Saddam, 68, boycotted the previous court session after telling judges to "go to hell", but has appeared in the dock for Wednesday's session.
The trial was adjourned for the general elections to elect the first full-term government since Saddam's repressive Baathist regime was toppled from power by the 2003 US-led invasion.
Saddam and seven of his associates are being tried over the killings of 148 Shi'ites from the village of Dujail in the early 1980s after the former head of state was targeted by an assassination attempt at the village.
The court is expected to hear testimony from about five witnesses before being adjourned until next month to make way for election results, holidays and the Hajj pilgrimage, although there may be another hearing on Thursday.
Witnesses, many hidden behind screens with disguised voices, have relayed chilling tales of torture while Saddam and his co-defendants loudly disputed their testimony and condemned the court.
Saddam faces the death penalty if found guilty.
The trial marks the first time a Middle Eastern head of state is being tried by his own people.
Saddam has remained defiant throughout the trial so far, refusing to acknowledge he is no longer the Iraqi leader and demanding better treatment by his captors.
Prosecutor Jaafar al-Mussawi earlier told AFP that the defence would present 40 witnesses, including three ministers from the former regime and other people being detained by US forces in Iraq.
But the defence has denied Mussawi's remarks as "totally untrue," saying it does not recognise the court, and is threatening to boycott the trial because of inadequate security assurances.
Death threat for lawyer
Defence lawyer Najib al-Nuami said on Tuesday that he had been threatened with death at Baghdad airport and that he would present a petition for better security during Wednesday's session.
"Today was threatening, tomorrow will be a weapon," he told AFP.
Two defence lawyers have already been assassinated since the trial began on October 19.
Fellow defence lawyer, former US attorney general Ramsey Clark, has not returned to Baghdad out of security concerns, said Nuami, a former Qatari justice minister.
Instead, court sources said Curtis Doebbler, a US attorney, would ask to stand in his place at Wednesday's session.
Hearings have been often chaotic, although chief judge Rizkar Mohammed Amin has been gradually asserting more control over rambling witnesses and noisy defendants.
Even on the day Saddam did not appear, his mantra was taken up by his half brother Barzan al-Tikriti, who ridiculed witnesses for not getting their facts straight and then complained loudly about the conditions of his detention.
There are reports that during a closed session after Saddam's furious tirade on December 6, he apologised to the judge for his behaviour and asked to be excused from the next session in order to save face.
Clark and Nuami, a former Qatari minister of justice, have challenged witness testimony as confused, fabricated and not directly implicating their clients.