It worked by applying a combination of mathematical modelling and DNA interpretation methods, and could be used to compare DNA profiles against a person of interest and calculate a likelihood ratio.
According to local media reports, STRmix was used to analyse car keys, bullets, gloves and a black hooded sweatshirt later recovered from a car stolen from one of the victims and from the culvert the vehicle was left in.
Early tests showed a mix of DNA that couldn't be matched to any single suspect, before police turned to the Kiwi tech that eventually led them to Steward.
"In this case in the US, STRmix allowed the software to match mixed DNA profiles directly against a database," ESR chief executive Keith McLea said.
"This is a major advance for cases where there are no suspects and there is DNA from multiple contributors in one sample."
Before the scientific breakthrough, forensic scientists had been unable to draw conclusions from complex mixed DNA samples, McLea said.
Also in Florida this month, it was reported STRmix had allowed police in Sarasota to charge a man nearly a decade after a woman was raped and murdered inside her home.
Sarasota County Sheriff's Office spokeswoman Kaitlyn R. Perez told the Bradenton Herald how STRmix was used to test DNA taken from the clothes of Georgann Lee Smith.
The results pointed them to Delmer Smith, who had already been sentenced to death, and life in prison, over two separate cases unrelated to the killing of Georgann Lee Smith.
Along with many other US local, state and federal law enforcement agencies, STRmix was now being used by the US Army Criminal Investigation Laboratory, the Federal Bureau of Investigation, Michigan State Police, Texas Department of Public Safety, and the California Department of Justice.
The software is also used in labs here, and in Australia, England, Scotland, Ireland, Canada, Dubai, Hong Kong, Finland, Switzerland and China.
