Judge Laura Ripken granted the defense request Tuesday, ruling that part one would determine if Jarrod Ramos is guilty of gunning down the victims inside the newspaper office.
If he is convicted, the second phase would determine if Ramos is not criminally responsible for his crime — the state of Maryland’s version of the insanity defense.
Ramos has already pleaded not guilty and not criminally responsible.
Prosecutors want to submit Ramos’ tax records dating back to 2003, saying they will show his mental state and prove he is able to tell right from a criminal action.
The defense plans to argue the tax records are confidential and irrelevant.
Ramos allegedly burst into the offices of the Capital Gazette in Annapolis, Maryland last year with smoke grenades and a shotgun and barricaded the doors to stop people from escaping.
Five people were killed, including editors and reporters. Police found Ramos hiding under a desk.
Prosecutors say Ramos had a grudge against the newspaper over a story in which he pleaded guilty to harassing a former high school classmate.
He sued the newspaper for libel and lost, but is accused of continuing to send threatening notes and letters.