Police said Ernesto Ramon Mercado, who may have been a rideshare driver, targeted young women living in off-campus shared residences. He's linked to crimes in the Georgetown and Glover Park area, and one near the University of Maryland.

A Northern Virginia man could get up to life in prison if he’s convicted of a string of sexual assaults dating back more than a decade. Police say he targeted students at two D.C.-area universities. He was arrested due to new technology and the work of a special unit working with the U.S. Attorney and others to close sex assault cases.

Ernesto Ramon Mercado, 54, of Arlington, is charged with first- and second-degree sexual abuse in connection with a series of home invasion rapes. He’s linked to a total of six assaults between 2008 and 2012.

“These cases stem from six unsolved home invasion rapes,” Metropolitan Police Department Chief Pamela Smith said. “Five of these crimes occurred in the Georgetown, Glover Park area of Northwest D.C. and one near the University of Maryland in College Park.”

Investigators say Mercado targeted young women living in off-campus shared residences and struck late at night or before dawn.

“In each case, Mercado likely identified his victims through stalking and Peeping Tom activities,” said MPD detective Alexander Mac Bean.

Police say he’d pick intoxicated victims, usually as they walked home, and would wait till the victim was asleep to break in or get in through an unlocked door.

The offender came to be known as the "Georgetown cuddler," but the lead investigator in the case says that term belies the seriousness of the crimes he’s charged with and the harm the victims have suffered.

How DNA and genealogy helped police find the suspect 

Police got DNA from the scenes. While they couldn’t identify who it came from, they knew it was from the same person.

Court documents show police zeroed in on Mercado through DNA profiles submitted to a consumer genealogy service. It's an investigative tool known as genetic genealogy. Police can look up DNA profiles found at a crime scene to find people who are related to the suspect, narrowing down the pool of potential perpetrators.

It’s possible that a relative of Mercado’s was creating a family tree, and police followed the branches as the cold case heated up fast.

Police staked out Mercado's Arlington home and got a warrant for his DNA on Monday.

“We obtained that sample yesterday morning, submitted it for rapid DNA analysis — another tool that has only recently come into existence — and had a DNA match by early afternoon,” U.S. Attorney Matthew Graves said.

“The reward from a case like this is being able to tell a victim years later that we’ve identified the perpetrator that committed this crime,” Mac Bean said.

When Mercado was arrested, time was of the essence. Investigators found that he may have been a rideshare driver. They considered the possibility that he could seek more victims through that work.

Police hope that by releasing pictures of Mercado, anyone else who’s had an encounter with him will come forward.

Police believe Mercado is responsible for dozens of sexual assaults, burglaries and voyeurism cases and there may be additional victims. Anyone with potentially relevant information or who may have been the victim of a related attack is asked to contact police.