STRmix™ Interprets Mixed DNA Profiles Previously Considered Too Complex to Resolve
The Rhode Island Department of Health Forensic Science Laboratory is the latest U.S. forensic lab to announce plans to use STRmix™ forensic software to resolve mixed DNA profiles previously considered too complex to interpret.
STRmix™ has proven to be a highly effective tool in producing usable, interpretable, and legally admissible DNA results in a wide range of criminal cases, including violent crime and sexual assault investigations. STRmix™ has also been instrumental in helping to reexamine cold cases in which evidence originally was dismissed as inconclusive.
The Rhode Island Department of Health Forensic Science Laboratory supports the state’s criminal justice system through the accurate, thorough, and timely examination of evidence. The laboratory provides the most scientifically advanced and technologically proficient investigative capabilities available to evaluate evidence and courtroom testimony.
STRmix™ works by assessing how closely multitudes of proposed profiles resemble or can explain an observed DNA mixture. Relying on methodologies routinely used in computational biology, physics, engineering, and weather prediction, the probability of the observed DNA evidence can be calculated assuming the DNA originated from either a person of interest or an unknown donor. These two probabilities are then presented as a likelihood ratio (LR), inferring the value of the findings and level of support for one proposition over the other.
To date, STRmix™ use in interpreting complex DNA evidence has been instrumental in successfully resolving more than 300,000 cases worldwide. This success rate has led 66 local, state, federal, and private forensic laboratories throughout the U.S. – including those operated by the FBI, the Federal Bureau of Alcohol, Tobacco, Firearms, and Explosives (ATF), and the U.S. Army Criminal Investigation Laboratory (USACIL) – to begin using STRmix™.
STRmix™ is also being used in all nine state and territory forensic laboratories in Australia and New Zealand, as well as 14 labs in other countries around the globe including the U.K., Ireland Canada, Finland, Switzerland, and Denmark.
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.
Beyond these products, STRmix™ developers are planning to introduce a new version of their groundbreaking forensic software later this year. The most recent version of STRmix™ now on the market, STRmix™ Version 2.8, was introduced in the fall of 2020 and includes several new features, such as the ability to deal with more complex profiles faster and improved modelling and memory usage.
STRmix™ v2.8 also features a top-down approach that enables users to set the number of major contributors to a mixed DNA profile in which there is interest, and then obtain the LR only for those contributors.