ERIE, Pa. (AP) _ A 15-year-old boy charged with killing a teacher at a school dance is psychotic, paranoid and delusional and cannot be treated effectively in an adult prison, a defense psychiatrist testified today.

Andrew Wurst is charged with killing science teacher John Gillette at a middle school graduation dance in Edinboro last April, when he was 14. It was one of a series of school-related shootings that shocked the nation.

A hearing opened today in Erie County Court on whether Wurst should be classified as a juvenile. If that happens, he could be free at age 21. Wurst is now considered to be an adult and could face life in prison if convicted in an adult court.

Dr. Robert Sadoff, who was hired by Wurst's attorneys, said Wurst needs the kind of treatment he can get in a juvenile jail and predicted that Wurst will not be cared for among adults in a state prison. He said people with mental illnesses like Wurst's have prospects for improvement.

``Locking him up doesn't do that,'' Sadoff said.

He said Wurst is convinced that he is the only real person in an unreal world, so he laughs off the seriousness of the murder charge against him. Television cameras recorded the handcuffed Wurst laughing in the back of a police car shortly after his arrest, angering some residents of Edinboro.

Sadoff said Wurst exhibits symptoms of schizophrenia but cannot be diagnosed as having the disease. Psychiatric guidelines reserve schizophrenia for people 18 and older, Sadoff said.

Wurst is also charged with wounding two students and threatening to kill his school principal.

In Pennsylvania, juveniles accused of murder are always charged first as adults. A judge decides later whether the case can be moved to juvenile court.

Wurst is accused of using his father's handgun to shoot Gillette in the back and head. He told a psychiatrist that he was embarrassed earlier that evening when Gillette gave him a door prize at the dance.

If convicted as an adult, he faces life in prison without parole. If convicted as a juvenile, he would automatically be released when he turns 21. Because Wurst is under 16, state law prohibits prosecutors from seeking the death penalty, even if he stands trial as an adult.