Brian Nichols contends he was delusional and mentally unbalanced the day he went on a rampage three years ago and killed four people.

Now Nichols, scheduled to go on trial for his life next month, will get a chance to convince a prosecution psychiatrist he was out of his mind that day.

PHOTOS • A look at the case 2005-present • Penalty phase | Verdict • Weeks in court: 1 | 2 | 3 | 4 | 5 | 6 | 7 • Interactive graphic: The 2005 shootings • Video: Nichols' confession MORE STORIES 4 years after attacks, courthouse lacks security plan  Gwinnett won't prosecute Nichols for kidnapping  Feds won't seek death penalty for Nichols  In prison, cellphone is coveted contraband  Police reveal little about Nichols manhunt errors  Nichols trial holdouts: 'Show me something'  Nichols says he was at war with U.S. government in taped confession AJC's full trial coverage RELATED LINKS Atlanta news Georgia and metro news

Superior Court Judge James Bodiford ruled Wednesday that Dr. Robert Philips could take as long as 18 hours, over a three-day period, testing and questioning Nichols at the DeKalb County jail where he is held awaiting trial July 10.

Nichols is accused in the March 11, 2005 shooting deaths of a Fulton County judge and three others.