Suspect in 1998 Georgetown-area murder in custody

November 20, 2019

Giles Daniel Warrick, the suspect in a murder in Georgetown and several rapes in the D.C. metro area between 1991 and 1998 was detained on Nov. 13, and is now in police custody. The decades old investigation was aided by the use of genetic genealogy. 

Warrick, 60, was arrested at his home in Horry County, South Carolina and charged with six counts of first-degree rape in Montgomery County, Maryland.

Known as the “Potomac River Rapist” because of the geographic area of the attacks, Warrick has been linked by DNA evidence to eight sexual assaults in Montgomery County, and two sexual assaults and a murder in Washington. Two other rapes are linked to Warrick due to the way the crimes were committed. 

The victims ranged in age from 18 to 58. The Potomac River Rapist would often cut phone lines, force his way into homes, cover the victims’ heads, before committing sexual assault.

In 1998, Christine Mirzayan, a then-29-years-old National Academy of Sciences fellow living in student housing at Georgetown University, was walking home from a cookout in the Georgetown neighborhood when she was sexually assaulted and murdered with a 73-pound-rock in the woods. 

In 2011, the Montgomery County Police Department (MCPD) and the Metropolitan Police Department (MPD) were able to link eight of the cases using DNA. In conjunction with the FBI, they formed a task force and put up billboards with a sketch of the suspect at bus stations and other locations in 15 cities along the East Coast. The FBI also launched a website modeled after the efforts that led to the arrest of former Boston mobster James “Whitey” Bulger.

However, it took the development of technologies like genetic genealogy and public genealogy services to finally crack the case. According to Virginia forensic genealogy company Parabon Nanolabs, genetic genealogy “is the combination of genetic analysis with traditional historical and genealogical research to study family history,” and that for forensic investigations, “it can be used to identify remains by tying the DNA to a family with a missing person or to point to the likely identity of a perpetrator.

According to Sgt. Chris Homrock, head of the MCPD’s cold case unit, detectives submitted a genetic profile they had developed from the evidence at the scene to Parabon Nanolabs. The lab then identified a number of possible relatives, whom detectives interviewed and subsequently learned of Warrick.

Genetic genealogy has dramatically altered the way detectives have cracked cold cases. According to Parabon Nanolabs chief genealogist CeCe Moore, around 100 suspects have been identified using genetic genealogy since the arrest of the suspected “Golden State Killer” in April 2018

Warrick, who refused to talk with authorities after being taken into custody this week, allegedly expressed no remorse when asked about the crimes he had been charged with. 

According to MPD Chief Peter Newsham, Warrick will be extradited to D.C. in order to be charged with first-degree murder and the sexual assaults in the D.C. metro area. 

MCPD detectives are now re-examining local unsolved rape cases to see if Warrick can be connected. 

“Detectives are concerned there may be additional victims in the area given the prolonged period of time that has elapsed involving Giles Daniel Warrick,” read a Nov. 14 MCPD press release

Jason Cuomo
Jason Cuomo is a sophomore in the college studying history and government. In his free time he's probably either obsessively reading FiveThirtyEight or making oddly specific playlists.

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