There are many challenges when it comes to interpreting DNA evidence, particularly if it’s low-quality, in very small amounts or comes from a mixture of DNA from several individuals.  

PHF Science, in partnership with Forensic Science South Australia, set out to address these challenges in 2009. They began to investigate a newer method called probabilistic genotyping, which uses mathematical models to analyse more of the information in a DNA profile. Together, they created STRmix™, a software program that uses biological modelling and standard mathematical processes to interpret complex mixed DNA profiles, outperforming older and more manual methods.

Beyond direct comparison of crime scene samples with persons of interest, the software can also be used to match mixed DNA profiles directly against the DNA Profile Databank. This is a breakthrough for cases where there are no persons of interest and there is DNA from multiple unknown individuals in one sample. STRmix™ builds millions of conceptual DNA profiles, finding the combinations that best explain the evidential profile.  

STRmix™ has been adopted worldwide and used in more than 700,000 cases to date. The software has become a leading forensic science tool in Australasia, the USA, UK and elsewhere. In recognition of its impact, the STRmix team was awarded the Prime Minister's Science Prize in 2018. The STRmix team is dedicated to supporting the software, in addition to a further four software applications that they have subsequently developed.