BAGHDAD – Saddam Hussein’s cousin, known as “Chemical Ali,” and 14 others went on trial Tuesday on charges of crimes against humanity in the brutal suppression of a Shiite uprising that killed tens of thousands after the 1991 Gulf War.

Iraq’s third trial against former regime officials opened with three of the defendants already sentenced to death in another case.

The Iraqi High Tribunal said the defendants faced the capital charge of crimes against humanity for allegedly engaging in widespread or systematic attacks against the civilian population, and the evidence would include testimony from about 90 victims and witnesses.

Saddam’s cousin and former defense minister Ali Hassan al-Majid, who gained the nickname “Chemical Ali” after chemical attacks on Kurdish towns during the so-called Anfal campaign, entered the courtroom wearing his traditional white Arab robe and a red and white checkered headdress. He sat subdued for most of the trial, only standing once to question the first witness.

Chief judge Mohammed Oreibi al-Khalifa told the men they were charged with crimes against humanity, which court officials said included murder, torture, persecution and random detentions, and carry the maximum penalty of death by hanging.

The charges stem from the aftermath of the 1991 Gulf War, in which the United States drove Saddam’s forces from Kuwait.

Shiites in the south and Kurds in the north sought to take advantage of the defeat, launching uprisings and seizing control of 14 of the country’s 18 provinces. U.S. troops created a safe haven for the Kurds in three northern provinces, preventing Saddam from attacking. But the late dictator’s troops marched into the predominantly Shiite south and crushed the uprising, killing tens of thousands of people.

“The acts committed against the Iraqi people in 1991 by the security forces and by the defendants sitting were among one of the ugliest crimes ever committed against humanity in modern history,” the prosecutor Mahdi Abdul-Amir said in opening remarks.

Sabir al-Douri, former director of military intelligence, told the judge he was in Baghdad during the 1991 uprising and did not visit the south during this period.

Sabawi Ibrahim, who was one of Saddam’s half brothers and head of the feared Mukhabarat intelligence agency at the time of the uprising, defended the regime’s invasion of Kuwait as Iraq’s “historic right” and said the court was illegal because it was backed by the United States.

“This court was established by the occupiers who ignored the international law and invaded Iraq without the permission of the United Nations,” he said.

Ibrahim, who was a presidential adviser when Saddam was ousted in 2003, said the Shiite uprising had been orchestrated by Iran and militant Iraqi exiles sponsored by Tehran.

“Iran failed to achieve its goal in the 1980-1988 war, but it seized the chance in 1991 to kill Iraqis and loot Iraq,” he said.