Sixteen-year-old Philip Chism was back in court Wednesday as the jury in his murder trial heard from a mental health expert who diagnosed him with psychosis.

Danvers High School let out early so prosecutors could show jurors where Chism killed Colleen Ritzer. The tour included the woods where her body was found, and later places like the Wendy’s where Ritzer’s credit cards were used in the hours after her death.

Before the trip, jurors heard from an adolescent specialist at Worcester State Hospital. Dr. Anthony Jackson testified to diagnosing Chism with major depression and having had a psychotic episode. Jackson prescribed Chism an antipsychotic, and said he was more engaged after taking the drug.

"Mr. Chism also himself noted the change, and asked for a second dose of the medication," Jackson said.

Under prosecution questioning, Jackson acknowledged that he didn’t know when Chism’s psychosis began, and that the illness may have been triggered by stress of the trial. And Jackson admitted other doctors who evaluated Chism thought he was faking symptoms.