Convicted killer Gary Michael Hilton pleaded not guilty Monday in a North Carolina federal court to allegations he kidnapped and murdered an elderly couple in 2007.

Already serving a life sentence for a Georgia slaying and awaiting execution in Florida for another, Hilton could face the death penalty for the double murder of John and Irene Bryant who disappeared while hiking in the Pisgah National Forest in North Carolina.

The case is being handled in federal court because the Bryants were killed in a national forest.

A grand jury in Charlotte indicted Hilton in June for the couple's murder. According to the indictment, Hilton stalked unexpected victims on hiking trails with the intention of robbing them.

Just days after the Bryants were reported missing, $300 was withdrawn from the couple's bank account.

Hilton is serving a life sentence for the January 2008 slaying of Meredith Hope Emerson in the Dawson Forest Wildlife Management Area.

Dawson County Sheriff's Lt. Col. John Cagle was the lead investigator on the Emerson case before he retired from the Georgia Bureau of Investigation.

Cagle said the evidence Georgia investigators recovered during the Emerson case "will greatly enhance North Carolina's ability to convict Hilton in the deaths of John and Irene Bryant."

Earlier this year, Cagle was in a Florida court as Hilton was convicted and sentenced to death for the 2007 murder of a Cheryl Dunlap.

"I plan to go to North Carolina, just like I did for the Florida trial," Cagle said.

Authorities have also named Hilton the prime suspect in the slaying of 27-year-old Michael Scot Louis, whose body was found at a Florida state park about the same time as the other victims.

Hilton has not been charged in that case.

The trial in North Carolina is set to begin Sept. 6.