DNA evidence crucial in two recently solved Sarasota cold cases

Deputies, police solve murders of Deborah Dalzell, Judith Doherty

DNA evidence crucial in two recently solved Sarasota cold cases

SARASOTA (WWSB) - On September 19th, 2018 came the news that Deborah Dalzell’s family has waited decades to hear.

“Today, more than 19 years after her death, the man responsible is behind bars," Sarasota County Sheriff Tom Knight announced. "What led to his arrest is unlike anything you’ve heard in the state of Florida. It is something that continues to surface as law enforcement agencies and technology evolve.”

Luke Fleming was arrested using brand new DNA technologies: phenotyping and genetic genealogy. DNA found on the scene of the crime was used to create a phenotype or a picture of what the killer could possibly look like. Then genetic genealogy linked that same DNA from the scene to Fleming’s family tree, ultimately connecting him to the murder. The technology was developed just six months prior to that by Parabon NanoLabs.

“It is becoming more and more popular," Dr. Ellen Greytak, director of bioinformatics for Parabon NanoLabs said. "Of course every time we solve a case and someone announces, ‘I’m not sure we could have solved this without these new tools,’ then other agencies start thinking, ‘are there cases that we have that have DNA?’”

Eleven weeks after the sheriff’s office made their cold case announcement came closure for the family of another Sarasota murder victim, Judith Doherty.

“Judith was the victim of an extremely violent homicide, being beaten and then strangled to death,” Sarasota Police Department detective Anthony DeFrancisco described.

DNA was also the key in providing closure for this case.

It was 2009, 21 years after her death, when Doherty’s body was sent to FDLE. State investigators recovered a man’s DNA from the body.

“This DNA was entered into CODIS, which is the Combined DNA Index System, and gave a match to the suspect David L. Stevens," DeFrancisco announced.

It left many to wonder: why did it take from 2009 to 2018 to close the case?

“When you test something for DNA, even if you get a hit, that’s just the beginning," DeFrancisco explained. It was just the beginning of the investigation. It took several years of interviews and excluding people from the crime scene to get where we are today."

It was 2011 when DNA evidence really started to play a role in investigations for law enforcement. That’s when the state made it mandatory that anyone arrested for a sexual assault or homicide be swabbed and their DNA be put in a federal data base.

Dr. Matt Thomas, a professor at the State College of Florida Manatee-Sarasota, specialized in DNA testing and worked with local law enforcement for years. Back in 2011, he was helping decode suspects' DNA.

“Things really took off in that time period because the human genome project was getting wrapped up and a lot of the equipment and technology that was gained from the human genome project really aided how law enforcement could use and improve on DNA technology," Thomas recalled.

Thomas now trains the future forensic investigators. Knowing where DNA technology has come from, he sees this as only the beginning of the evolution.

“In the last five years it’s really come on the map and people are excited to work with it,” Thomas said.

Investigators also appreciate how far DNA technology has come.

“DNA is the key to solving many of these cold cases," DeFranscisco said. "Without the DNA and without the testing that they do now, we wouldn’t be having this conversation.”

The Sarasota County Sheriff’s Office is now looking to use this same DNA technology to solve two other cases, including the Walker murders. A family of four was killed in December of 1959 in Osprey. DNA evidence has already ruled out possible killers, but now, it may lead investigators to the person or persons responsible.

At Sarasota Police Department, investigators say they are combing through old cases as well to see if new DNA technologies can be used to solve them. They did not specify which cases.

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