Jack Ronald Jones, one of two men accused of killing Frostburg State College senior Stephanie Ann Roper in St. Mary's County on April 3, told police he hit her with a chain and set her afire because "I was scared and didn't know what to do" when she tried to flee her abductors, according to testimony at Jones' trial here today.

"I didn't mean to kill her," Jones said in a signed statement to police read into the record by Cpl. Thomas Bowers of the Maryland State Police. Bowers participated in questioning the suspect several days after Roper, home for the weekend before Easter, was kidnaped, raped and murdered at the end of a lonely county road.

"I wasn't trying to kill her," Bowers quoted Jones as saying. While the 26-year old defendant listened to his words read aloud from the witness stand, Bowers continued with Jones' April 11 statement: "I just didn't know what to do . . . It's just what happened . . . I was scared then and I am scared now."

On Tuesday, an assistant state medical examiner testified that the immediate cause of Roper's death was a single bullet to the forehead.

In his signed statement, Jones acknowledged firing a gun once but said, "I didn't know she was shot." In conversation with another officer, recalled on the witness stand yesterday, Jones was quoted as saying he fired the weapon twice.

Jones' case is being heard by a jury here in Baltimore County because of pretrial publicity in Southern Maryland that a judge deemed prejudicial to the defense.

Prosecutor C. Clarke Raley and his deputy, George R. Sparling, are pitted against two court-appointed lawyers, E. Allen Shepherd and Gary E. Bair, director of the American University Law School's criminal justice clinic.

Codefendant Jerry Lee Beatty, 17, is scheduled to be tried separately in Anne Arundel County next month. Beatty, who made a statement to police, is expected to testify against Jones this week.

In his opening statement, Raley asserted Beatty will testify that Jones said they must kill Roper after he had unwittingly called Jones by his nickname, "Bump" or "Bumper."

But Jones said in his statement, "I didn't feel I had to kill her. When I hit her [with the chain], I didn't think I'd hit her that hard. I think I was just trying to knock her out and just leave."

Jones acknowledged when questioned as he was giving his statement that he was a volunteer fireman familiar with head injuries. When asked what happens when people are hit on the head with a heavy chain, he replied: "They are usually bust open." Skull fracture and death could result, he acknowledged.

Roper, whose family lives near Upper Marlboro, had spent the evening with a girlfriend at a District of Columbia disco bar and was driving home from the friend's house when her car ran off the road in Southern Prince George's County and Jones and Beatty happened by, according to testimony.

They promised her a ride to her friend's home, according to Jones. Instead, Jones said in the statement, Beatty raped her in the back seat and, after stopping to smoke marijuana on Piscataway Road, they proceeded to an abandoned house near the Patuxent River where each man raped her while the other held a gun.

After he hit her with the chain, Jones said, he went to get gasoline to burn her clothes and pocketbook. When he returned, he said, "she didn't have any pulse, so I poured gas on her, and lit it."