Criminal cases in Texas and Michigan have reaffirmed the use and reliability of STRmix™ – a sophisticated forensic software used to resolve mixed DNA profiles previously thought to be unresolvable.


In the first case, the Texas Court of Appeals for the 12th District recently ruled that a preponderance of evidence, including a DNA analysis which was conducted using STRmix™, was legally sufficient to affirm a lower court conviction for aggravated assault.


Meanwhile, Michigan’s Berrien County Trial Court rejected a defense challenge to the admissibility and use of STRmix™, affirming that the software met the Daubert Standard regarding the admissibility of expert witness testimony.


“Coming on the heels of a recent Florida case affirming the use of STRmix™ and the FBI’s validation of STRmix™ for use on mixtures of up to five persons, these cases offer continued proof that STRmix™ is sufficiently robust for implementation in forensic laboratories,” says John Buckleton of the New Zealand Institute of Environmental Science and Research (ESR).


Buckleton, who developed STRmix™ in collaboration with ESR’s Jo-Anne Bright and Duncan Taylor from Forensic Science South Australia (FSSA), continues, “STRmix™ provides numerous advantages over historical methods of DNA profile analysis and greater statistical power for estimating evidentiary weight, all of which can be used reliably in human identification testing.”


In the Texas case, Roy Edward Smith v. State of Texas, forensic scientists used STRmix™ to associate the appellant’s DNA with a sock tied to a piece of concrete used to assault the victim, Victoria Massey. The Texas Court of Appeals concluded that the evidence in the case – which included the DNA left on the sock, one of the weapons used to assault Massey; the appellant’s proximity to and familiarity with the area of the attack; his conflicting stories about the attack; and his resemblance to a composite sketch of the attacker – was legally sufficient to support the lower court conviction.


The Michigan case, State of Michigan v. Larry David Smith, revolved around the application of STRmix™ to the analysis of DNA recovered from a Powerade bottle located near the scene of a burglary and safe breaking at a Dollar General store in Coloma, Michigan. The court ruled that STRmix™ met all Daubert considerations – i.e., it has been subjected to rigorous testing and validated; it has been subject to peer review; and it has been generally accepted in the scientific community, as well as in federal and state courts throughout the U.S.


Twenty U.S. labs are now using STRmix™, while another 70 U.S. labs are at various stages of installation, validation, and training. STRmix™ is being used by numerous local, state, and federal agencies, including the U.S. Army Criminal InvestSTRmix™ has been used in casework since 2012, and has been used to interpret DNA evidence in thousands of cases. It is currently in use in labs in Australia, New Zealand, England, Scotland, Ireland, and Canada.


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