SANFORD, Fla. - Detectives investigating the 3-decade-old slaying of a Navy recruit used genealogical research involving DNA to track down and arrest a suspect who was a one-time Navy training classmate of the victim, authorities in Florida said Thursday.

Thomas Garner, 59, was arrested in Jacksonville, Florida on Wednesday for the 1984 slaying of Pamela Cahanes, said Seminole County Sheriff Dennis Lemma.

Cahanes was 25 at the time of her death and the two were classmates at the Orlando Naval Training Center, the sheriff said at a news conference.

“It’s extremely bizarre to think that somebody could commit a crime like this, then go on and lead a normal life,” Lemma said of Garner, a dental hygienist.

Cahanes was found beaten and strangled in Sanford, a city near Orlando, in August 1984.

Detectives used genetic genealogical research to develop a DNA family tree that led to Garner’s arrest. He is charged with first-degree murder. Online court records showed no attorney listed for him. He has not been given bond.

As DNA technology evolved over the decades, detectives had regularly submitted samples found on Cahanes’ body in hopes of breaking open a lead, Lemma said.

But it wasn’t until recently that Garner’s DNA was matched to the samples using a genealogy research database. Officials didn’t elaborate further.

Detectives followed Garner around until he dropped a personal item that detectives were able to grab and have tested, Lemma said.

Genealogical research has been increasingly employed by investigators ever since it was used to make an arrest last year in California in the “Golden State Killer” case.