San Jose, Calif. ? A former motel handyman was convicted Monday of the 1999 slayings of three Yosemite park tourists in a crime that shattered the serene image of one of America’s most treasured places.

Cary Stayner, 41, was found guilty of three counts of first-degree murder and a charge of kidnapping. He could face the death penalty because the jury found the crimes were committed during other felonies, including burglary and attempted rape.

Defense lawyers had conceded that Stayner killed Carole Sund, 42, her daughter, Juli, 15, of Eureka, and Silvina Pelosso, 16, of Argentina, but they said he was insane and asked jurors to convict him of second-degree murder a verdict that would have spared him the death penalty.

The three women had been staying at the rustic motel where Stayner worked as a handyman outside Yosemite National Park.

Their slayings in February 1999 went unsolved for nearly six months until Stayner struck again, snatching Yosemite nature guide Joie Armstrong and beheading her near her cabin in the park. He’s serving life in prison without chance of parole after pleading guilty in federal court to first-degree murder in Armstrong’s death.

“It’s a vindication of our feeling that this definitely is a death penalty case and that it was a horrendous crime,” Carole Carrington, the mother of Carole Sund, said after Monday’s verdict.

Stayner’s lawyers plan to present an insanity defense to try to spare his life. Jurors have already heard extensive testimony from experts that Stayner was impaired by a medley of mental illness symptoms and a deformed brain. At this stage in the trial that evidence was used by the defense to show he didn’t kill intentionally.

In the sanity phase, to begin Thursday, the defense will build on that foundation to try to prove that Stayner didn’t know he was killing or didn’t know it was wrong. If that strategy fails, a third phase of the trial will be held to determine if he should be sent to death row.