October 9, 2018 10:35:00 AM
In 2010, forensic DNA analyst Kathryn Rodgers created a DNA profile of the suspect in a 30-year-old sexual assault.
"At the time, I believe they didn't even have to have a full sexual assault kit formed -- I don't know if they even did them -- but they did have at least one swab taken from the victim's body," said Rodgers, who has worked for 10 years at Scales Laboratory in Brandon. "... We tried DNA testing on it and specifically Y chromosome analysis, which is specific for Y chromosomes DNA which is handy in a lot of sexual assault cases with female victims. And we did get a pretty good Y chromosome profile."
It's far from the only cold case Rodgers and other forensic scientists have contributed to solving by creating DNA profiles out of evidence collected before DNA analysis was something law enforcement even knew to use in criminal investigations. As DNA technology and science advances, more law enforcement agencies are turning to that branch of science to find new leads in cold cases.
Two such cold cases in the Golden Triangle area have resulted in arrests in the last two years. In May 2017, Columbus Police Department arrested a suspect in the 1996 murder of 71-year-old Columbus resident Mack Fowler. On Monday, Starkville Police Department announced the arrest of 51-year-old Michael Devaughn for the 1990 Labor Day murders of Starkville residents Betty Jones, 65, and Kathryn Crigler, 81.
In both cases, law enforcement had collected DNA from crime scenes before the departments had a policy of finding labs to create DNA profiles.
It's evidence that leaves "no wiggle room," said SPD Sgt. Bill Lott, lead investigator for the Labor Day murders.
"You know you've got a good instrument of evidence when you have something like that," he said. "It doesn't discriminate and there's no bias. The science is the science. That's why, to me, I love the science issue. It is what it is."
During the Labor Day murders investigation, Lott worked with both Scales in Brandon and Reston, Virginia-based Parabon NanoLabs -- both private labs which analyze DNA evidence collected from crime scenes to provide law enforcement with leads in violent crimes like murder and sexual assault. Lott did not indicate how each lab helped in the case or making the arrest, citing the ongoing investigation.
Scales receives evidence from law enforcement around the state -- sometimes cold cases and sometimes not.
"We're typically tasked with looking for potential sources of DNA on items of crime scene evidence, whether it be just through contact -- you know, DNA is shed through our skin cells so just by having contact or handling an item, there's potential for leaving skin cells behind -- or through body fluids -- blood, semen, saliva," Rodgers said.
With luck, she said, they can create a single-source profile, meaning a complete DNA profile of one individual that can be compared to a suspect or victim in a crime.
"If an exact match for that is found, then we're talking about frequencies of less than 1-in-999 trillion of finding that profile again in the general world population, with the exception of identical twins," Rodgers said. "In those situations when we're dealing with an exact match, single-source profile, that frequency is so low that most of the time, that person's profile is considered to be unique to them and so a match like that would be considered conclusive."
Investigators can also compare those profiles to the Federal Bureau of Investigation's Combined DNA Index System (CODIS), a national database of DNA profiles from people who have been arrested or convicted of crimes.
Other sources for DNA matching
The catch with that is that if a perpetrator hasn't been arrested for anything, then his or her match won't be in the database -- which is where Parabon comes in," said Ellen Greytak, director of bioinformatics and the Snapshot division at Parabon.
"Traditional forensic DNA analysis is just for matching DNA from a crime scene to an individual, so either a suspect you've already identified or to a database," Greytak said. "And it's great for that, but if you don't get a hit in either of those places, it can't really tell you anything else. What we're trying to do is generate new information, new leads out of that DNA."
Using evidence from crime scenes, Parabon scientists can utilize DNA phenotyping.
"We predict an individual's physical traits -- their eye color, their hair color, their ancestry, their face shape ... from the DNA and that can help the investigators figure out who they should and shouldn't be looking for," she said. "We're not producing a photograph of the individual, but we're producing a description of them."
They also utilize Genetic Genealogy, which means they run the DNA against public database GEDmatch, a database similar to Ancestry.com, in which people have willingly submitted their DNA knowing law enforcement can use it to identify remains or narrow down suspect lists in violent crimes.
It's a new branch of science that Parabon only began offering law enforcement this year, Greytak said. So far, there are no laws regulating it, though Parabon only runs DNA profiles against public databases where they know the individuals who submitted DNA have already agreed law enforcement can use it to compare in investigations.
Parabon also specializes in cold cases, Greytak said. It's rare for them to have a case from the last 10 years. The oldest case they have right now is 51 years old.
Both Greytak and Rodgers emphasized that the age of the DNA matters less than the size of the DNA sample and how it was stored.
"If the DNA is there to begin with and it's of a decent-enough quality, meaning it has not been degraded, well then there's no reason to not get it as long as that sample's in good enough condition as long as it's not going to damage or degrade," Rodgers said.
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