Cracking the case: New DNA technology solves murder, rape case in Sarasota

SARASOTA (WWSB) - A brand-new method of analyzing DNA evidence is cracking cold cases wide open nationwide, including one right here in Sarasota. Genetic genealogy has solved twenty rape and murder cases to date in just the six months it’s been used as a tool by law enforcement. Without it,an alleged killer would still be living right in our backyards.

On March 29, 1999, Deborah Dalzell had just moved into her brand new home on Country Meadows Lane where she lived alone. That night Dalzell was raped and brutally murdered.

It was a case that shocked residents in Sarasota.

“This woman was a worker, minded her own business, didn’t live in an area where you think something like this would happen," Captain John Walsh of the Sarasota County Sheriff’s Office said.

But it did, and for 19 years the killer got away with it.

“People expect the Sheriff’s Office to figure these things out," Captain Walsh said. “I’m sure several times throughout the years investigators thought they had it figured out and then were let down.”

September 16th would be the last day Dalzell’s alleged killer would know freedom. 39-year-old Luke Fleming, a man who lived just down the road from Dalzell at the time, was linked to the crime using evidence police had all along: semen that was left on the scene.

The break in the case came three years ago after Captain Walsh was inspired by a magazine article.

" I read a National Geographic article in 2015 about phenotyping DNA, and I went, ‘huh I wonder if we can use that,'" he recalled.

Walsh and his team called Parabon NanoLab, the company behind this new technology, called phenotyping.

Dr. Ellen Greytak is the director of bioinformatics at Parabon NanoLabs. She and her team started using phenotyping four years ago to help law enforcement generate new leads in a case.

Phenotyping takes DNA that a suspect left on a crime scene and uses it to predict what that suspect looks like. It can identify hair and eye color, along with face shape, which the company uses to produce a composite for police.

One thing phenotyping can’t do is predict a persons age or weight.

Phenotyping isn’t directly what led detectives to Fleming. It was a combination of that and what’s called genetic genealogy.

The same lab that developed phenotyping can also take a suspect’s DNA, and compare it to DNA voluntarily submitted by people who are researching their genealogy.

“If you do that your DNA stays in those private data bases. It is not used for law enforcement," Greytak explained. "Law enforcement does not have access to those private databases. However, if you took a test at 23andMe and your cousin took one at Ancestry, you couldn’t compare them because those data bases are separate. They’re private, but if you wanted to be able to compare to one another, you could both download your data and then upload to a database called GEDmatch which is a public database.”

GEDmatch is the database that Dr. Greytak and her team use to find similarities between the suspect’s DNA and other users' DNA.

When they find someone that closely resembles the suspects DNA, genealogists will research the families to find their suspect.

It’s a lengthy process that could take months or years.

“In a lot of these cases, we are able to give law enforcement a name or a set of brothers, but this is still just a lead," Dr. Greytak said. "Even if we tell them it has to be this person or one of these people, law enforcement still has to follow up on that and do a traditional investigation.”

That’s what the Sarasota County Sheriff’s Office did to find Fleming.

DNA technology is constantly evolving and could make law enforcement’s job even easier in the future.

“What we are seeing is some departments are thinking, ‘if this can give me answers on 30 year old DNA, then it can give me answers on three month old DNA,’” Dr. Greytak explained.

Not only that, but Dr. Greytek thinks in the future, DNA technology will also be able to identify age.

For Captain Walsh he sees endless possibilities.

“It is even becoming portable where you go to a scene and compare DNA. That technology I think will exist," Captain Walsh explained. "That’s a long way away, but I think that’s where it’ll go, where it’s portable. I can at least exclude people immediately from certain crimes.”

The Sarasota County Sheriff’s Office is now looking to use this same DNA technology to solve the Walker murders. A family of four was killed in December of 1959 in Osprey. DNA technology already ruled out several killers in this case.