MILFORD, Conn. >> A 17-year-old Connecticut boy charged with stabbing a classmate to death on the day of their high school’s prom pleaded not guilty to murder Wednesday.

Christopher Plaskon entered the plea in Milford Superior Court. He also waived his right to a probable cause hearing and elected for a trial before a three-judge panel rather than a jury.

Plaskon’s attorney, Richard Meehan, said after the hearing that he’s investigating a possible mental health defense and said such a defense would be more difficult to make before a jury. Plaskon, whose family attended the hearing, is on anti-psychotic and anti-anxiety medications, Meehan said in court.

Plaskon is charged with killing his friend Maren Sanchez, who was stabbed in April in a hallway at Jonathan Law High School in Milford. The 16-year-old was a member of the National Honor Society who was active in drama and other school activities.

The attack occurred hours before the school’s junior prom. Police are investigating whether it was related to Sanchez’s refusal to be Plaskon’s prom date.

A witness saw Plaskon on top of Sanchez during the attack and tried unsuccessfully to pull him away, and another saw him discard a bloody knife, according to a police affidavit.

Plaskon, his clothes bloody, was taken to the principal’s office, where an officer arrived and asked what happened. "I did it. Just arrest me," Plaskon replied, according to the officer.

Plaskon, who turned 17 last week, is being held on $3 million bond at Manson Youth Institution in Cheshire, where he was placed at a hospital.

He is being prosecuted as an adult and faces up to 60 years in prison with a mandatory minimum of 25 years if found guilty of murder.