated forensic software used to resolve mixed DNA profiles previously thought to be too complex to interpret – since 2015.

STRmix™ was used in the Christensen case to measure the likelihood that blood found in various locations at the scene of the crime was that of the victim, University of Illinois visiting scholar Yingying Zhang.

STRmix™ uses standard, well-established statistical methods to build up a picture of the DNA genotypes that, when added together, best explains an observed mixed DNA profile. STRmix™ then enables users to compare the results against a person or persons of interest and calculate a statistic, or “likelihood ratio,” of the strength of the match.

“STRmix™ software has greatly improved the usability of DNA. Agencies, for example, are reporting an uptick of interpretable DNA in gun cases from approximately 40% to more than 70%," explains John Buckleton DSc, FRSNZ, Forensic Scientist at the New Zealand Institute of Environmental Science and Research (ESR). “As a result, evidence is available in a much higher fraction of criminal cases than in the past.”

Dr. Buckleton, who developed STRmix™ in collaboration with ESR’s Jo-Anne Bright and Duncan Taylor from Forensic Science South Australia (FSSA), adds, “We need to help labs, prosecutors, and defenders to achieve just outcomes and avoid labs making extreme efforts to clear cases, but obtaining uninterpretable results.”

To date, STRmix™ has been used successfully in numerous U.S. court cases, including 28 successful admissibility hearings. It is currently being used by 43 federal, state, and local agencies in the U.S., and is in various stages of installation, validation, and training in more than 60 other U.S. labs.

Internationally, STRmix™ has been used to interpret DNA evidence in more than 100,000 cases since 2012. It is currently being used in all nine state and territory labs in Australia and New Zealand, as well as 11 forensic labs in England, Scotland, Ireland, Finland, Dubai, and Canada. The code for three versions of the software has now been independently examined and in all cases admitted.

STRmix™ Ltd. introduced a new version of the software, STRmix™ v2.6, 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.

For more information about STRmix™ visit

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