William Camuti, the Sudbury resident charged with attempted murder, is being held for evaluation at Bridgewater State Hospital, a spokesman told Sudbury Patch.
The spokesman did not go into detail as to why Camuti was there.
He is being held without bail until his next court date on Sept. 10 at 2 p.m.
During Tuesday's hearing, which Camuti did not attend, Concord District Court Judge Cathy Campbell briefly discussed a question about his competence to stand trial.
Camuti's lawyer, Robert Saltzman, refused to elaborate on the competency and other questions about his client.
Camuti is facing several charges in connection with the death of Stephen Rakes, a witness in the Whitey Bulger trial, including attempted murder.
Camuti allegedly laced an iced coffee from McDonald's in Waltham with two teaspoons of potassium cyanide, then drove Rakes around for several hours before dumping his body in Lincoln, where it was found on July 17.