The escalation of charges against a couple linked to the December disappearance of a 20-year-old Horry County woman continued this week …

Initially charged with indecent exposure and obstruction of justice last week – and kidnapping earlier this week – husband and wife Sydney and Tammy Moorer have now formally been charged with the murder of Heather Elvis.

The only problem? Elvis’ body has yet to be found – which means prosecutors face a much higher hurdle in proving guilt beyond a reasonable doubt.

Nonetheless, the Moorers stand accused of murdering her with “malice aforethought” – a.k.a. premeditation. It’s not immediately clear whether prosecutors will seek the death penalty, though.

Elvis was last seen on December 17. Her car – a green 2001 Dodge Intrepid – was discovered two days later at a boat landing near Socastee, S.C.

Elvis was believed to have been involved in a romantic relationship with Sidney Moorer, 38, in the months prior to her disappearance. In fact according to a reporter who claims to have interviewed 41-year-old Tammy Moorer a month ago, she stated that Heather Elvis and her husband had sex in her car “a total of three times.”

The Moorers have an open marriage – meaning they are allowed to have multiple sexual partners.

“(Sidney Moorer) ended it when he realized something wasn’t right about her,” Tammy Moorer told the reporter.

The murder charges against the Moorers will be handled by solicitor Jimmy A. Richardson of Conway, S.C. Attorney Patrick McLaughlin of Florence, S.C. will represent Tammy Moorer, while attorney Kirk Truslow of Myrtle Beach will represent Sidney Moorer.