Indiana State Police have a new tool to analyze DNA evidence.
The agency spent more than two years validating the STRmix software now being used in all cases, said Carl Sobieralski, DNA supervisor and statewide technical leader.
"We tested every kind of situation that we could possibly think of," he said, explaining the validation process. "We ran samples through the program to ensure it was making the right decisions all the time. ... There were hundreds and hundreds of samples."
The software — created in 2011 by scientists in New Zealand and Australia — recently helped secure charges against a Chesterton man in a June 2017, robbery at Zip Foods, 29 Franklin St., in Porter.
Police found latex gloves believed to be worn during the robbery near the store, but state police initially determined a mixture of DNA on the gloves could not be separated.
State police, who implemented STRmix in November, began using the software to reanalyze evidence in cases going back two years, Sobieralski said.
In the Porter robbery case, the gloves were retested, and DNA from two men was detected.
The first man had been charged shortly after the robbery, after video helped police identify him, court records state. The second man was charged in March, based in part on evidence from the state DNA lab.
Sobieralski said the new software helps analysts do what no human could.
"Mixtures of multiple people become so complex that the human brain isn't really good at figuring them out," he said. "You can't take everything into consideration. You could falsely include people, and we don't want to do that."
Previously, DNA evidence from three or more people was generally inconclusive.
"This new software allows us to interpret most three- and four-person mixtures," Sobieralski said.
Nothing about the DNA samples or how they are collected has changed.
What's different is that the software combines biological modeling, statistical theory, computer algorithms and probability distributions to infer genotypes and calculate likelihood ratios for the DNA profiles developed from forensic samples.
While running a single-source profile could take seconds, three- or four-person mixtures can take two to three hours, he said.
Indiana State Police's approximate 50 DNA analysts use multiple computers, so they can run multiple samples at one time.
In addition to re-evaluting old cases, analysts' workload has increased tremendously since a new state law that took effect Jan. 1 requiring DNA samples be taken from anyone arrested on felony charges, Sobieralski said.
During a week in March, he saw eight hits when he usually averages one or two a month, he said.
"We have to process the actual samples," he said. "Arrestees are hitting on unresolved cases."
Many of the DNA samples include people who may have been charged with felonies, but eventually pleaded guilty to misdemeanor charges and were not previously entered into the DNA database, he said. He expects to see the increase in workload taper off after the first year as the state's most prolific offenders are entered into the system, he said.
Use of software grows
Adoption of programs like STRmix is rapidly expanding worldwide. One of Sobieralski's jobs is to look for new technologies emerging in the industry, he said.
State police assembled a committee to evaluate different DNA analysis programs before choosing to purchase STRmix, he said. The committee looked at training costs, ability to implement the system, licensing fees, software support and troubleshooting, and admissibility in court, he said.
"We evaluated all of these factors to make sure we were doing what's best for Indiana," he said.
The program cost several hundred thousand dollars, which came from the laboratory budget.
Federal grant money makes up a large part of the budget, he said. Indiana State Police have received more than $20 million in the past 20 years for forensic DNA testing.
Sobieralski said state police anticipate the validity of the new software will be challenged in court. Besides training their analysts, Indiana State Police have worked to educate defense attorneys, prosecutors and crime scene investigators about the software, he said.