Colorado Court Rules Evidence Produced by STRmix™ Is Relevant and Reliable

Rejecting a defense motion to exclude expert testimony regarding DNA evidence, the District Court for Weld County, Colorado has ruled that evidence produced by STRmix™ is relevant, reliable, and therefore admissible in court proceedings.

STRmix™ is sophisticated forensic software used to resolve mixed DNA profiles previously thought to be too complex to interpret. STRmix™ was used by the Colorado Bureau of Investigation to develop a DNA profile matching the defendant in the case in question, Colorado v. Billy Hendrix (Case No. 18CR1767, 18CR1921).

In denying a defense request for a Shreck hearing – which would require the trial court to serve as a gatekeeper in determining whether expert testimony is reliable and relevant, and thereby admissible – the District Court order notes, “The prosecution has provided support that courts applying reliability tests have repeatedly admitted STRmix™ testimony and results.”

The order goes on to state, “Considering factors similar to those outlined in Shreck, courts in at least Colorado, Illinois, Wyoming, New York, New Mexico, Minnesota, Michigan, Connecticut, Florida, California, and the Virgin Islands have found probabilistic genotyping and STRmix™ sufficiently reliable to be admitted and submitted to the jury.”

Since its introduction in 2012, STRmix™ has been used to interpret DNA evidence in more than 120,000 cases around the world. It has also been used successfully in numerous U.S. court cases, including at least 35 successful admissibility hearings.

STRmix™, which has been used by the FBI laboratory since 2015, “is based on well-established mathematical principles, has been thoroughly vetted by the scientific community, and has been found to perform reliably in studies and casework,” according to the court order.

It has also been “subjected to thorough validation studies by those responsible for developing the software and has been internally validated by at least 46 [actually now 56] forensic laboratories in the United States … Furthermore, STRmix™ has been peer reviewed. Over 50 peer-reviewed papers have been published in scholarly journals supporting STRmix’s™ validity,” the order concludes.

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

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

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.