The state Medical Examiner's office in Baltimore identified the body Wednesday from dental records.
An autopsy revealed last week that the woman died of stab wounds. The death has been ruled a homicide.
Police told Miller's family Thursday that the autopsy showed she had been dead four or five months before a Conrail employee found the body in a wooded area, according to Russell L. Younker Jr., Miller's stepfather.
Police would not confirm that information.
That would be consistent with reports that Miller had been missing since the end of November.
Miller reportedly was last seen Nov. 20 in the parking lot of Big Lots on Maryland Avenue.
She was spotted there by her older sister, Younker said.
Miller was believed to have been with Thomas Clifford Wallace, accused in the Aug. 20, 1997, fatal beating of Darrius Allen Fetterhoff, 58, of Grant Street, Greencastle, Pa.
Fetterhoff died Aug. 28, five days after he was found at the bottom of a 90-foot embankment along the Conococheague Creek.
A Washington County grand jury returned a murder indictment against Wallace in October, but that charge was dropped when Miller could not be found to testify.
In February, Wallace was sentenced to 11 years in prison on drug charges.
In June 1996, Miller, then 18, accused former Hagerstown City Police officer Larry Jacob Rowe of holding her against her will at his home, where she said she had gone to have bondage photos taken.
Rowe entered Alford pleas on Dec. 12, 1997, to one count each of fourth-degree sex offense and common law assault.
In an Alford plea, a defendant acknowledges that the prosecution has enough evidence to gain a conviction, but doesn't admit guilt.
He was sentenced to a three-year suspended prison sentence for assault and time served for the fourth-degree sex offense. He was placed on probation for four years and ordered to continue psychiatric counseling and medication.