The trial, for the killing of dozens of Shia villagers at Dujail in 1982, will therefore be starting just a few days after a referendum on a new constitution.
The source, who is not attached to the Special Tribunal trying the deposed president and his aides for crimes against humanity, forecast a quick trial and execution.
"After what he did, how can we not execute him?" he said.
On Thursday, Iraq hanged its first three criminals since Saddam was overthrown in 2003 and officials in the Shia-led government have made clear they want a death sentence for the man they blame for the deaths of many thousands.
The trial may stir passions among some minority Sunni Arabs, who dominated Iraq under Saddam and before. In some demonstrations this past week against the new constitution, his face has reappeared in public, on placards and posters.
For that reason, the timing of the trial has been sensitive; judicial officials indicated last month that the Dujail hearings would be ready to begin by the beginning of October, so the choice of 19 October appears politically driven to avoid it clashing with the referendum campaign.
The referendum is due to take place by 15 October and the Electoral Commission, which will set the exact date shortly, has said it is likely to be on or very close to the 15th.
Officials from the Special Tribunal which is trying the deposed Iraqi leader and his associates for crimes against humanity declined comment. They have in the past complained that government leaders were pre-empting their statements.
Officials say the trial will not run into years or anything like the time former Yugoslav president Slobodan Milosevic has been before the international court at The Hague.
Weeks rather than months, was a forecast by one official involved in the process. He also said recently it was possible that Saddam might be executed if convicted only of the killings at Dujail, so that further trials for mass murder against Kurds and Shias and other offences might never take place.
Prosecutors have said Saddam's direct responsibility for the deaths may be easier to prove. The case involves the deaths of possibly more than 140 men from the village, north of Baghdad, where Saddam survived an assassination attempt in 1982.
The trial, which officials have said will probably largely be televised, will be held in a specially prepared building inside the fortified Green Zone government compound which was once Saddam's presidential palace complex on the Tigris.