STRmix™ Is Generally Accepted, Scientifically Valid, Arizona Court Rules

Arizona Superior Court for Pima County has denied the defendant’s motion to preclude DNA evidence in the trial for the murder of Robert Belman.

Defense counsel in Arizona v. Martinez (Case No. CR-20181689-001) had challenged the relevancy, admissibility, and reliability of DNA results obtained by the State largely through the use of STRmix™ – sophisticated probabilistic genotyping software used to resolve mixed DNA profiles previously thought to be too complex to interpret.

The court, however, concluded, “…the use of probabilistic genotyping, and specifically the software utilized in this case – STRmix™ – has been generally accepted in the relevant scientific community of forensic DNA.”

The court’s ruling continued, “… even the defense’s motion concedes that most state and federal courts have found that STRmix™ is scientifically valid because of it having been subjected to several peer reviewed studies that produces favorable results.”

John Buckleton, DSc, FRSNZ, one of the developers of STRmix™, notes that forensic labs worldwide increasingly are using STRmix™ “because it greatly improves the usability of DNA to produce evidence in a wide range of criminal cases.”

Buckleton notes that organizations using STRmix™ are reporting a significantly higher rate of interpretable results in sexual assault cases, as well as “an increase of interpretable DNA in gun cases from about 40% to more than 70%.”

Since its introduction in 2012, STRmix™ has been used successfully in numerous U.S. court cases, including 37 successful admissibility hearings. Currently, 56 U.S. forensic labs, including multiple state and local organizations and such federal agencies as the FBI and ATF, use STRmix™ to interpret DNA profiles. The software is also in various stages of installation, validation, and training in more than 60 other U.S. organizations.

Internationally, STRmix™ has also gained widespread acceptance. All nine state and territory forensic labs in Australia and New Zealand, as well as 14 labs in other countries including England, Scotland, Ireland, Finland, Denmark, and Canada, now use STRmix™. To date, it has been used to interpret DNA evidence in more than 120,000 cases worldwide.

A new version of STRmix™, STRmix™ v2.7, was introduced in late 2019. STRmix™ v2.7 includes several new features in response to improvements recommended by forensic labs to better address the on-the-job needs they regularly encounter.

The team that created STRmix™ recently launched two other products. DBLR™, an application used with STRmix™, allows users to undertake superfast database searches, visualize the value of their DNA mixture evidence, and carry out mixture to mixture matches. FaSTR™ DNA, meanwhile, is expert forensic software that rapidly analyzes DNA profiles and assigns a Number of Contributors (NoC) estimate.

Designed by scientists for scientists, FaSTR™ DNA combines an intuitive, user-friendly graphical interface with easily understandable and laboratory-customizable rules to expedite the analysis of raw data generated by genetic analyzers and standard profiling kits. FaSTR™ DNA also implements the use of artificial neural networks for peak classification independent of and in parallel to the forensic analyst.

Alongside STRmix™, FaSTR™ DNA and DBLR™ complete the full workflow from analysis to interpretation and database matching.