BAGHDAD, Iraq — The trial of Saddam Hussein descended into fresh chaos yesterday when a new judge expelled the former Iraqi president from the courtroom and the defense team announced that it would boycott proceedings.

Within hours of the judge taking over, Saddam launched a tirade against the court and questioned the judge’s authority. When he refused to sit down, Mohammed al-Khalifah ordered him to be escorted from the courtroom.

Mr. Khalifah, a Shiite Arab who was formally deputy presiding judge, took over as the chief judge after the removal of Abdullah al-Amiri. The Iraqi government demanded the change after Mr. Amiri said Saddam was “not a dictator.”

The lawyers said they would boycott proceedings because “the government is interfering in this trial and impacting on its credibility.”

When Mr. Khalifah brought in a replacement team of court-appointed lawyers, Saddam refused to accept them.

As guards approached to take him away, Saddam urged his fellow defendants to leave. In a final outburst, he tried to discredit Mr. Khalifah by accusing his father of being a government spy under his regime. The hearing is expected to continue.

The replacement of the judge has been criticized. Human Rights Watch called it “a clear and damaging violation of the judicial independence” that “jeopardizes the integrity of the court.”

The trial relates to the “Operation Anfal” campaign against Kurdish separatists in 1988, which the prosecution alleges killed 182,000 people.