MARIPOSA, Calif. (AP) - Prosecutors said Monday they will seek the death penalty against a man if he is convicted of killing three Yosemite Park tourists.

Cary Stayner, already serving a life sentence in the killing of a park naturalist, pleaded innocent to three counts of murder and a number of additional charges in the deaths of the tourists.

Prosecutor George Williamson said he will seek the death penalty in the February 1999 killings of Carole Sund, her daughter Juli, and family friend Silvina Pelosso of Argentina.

The announcement had been anticipated after Mariposa District Attorney Christine Johnson brought in Williamson, a Solano County prosecutor who specializes in capital punishment cases.

Stayner, 39, was sentenced to life in prison last year after confessing to murdering Joie Armstrong, 26, who led children on nature tours in the park. Federal prosecutors dropped their bid for execution as part of a plea bargain.

Stayner admitted the killings during a six-hour taped interview with FBI agents in July 1999 shortly after Armstrong's headless body was found in a creek near her cabin in the park. An excerpt of the tape was played at a preliminary hearing last month in which Stayner described how he preyed on the tourists and killed them one by one.

He said he had fantasized of killing for months and said he turned the dream to reality when he saw ``easy prey'' through a window at the Cedar Lodge, where he worked as a handyman just outside the park.

Carole Sund's father said he favors the death penalty for Stayner because the crimes were so heinous. Stayner allegedly repeatedly raped Juli Sund and tried to rape Pelosso.

``The death penalty ... I understand is administered with muscle relaxants and things that show no pain,'' Francis Carrington said. ``I would have prayed and hoped our children could have gone as easy, that he could have showed some compassion himself.''

Stayner's trial is set for Feb. 25.