Saddam and seven co-accused have been charged with crimes against humanity for the killing of 148 Shia villagers in the town of Dujail in 1982.
The murders came after an assassination attempt on Saddam for which the Islamic Dawa party of Nuri al-Maliki, the current Iraqi prime minister, claimed responsibility.
If convicted, the former Iraqi leader may be sentenced to death.
Al-Maliki has said that Saddam's execution cannot come soon enough.
In a televised message, he said: "We hope that the verdict will give this man what he deserves for the crimes he committed against the Iraqi people."
But he said that Iraqis should celebrate a guilty verdict in a way that "does not risk their lives".
A death sentence or life imprisonment generates an automatic appeal, which would delay any execution by months or possibly years.
"We hope that the verdict will give this man what he deserves for the crimes he committed against the Iraqi people"
Nuri al-Maliki, the Iraqi prime minister
In an interview with Aljazeera, Najeeb al-Nuaimi, a member of Saddam's defence team, said that he expected that Saddam would be sentenced to death.
He added that the defence team would appeal against the verdict despite the fact that it considers the court to be illegitimate.
Saddam is due back in court on Tuesday in another trial, for genocide against ethnic Kurds.
Baghdad went into total curfew overnight, as did Saddam's home province, including Dujail, and other areas where it is thought that Sunni Arabs could react to a guilty verdict.
Vacationing soldiers were recalled to duty and new checkpoints appeared on major roads.
"We warn anyone who intends to exploit this event that our response will be tough and severe"
Abdul Karim Khalaf, an interior ministry spokesman
Ali Abbas, a policeman, said: "We received orders to tighten security measures and to use any available policemen to tighten security."
Abdul Karim Khalaf, an interior ministry spokesman, said: "We warn anyone who intends to exploit this event that our response will be tough and severe."
A conviction could be a timely lift for George Bush, the US president, ahead of US midterm elections on Tuesday, when Republicans could lose control of Congress in a backlash over the Iraq war.
US officials have denied suggestions by Saddam's lawyers that the verdict was timed with the elections in mind.
Khalil al-Dulaimi, the head of Saddam's defence team, has called for the postponement of sentencing as he said that issuing a verdict on Sunday would help to bolster support for Bush ahead of the elections.
An interior ministry spokesman said that Iraqi police killed 53 suspected al-Qaeda fighters in a gunbattle on the southern outskirts of Baghdad on Saturday.
In another incident, mortar bombs killed eight people and wounded 25 in Baghdad's western Adhamiya district on Saturday night.
Baghdad police reported finding 15 bodies dumped throughout the city in the 24 hours ending at 6 pm on Saturday.