GAITHERSBURG, MD -- Police in Montgomery County are thanking a Reston DNA testing company for an arrest in a cold case Friday. Parabon NanoLabs' genetic genealogy technology pointed investigators to Marlon Michael Alexander of Germantown, suspected of raping three women between 2007 and 2011.

"It's emerging technology," said Montgomery County Police Chief J. Thomas Manger in a news conference. "I think this is the really fascinating part of this investigation."

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"I don't think people know that out here in Reston there's this little technology company that's solving 30 to 40 year old cold cases," said Dr. Ellen Greytak, one of Parabon's lead geneticists. She showed WUSA9 the technology back in July.

Parabon's pioneering use of DNA testing technology combined with genealogy has helped police find suspects in dozens of decades-old cold cases including the Golden State serial killer.

Greytak stressed that old DNA testing matched only close relatives. Parabon uploads DNA to a public database to find relatives as distant as third cousins. The company's genealogist then rebuilds a family tree using public data. This generates new leads to find family members so police can get closer to an arrest.

"All of this has really come together into a perfect storm that has made this technology now possible," said Greytak.

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Montgomery County Police say in this latest case, Parabon provided investigators with two possible relatives. Police say they had to close the loop by creating a family tree, finding Alexander, and obtaining a warrant to get a DNA swab from him.

"It gave us the break in this case," said Chief Manger.

DNA data does not come from sites like 23andMe or Ancestry. In fact, Parabon cannot search them since they are databases by private companies. You can upload your own DNA to the GEDmatch database Parabon uses. Volunteering means more chances to close cold cases.

"We're finding that we're really able to make a huge difference," said Greytak.