Charles Curtis, a drifter accused of murdering Judith L. DeMaria on a Loudoun County bike path more than two years ago, stalked his victim from his car, then beat her and cut her throat with a razor knife, according to evidence presented by the prosecution yesterday at a preliminary hearing in Leesburg.

After hearing testimony from Loudoun sheriff's deputies about statements Curtis allegedly made to them about the case, General District Judge Archibald Aiken ruled that there was probable cause to allow a grand jury to decide whether Curtis, 28, should stand trial on a charge of first-degree murder.

Curtis' attorney, Fred Hoybach of Fairfax, told the court that there were questions about his client's sanity and competence to stand trial, and asked that Curtis be given a psychiatric evaluation. Hoybach said his client has a "history of instability" and had spoken of "having visions . . . of having died and . . . of having talked with the Lord."

DeMaria, 27, a tennis instructor at the Capitol Courts Racquet & Fitness Club in Sterling, disappeared Aug. 2, 1985, during a midday jog on the Washington & Old Dominion bike trail. She was last seen near a bridge that crosses Broad Run Creek.

The day after her disappearance, deputies found what one described as "a substantial amount of blood" in a nearby field. Tests showed the blood could have been hers.

Authorities were stymied in their investigation until last month, when Curtis contacted a Loudoun sheriff's deputy and reportedly "admitted" to the slaying, according to court records. Deputies said yesterday that Curtis first said that someone else had raped and killed DeMaria.

Curtis, described as being from Martinsburg, W.Va., was charged with murder on Sept. 10, a few hours after deputies found badly decomposed remains in a shallow grave not far from where DeMaria was last seen.

Deputy Robert Turner testified yesterday that Curtis led investigators to the wooded site and began screaming, "There she is!"

Authorities began digging and unearthed remains that were later identified as those of DeMaria.

Investigator Jay Merchant testified yesterday that Curtis told him he had planned to rape DeMaria because she "looked good."

The coroner was unable to determine cause of death and whether DeMaria had been raped.

According to Merchant's testimony, Curtis said he watched DeMaria from his car from several vantage points, then parked and hiked to a spot where she would cross.

"He stopped her and asked her for the time and directions," Merchant testified.

Curtis said he then hit DeMaria and choked her until she was unconscious before dragging her to a wooded spot, Merchant testified. She awoke and there was a brief struggle, Merchant said Curtis told police, after which Curtis cut her wrist. When that did not kill her, Curtis said he slashed her throat, Merchant testified.

Curtis told deputies that he washed off the blood in a nearby stream and returned to where the body was, Merchant testified. He then wrapped the body and drove it to another location near Sterling, where he left it, Merchant said. After a few days, Curtis returned and buried the body, Merchant said Curtis told deputies.

Since Curtis' arrest in the DeMaria case, Fairfax County police have questioned him in connection with the death of Eige Sober-Adler, a 37-year-old Kensington woman whose badly beaten body was found Sept. 8 near the site where DeMaria's grave was found a few days later.

Curtis is being held without bond at the Loudoun County Adult Detention Center. The grand jury is scheduled to meet Oct. 13.