A judge said Tuesday a confession by a Danvers teen that he murdered his high school math teacher could not be used in his trial.

Court documents said statements Philip Chism made at the Danvers police station would not be permitted because the court could not find that he knowingly waived his Miranda rights.

In the videotaped questioning by police, Chism admitted to killing his teacher, Colleen Ritzer, who was found dead in the woods behind Danvers High School.

Court documents said Chism showed disinterest in speaking to Danvers Police and his mother requested an attorney multiple times. Additionally, Chism "did not appear to be fully engaged as the officers explained his Miranda rights to him.

The judge also ruled that cell phones found after the murder would also be suppressed because the location of the phones was only discovered after Chism’s interview.

Colleen Ritzer’s family released a statement on the ruling:

“Our family is grateful to the many members of law enforcement who tirelessly searched for our daughter and sister, Colleen. We respect the court ruling and we are confident that law enforcement acted responsibly and lawfully. We are also confident in the ability of the District Attorney’s Office to successfully prosecute the individual charged with this horrific crime so that justice is served for Colleen and our family.”

Stay with 7News and WHDH.com for updates to this developing story.

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