Olathe ? A suburban Kansas City man was found guilty Friday of first-degree murder in a fatal attack on his social worker who was stabbed to death during a home visit.

Andrew Ellmaker, 20, of Overland Park, was also convicted of aggravated battery for injuring his mother, Sue Ellmaker, during the attack.

Prosecutors said Ellmaker fatally stabbed Teri Lea Zenner, 26, on Aug. 17, 2004, in the neck, then cut her with a chain saw. Zenner, a Kansas University graduate student who worked for the Johnson County Mental Health Center, was visiting Ellmaker’s house to make sure he was taking his medication.

Zenner’s family members cried and hugged each other as the verdict was read. Ellmaker sat quietly until he was escorted from the courtroom.

Outside the courtroom, Zenner’s father, Andy Mathis, said, “The right decision was rendered today.”

“Teri was a wonderful young lady,” Mathis said. “She was doing a job to try to help others to improve their quality of lives, and she made many sacrifices to do that, including the ultimate sacrifice.

“There is no punishment in this world that will offset what happened to Teri.”

Defense attorneys, who called no witnesses of their own, had asked jurors earlier in the day to convict their client of second-degree murder, saying Ellmaker was incapable of planning the slaying and that Zenner was already dead when he retrieved the chain saw from his bedroom.

“Was this intentional? Yes,” defense attorney Patrick Lewis told the jury. “Was it premeditated? Absolutely not.”

Lewis contended Ellmaker, who has a history of mental illness, “just snapped.” He did not immediately comment on the verdict.

Stephen Maxwell, Johnson County deputy district attorney, said Zenner was “savagely murdered.”

“This is no accident; this was an intentional act,” Maxwell told the jury. “This particular case was in fact premeditated.”

Maxwell said Ellmaker lured Zenner to his bedroom that afternoon and held her at knifepoint before stabbing her in the neck three times as his mother begged him to release Zenner.

During a pretrial hearing, a doctor testified that Ellmaker had been diagnosed with schizotypal, a personality disorder. But Ellmaker’s attorneys did not to use their client’s mental illness as a defense.

On Thursday, jurors heard a taped interview in which Ellmaker admitted to a detective that he killed Zenner, but he had no reason why.

District Judge Peter V. Ruddick ordered Ellmaker held without bond and scheduled a presentencing hearing July 19. Maxwell said he would seek a so-called “hard 50” life sentence for Ellmaker, meaning he would be ineligible for parole for at least 50 years.

Matt Zenner, 30, had been married to Teri for about three months when she was killed. He said attacks on social workers need to be dealt with quickly and effectively.

“Anytime something happens to social workers, this needs to be taken seriously, like with police officers.”