A teen accused of killing his classmate on the day of the junior prom has entered an insanity plea.

Christopher Plaskon, 17, appeared in a Connecticut court today to plead not guilty in the April 2014 stabbing death of 16-year-old Maren Sanchez by reason of insanity. He is being tried as an adult in the case.

Authorities say Plaskon stabbed Sanchez to death just hours before their junior prom. Investigators believe he may have been angry because she wouldn’t go to the prom with him.

“Anger does not mean insane […] it does mean motive though,” Fox News legal analyst Lis Wiehl said today on “Happening Now.”

Read more from the Associated Press:

Judge Frank Iannotti approved a motion by Milford State's Attorney Kevin Lawlor to allow the prosecution to have its own expert evaluate Plaskon's mental health and continued the case to July 7. The order came after Plaskon's lawyers filed notice Monday that they were planning a defense of "mental disease or defect and/or extreme emotional disturbance."

Lawlor indicated in court documents that the state would hire a Yale University forensic psychiatrist.

Richard Meehan, an attorney for Plaskon, said experts hired by the defense examined Plaskon, but he declined to say what they found. Meehan has said Plaskon was taking anti-psychotic and anti-anxiety medications.

"The focus here is on mental status," Meehan said after the court proceeding.

Police have said they were looking into whether the attack was related to Sanchez's refusal to be Plaskon's date to the junior prom.

Sanchez, a member of the National Honor Society who was active in drama and other school activities, had been focused on prom in the days before her death. She had posted a photograph on Facebook of her blue prom dress and was looking forward to attending with a new boyfriend.

Authorities say Plaskon attacked Sanchez in a hallway on the morning of the prom, stabbing her in the neck and torso. Afterward, Plaskon told a police officer: "I did it. Just arrest me," according to police.

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