Lawyer Abdel Haq Alani told the BBC the former president will challenge the legality of the special tribunal, due to open inside Baghdad's fortified Green Zone on 20 October.
"He had full immunity under the prevailing Iraqi constitution and you cannot have a retroactive legislation that removes that immunity," Alani said in an interview late on Thursday.
Iraqi officials say the only charge against Saddam so far is the killing of more than 140 men in the mostly Shia village of Dujail after a failed 1982 assassination attempt against him.
Alani said the defence will argue that those killed had been found guilty under Iraq's laws and Saddam's only role was to sign their death warrants.
"These people were tried and found guilty and sentenced to death according to the Iraqi criminal code," Alani told the BBC.
Alani, who told reporters in September that Saddam had been denied his legal rights, said he still thought the former Iraqi president would not have a fair trial.
"He had full immunity under the prevailing Iraqi constitution and you cannot have a retroactive legislation that removes that immunity"
Abdel Haq Alani,
Saddam Hussein's lawyer
"A fundamental element of having justice is to see that there is a fair and impartial trial," he said. "That I think is not happening in Iraq now."
Despite concerns about the trial, Alani said Saddam had a positive outlook.
"He is in high spirits and is very defiant," Alani said. The BBC said Saddam's defence team has just received an 800-page bundle outlining the prosecution case.
The report said many of the pages they have been sent are unreadable and they still have no charge details.
Saddam, who has been held by US forces since they captured him in 2003, sacked his defence team in August to bring in a more professional group.
Alani, an Iraqi-born barrister, has assembled a legal team with Khalil Dulaimi, who is based in Baghdad and is the only lawyer who has so far been allowed to meet Saddam.