Minnesota Court Rules STRmix™ Use Is Admissible

A Minnesota court has ruled that STRmix™ – the sophisticated forensic software used to resolve mixed DNA profiles previously thought to be too complex to interpret – is generally accepted in the relevant scientific community and, therefore, is admissible in Minnesota courtrooms.

Judge Dyanna L. Street of Tenth Judicial District Court ruled that even if STRmix™ is found to be a new or novel scientific technique, its reliability and accuracy has been validated according to guidelines provided by the Scientific Working Group on DNA Analysis Methods (SWGDAM). STRmix™ has also been validated by 30 different laboratories in the U.S.

STRmix™ use initially was challenged by the defense in State of Minnesota v. Johnny Earl Edwards (File No. 02-CR-17-3290), a second degree murder case. Defense claimed that an analysis which used STRmix™ to link Edwards to the murder weapon was “novel science and does not meet the requirements of the Frye-Mack standard.”

Frye-Mack requires that a new or novel scientific technique be generally accepted in the relevant scientific community, and that the particular evidence derived from the technique and used in an individual case has a foundation that is scientifically reliable.

While the defense withdrew its motion to exclude testimony regarding STRmix™, the court – citing both its role as gatekeeper and precedent (State v. Roman Nose (649 N.W. 2d 815,818 Minn. 2002) – determined that if a scientific method is new or novel, the court has an obligation to examine whether the scientific technique is generally accepted in the scientific community before allowing evidence to be admitted at trial.

Anne Ciecko, a forensic scientist and Technical Leader at the Midwest Regional Forensic Laboratory which used STRmix™ software to analyze firearm DNA results in the Edwards case, testified that neither probabilistic genotyping nor the mathematical and biological models employed by STRmix™ are new or novel. She confirmed that probabilistic genotyping software like STRmix™ – software which performs complex mathematical computations of the statistical likelihood of individual genotypes in a DNA mixture – has been used in casework for years, while the mathematical models used in STRmix™ have been in use for centuries.

Ciecko also noted that “approximately 29 [now 30] forensic DNA profiling laboratories in the U.S. are using STRmix™ in casework, and more are currently in the process of validating the software to use in its casework.” Fifty-two U.S. labs are currently in various stages of installation, validation, and training for STRmix™.

Based on Ciecko’s testimony and the exhibits received into evidence, the court concluded “… even if the STRmix™ software is found to be novel, it is generally accepted in the relevant scientific community and is admissible in the matters [at hand].”

STRmix™ recently celebrated its fifth anniversary of use in live casework. “In five short years, STRmix™ has moved from being an experimental technology to the broadly accepted norm in cases in which a sophisticated forensic software is required to resolve mixed DNA profiles,” says John Buckleton DSc, FRSNZ, Forensic Scientist at 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), notes that STRmix™ has been successfully used “in numerous U.S. court cases and thousands of cases internationally, while there have been at least 13 successful admissibility hearings in the U.S. for STRmix™.”

ESR recently launched an upgraded version of STRmix™ after a full year of technical development and testing. STRmix™ v2.5 contains a number of new features designed to improve functionality, speed, memory, and ease of use, including: multi-kit functionality, enabling interpretation of DNA profiles from different test kits; a likelihood ratio (LR) batcher tool, allowing users to calculate multiple LRs from multiple reference inputs to a previously run deconvolution; and a combined DNA Index System (CODIS) report.

For more information about STRmix™ visit http://www.esr.cri.nz/ or http://strmix.esr.cri.nz/.

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