WASHINGTON — Police in Montgomery County identified a suspect in a series of cold case rapes — including of an 86-year-old woman who was attacked in a senior living center — using an innovative technology that matches DNA with profiles on online genealogy sites, officials said Friday.
Police arrested Marlon Michael Alexander, 39, of Germantown, on Wednesday, charging him with first-degree rape in connection with the series of attacks that stretch back more than a decade.
Thanks to DNA evidence, Montgomery County said they always knew the same man was responsible for breaking into three homes in Germantown and Gaithersburg and attacking the women inside. In one case, the same woman, a 68-year-old Germantown woman, was attacked in her home twice within six months.
But they didn’t know to who the DNA belonged to.
Authorities said Friday the break in the case came after Montgomery County police partnered with Parabon NanoLabs, a private company that has built a database of DNA samples submitted by users of online genealogy sites, such as Ancestry.com. That company also worked with police in California to help identify a suspect in the Golden State Killer case earlier this year.
That technique turned up the names of several people whose DNA samples were similar to the rape suspect, Police Chief Tom Manger told reporters Friday. Using the data provided by Parabon, detectives reached a distant relative of Alexander’s in Georgia, who was able to provide information about the family. A detective who had experience doing family searches using genealogy websites then went to work, combing through census records and online obituaries to essentially build a family tree that would lead to the suspect, Manger said.
That family tree led to Alexander, he said.
Police obtained a search warrant last week for a DNA sample from Alexander. The sample was analyzed by the department’s crime lab and determined to be a match, he said.
In addition the rape charges, Alexander is charged with attempting to commit a sexual offense and first-degree burglary since police said he forced his way into the women’s homes.
The series of attacks police said Alexander is linked to dates back to 2007.
The first case took place in August of that year, when police say a man forced his way into the home of a 25-year-old woman on Lost Knife Circle in Gaithersburg. According to police, the man threatened to shoot the woman if she didn’t perform a sex act. The woman said she fought off her attacker and he ran off.
On June 19, 2010, during the early morning hours, a man forced his way into the Beaconfield Terrace home of a 68-year-old woman in Germantown according to police. Investigators say the victim was raped as her attacker held a weapon to her head. The same woman was attacked again on January 5, 2011 by the same man, almost a year later according to police.
On August 21, 2010, police said the same man, armed with scissors, raped an 86-year-old woman at the Churchill Senior Living Center on father Hurley Boulevard in Germantown. Manger said that victim has since died.
All four cases were connected by DNA collected by investigators. That DNA was analyzed by Parabon NanoLabs, Manger said.
Detectives are looking at other unsolved rape cases in Montgomery County as they believe it is possible he could be connected to other sexual assaults in the county.
Alexander is being held without bond and will have a bond review Saturday in Rockville District Court.
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