STRmix™ Will Interpret DNA Evidence for Mississippi Office of Forensic Laboratories

Forensic Software Produces Usable, Interpretable, Legally Admissible DNA

The Mississippi Office of Forensic Laboratories is the latest U.S. forensic lab to use STRmix™ forensic software in its scientific testing of crime scene evidence.    

Recently celebrating its 10^th anniversary, STRmix™ has established a highly successful track record of producing usable, interpretable, and legally admissible DNA evidence in a wide range of criminal cases. It has proven to be particularly effective in resolving violent crime and sexual assault cases, as well as cold cases in which evidence originally regarded as inconclusive was able to be reexamined.

Unlike traditional DNA analysis methods, STRmix™ is able to resolve mixed DNA profiles that previously would have been dismissed as too complex or degraded to interpret. It does this by assessing how closely multitudes of proposed DNA profiles resemble or can explain an observed DNA mixture, relying on proven methodologies commonly used in computational biology, physics, engineering, and weather prediction.

“The probability of the observed DNA evidence can be calculated by assuming the DNA originated from either a person of interest or an unknown donor,” explains one of the software’s developers, John Buckleton DSc, FRSNZ, Forensic Scientist at the New Zealand Institute of Environmental Science and Research (ESR). “These two probabilities can then be presented as a likelihood ratio (LR), inferring the value of the findings and level of support for one proposition over the other.”

“Investing in the Mississippi Office of Forensic Laboratories has always been important. This is a great addition for this office to test crime scene evidence,” says Commissioner Sean Tindell. “Thank you to Director Mary Dukes and her team, who have continued to go above and beyond to continue bringing in innovative technologies to advance the work being done.”

The Office of Forensic Laboratories is comprised of the Mississippi Forensics Laboratory and the Office of the State Medical Examiner. The Mississippi Forensics Laboratory provides a full range of forensic services to law enforcement agencies throughout the state, while the Office of the State Medical Examiner provides thorough investigations of all deaths affecting the public interest. Any death that occurs from a homicide, suicide, unattended, unexplained, SIDS, and accident falls under the jurisdiction of the Office.

In addition to its use by such well-known U.S. agencies as the FBI and the Federal Bureau of Alcohol, Tobacco, Firearms, and Explosives (ATF), STRmix™ is now being used in forensic laboratories in Australia, New Zealand, the U.K., Ireland, Canada, Finland, and Switzerland. To date, it has been used by these labs to interpret DNA evidence in more than 380,000 cases.

The success STRmix™ has enjoyed to date led the team behind its development to introduce two related products which in combination with STRmix™ complete the full workflow(external link) from analysis to interpretation and database matching:

• DBLR™, an application which when used with STRmix™ allows forensic laboratories to undertake superfast database searches, visualize the value of their DNA mixture evidence, and carry out mixture to mixture matches, now allowing kinship analysis; and
• FaSTR™ DNA, expert forensic software which rapidly analyzes raw DNA data generated by genetic analyzers and standard profiling kits and assigns a number of contributors (NoC) estimate.

A new version of DBLR™ – featuring improved modelling through the introduction of linkage, mutation, and F_ST to the Kinship module, and the ability to assign LRs within the Kinship module for single source profiles containing both STR and SNP loci generated using Next Generation Sequencing (NGS) technology – was introduced in December 2021.