Jerry Lee Beatty, scheduled to go on trial yesterday in the slaying of Frostburg State College senior Stephanie Ann Roper, changed his plea at the last minute to guilty of murder, rape and kidnaping and was sentenced to life in prison.

A codefendant, Jack Ronald Jones, was convicted by a jury of the same offenses last week and also received a life sentence.

Beatty, 17, appeared before Anne Arundel Circuit Court Judge Raymond G. Thieme Jr. in Annapolis and acknowledged his role in the abduction, beating, raping, burning and killing of the 22-year-old Roper last April 3 in St. Mary's County.

The conviction of Jones, 26, by a jury in Towson, Md., followed a week-long trial. He escaped the gas chamber when the jury decided he should receive life imprisonment instead.

Prince George's County State's Attorney Arthur A. Marshall Jr. said yesterday he will seek further indictments against Jones and Beatty in the case because he was upset with the sentences given both men. Both will be eligible for parole consideration in 12 to 15 years.

Marshall said he will seek indictments from a grand jury Nov. 3 on first degree rape and conspiracy to rape charges. Although Roper was killed in St. Mary's County, authorities said the events that led to her death began in Prince George's, and therefore Marshall has jurisdiction.

Marshall said last week that if the death penalty had been ordered, he probably would not be looking into the cases.

The cases of the two men had been removed from St. Mary's County to Annapolis and Towson after defense attorneys contended pre-trial publicity would be prejudicial to their clients.

Both men acknowledged chancing upon Roper in her disabled car in a remote section of Prince George's County, abducting her to St. Mary's County and raping her in an abandoned house, but differed about how she was killed.

Beatty, who cooperated with police after his arrest, testified at Jones' trial that after they raped Roper repeatedly, Jones struck her with a logging chain, shot her in the forehead and set her afire. He said he and Jones had spent several hours consuming beer and drugs before they encountered Roper.

Jones did not testify at his trial, but police testified he told them he did not know Roper had been shot and that he intended to hit her with the chain only hard enough to knock her out. He told investigators he went to get gasoline to burn her clothes and pocketbook, but when he found she had no pulse, "I poured gas on her and lit it."

Jones' attorney, E. Allen Shepherd, told the jury he believed Beatty shot Roper. Beatty denied it but acknowledged that his attorney told him he would likely escape the death penalty if Jones was convicted of firing the fatal shot.