Saddam Hussein's execution on Dec. 30 prevents him from being put on trial for his most serious crimes – genocide against the Kurds and the use of poison gas in the Iran-Iraq war. As many as 100,000 Kurds were killed in 1988. Why then was Saddam executed for killing 148 men and boys in the Shiite town of Dujail in 1982?

Human rights activists say the answer is clear: the Bush White House wanted to prevent Saddam from offering evidence of US complicity in his crimes as a defense. It's the same reason the Saddam trial was held under Iraqi auspices rather than in the International Criminal Court: ''It's to protect their own dirty laundry,'' Kenneth Roth, the executive director of Human Rights Watch, told the New York Times in 2004. ''The U.S. wants to keep the trial focused on Saddam's crimes and not their acquiescence.''

Human Rights Watch has done more to document Saddam's genocide of the Kurds than any other organization. Their 1993 report remains the most detailed and meticulous account, based on extensive interviews with eyewitnesses and analysis of Iraqi government internal communications. During the Iran-Iraq war, Saddam had lost control of Kurdish regions because all his troops had been sent to the battlefields. But as that war came to an end in 1988, he launched his "Anfal" campaign against the Kurds, leveling thousands of their villages and killing 50,000-100,000, mostly by bombing and mass executions.

Saddam's most notorious atrocity was his use of poison gas against Kurds in the town of Halabja in 1988, killing at least 5,000. George Bush cited that attack – "gassing his own people" — as part of his argument for a US war against Iraq. However back in 1988 the US worked to prevent the international community from condemning Iraq's chemical attack against Halabja, instead attempting to place part of the blame on Iran. [See Dilip Hiro, "Iraq and Poison Gas," TheNation.com, Aug. 28, 2002.]

The US had supported Iraq in the Iran-Iraq war, on the grounds that Iran was a greater threat to the US after the rise to power of the Ayatolla Khomeini.

When the Iran-Iraq war ended in 1988, Saddam's genocide against the Kurds was no secret. The US Senate passed a bill to penalize Baghdad for violating the Geneva Protocol on Chemical Weapons – they did it virtually without opposition, in a single day.

But the Reagan Administration killed the bill. Political scientist Bruce Jentleson of Duke University told the BBC that they did it "for two reasons. One, economic interests. In addition to oil, Iraq at that point had become the second-largest recipient of government agricultural credits to buy American agriculture . . . . And secondly was this continual blinders of the enemy of my enemy is my friend."

During the Iran-Iraq war, Saddam used chemical weapons, most obviously in his 1988 campaign to retake the Fao Peninsula. The had been banned since the 1925 Geneva Convention. His trial for that crime has also been prevented by the execution.

Again his defense was likely to have been that the US did not object at the time. Walter Lang, senior defense intelligence officer for the United States Defense Intelligence Agency at the time, told the New York Times in 2002 that "the use of gas on the battlefield by the Iraqis was not a matter of deep strategic concern" to Reagan and his aides, because they "were desperate to make sure that Iraq did not lose."

Trials in Baghdad for other Iraqi leaders accused of genocide against the Kurds and violation of the Geneva Protocol on Chemical Weapons may be held. But as Antoine Garapon, director of the Institute for Advanced Legal Studies in Paris, told the New York Times, even if others stand trial, "the person deemed most responsible would never face judgment."

Thus Saturday's execution of Saddam Hussein seems less an act of justice for his victims and more an effort to cover up US complicity in his regime.