A major break in an almost 30-year-old cold case came down to one piece of evidence - DNA.

The FBI's Investigative Genetic Genealogy Team helped Nassau police identify Tanya Denise Jackson and her daughter Tatiana Marie Dykes, thanks in part to major technological advances in DNA identification.

Jackson's torso was found in Hempstead Lake State Park in 1997. Her and her daughter's remains were found near Ocean Parkway in 2011.

"The IGG team combines crime scene DNA with traditional genealogy research and historical records to generate leads to identify unknown DNA which is what happened in this particular case,” said Christopher Raia, the FBI New York Field Office's assistant director in charge.

Pace University Law School Professor and former prosecutor Bennett Gershman says investigators likely turned to a DNA database to connect the dots.

"There are huge databases of DNA, and that's obviously the first source that they would go to,” he said.

John Jay College adjunct professor and retired NYPD Detective David Sarni says the preservation of evidence also played a huge role in the discovery.

"They're able to get possible relatives related to the person from DNA typing, then looking and seeing if that DNA and then talking to those who might be possibly typed to them,” he said. “Retest it, reevaluate it, and finally get an identification."

Experts say the process to get to the point of identifying a victim is a very complicated one.

"It's very, very nuanced. It's very complicated to do that kind of investigation that Nassau has been doing in this case,” said Gershman.

Experts say the hard part, the search for a killer, continues.

Crime Stoppers is offering a reward of up to $25,000 for information.