A 16-year-old Christian school student charged with fatally stabbing his principal told police he spent the night before the attack sharpening a knife, court documents say.

Eduardo Marmolejo (mar-moh-LEH'-ho) is charged with murdering 49-year-old Suzette York, who was stabbed multiple times and left to die in a pool of blood in a classroom at Memphis Junior Academy on Aug. 10.

State prosecutors want to try the teenager as an adult. A court hearing to review mental evaluations and decide whether to move the case out of juvenile court was postponed Wednesday to give defense attorneys another week to finish their own investigation, which includes an independent mental evaluation.

"We're still in kind of a fact-finding process," defense lawyer Autumn Chastain said. "We certainly don't want to rush justice."

Police affidavits obtained by The Associated Press say that Marmolejo told a detective he had planned to kill York since May, and that he chose the third day of classes because he knew they would be alone in a classroom. Marmolejo was one of the oldest students in the small private school, which is affiliated with the Seventh-day Adventist Church.

In an affidavit for a search warrant, Sgt. A.G. Mullins wrote that part of the teen's planning was based on Internet research.

"It may also be based on books, magazines or pamphlets that address close-quarters combat or 'hand-to-hand' combat, knife fighting or other fighting styles," the affidavit dated Aug. 11 said. The officer wrote that Marmolejo had books of that nature in his possession.

Police searched his family's east Memphis home and took two laptop computers, a computer tower, a flash drive, a PlayStation 2 video game console, an iPod, a book titled "Battle," and assorted papers, CDs and DVDs.

Mullins also wrote that he believed Marmolejo had an interest in writing rap lyrics. The detective said the youth wrote rap lyrics, some of them violent, on a homicide office chalkboard and on a piece of paper supplied at his request while he was detained the day of the killing.

The affidavit didn't include the specific lyrics.

Police have said Marmolejo told them he killed York because he did not like her and she had made him angry.

The thin, glasses-wearing teen appeared in court Wednesday in an orange jumpsuit. He is being held without bond. His parents declined comment outside the courtroom.

Special Judge Herbert Lane set the next hearing for Sept. 7.