PORTLAND — Psychiatrists and psychologists have taken center stage as the murder trial of Chad Gurney nears its conclusion at Cumberland County Superior Court.

Dr. Peter Donnelly, a psychologist who works on contract for the State Forensic Service, has been on the stand this morning. In his opinion, Gurney was deeply troubled and possibly delusional when he killed 18-year-old Zoe Sarnacki on May 25, 2009, but he was legally sane and understood the wrongfulness of his actions.

Dr. Harold Bursztajn, a Harvard Medical School psychiatrist hired by the defense, testified on Tuesday that he believes Gurney was psychotic and so delusional that he should not be held criminally responsible.

Justice Roland Cole will decide Gurney’s legal fate, because he waived his right to a jury. The trial is expected to conclude on Thursday.