A Dorchester Municipal Court judge on Friday ordered 20 days of observation at Bridgewater State Hospital for Zachery Grandy, 22, arrested Thursday on charges he beat his mother, Gisel Thomas, to death in an apartment on Columbia Road in Dorchester.

Judge Michael Bolden agreed with a request from Grandy's attorney, Keith Halpern, to have Grandy's initial interviews at Bridgewater videotaped to show the extent of what Halpern called Grandy's psychosis before any drugs kick in. "He's extremely psychotic," Halpern said.

A court clinician who interviewed Grandy before his arraignment recommended observation at Bridgewater for Grandy and said he had a history of mental illness.

Bolden also ordered Grandy held in lieu of bail until at least an April 1 court date.

Normally, prosecutors seeking imprisonment without bail have to recite a statement of the case, but Bolden agreed with a request from Assistant Suffolk County District Attorney Amy Martin to impound the police report until at least April 1, both because the investigation is ongoing and to redact the names of any witnesses and family members; so all she did say about the case was that the beating may have begun as early as Wednesday night.

Grandy appeared in the prisoner dock with the usual cuffs and leg chains but he as he stood during the arraignment, he was also held by two court officers, with two more standing right behind them. He spent much of his arraignment looking at family members sitting in the courtroom.

Police say they responded to a report of a disturbance around 2:20 p.m. Thursday at 357 Columbia Rd., where they found both Grandy and his mother's body.