STRmix, forensic software developed jointly by New Zealand’s Institute of Environmental Science and Research (ESR) and Forensic Science South Australia (FSSA) that is claimed to be able to resolve previously unresolvable mixed DNA profiles, has been credited with bringing criminals to justice in two recent US murder investigations.
According to the STRmix web site, STRmix is “a breakthrough for forensic analysts as it can assist investigations using DNA evidence that was previously considered too complex to interpret.”
It claims STRmix represents a major advance for cases where there are no suspects and there is DNA from multiple contributors in one sample because it includes a function that allows the software to match mixed DNA profiles directly against a database. On 2 February the Palm Beach Post reported that police in the small town of Jupiter had been struggling for months to find the people responsible for a triple murder.
“Three people in their 20s had been fatally shot in the backyard of a home in a town where homicides are rare,” the paper said. “But eventually, technology that fewer than 100 forensic labs nationwide are trained to use helped uncover some of the answers, authorities say.”
The paper went on to say two men had been arrested and charged eight months apart. “The second of those arrests – which came nearly 10 months after the slayings – was made possible in part by STRmix, a software program that the Palm Beach County Sheriff’s Office Forensic Biology Unit began using in August,” it said
The paper explained: “STRmix uses an algorithm to help scientists identify individual DNA contributors in evidence that contains several people’s DNA. That program helped decipher key pieces of evidence that led to the November  arrest.”
Just days later, on 6 February the Bradenton Herald — a local paper for another town in Florida — reported that STRmix had “enabled the Sarasota County Sheriff's Office to charge Delmer Smith nearly nine years after a 37-year-old woman was raped and killed inside her home.”
The report said that Smith — who is already serving a life sentence for other home invasions and kidnapping — had been charged with the new crime after his DNA had been submitted to DNA Labs International, which had only recently acquired the STRmix technology.