Saddam Hussein's (search) lawyers plan to challenge the legitimacy of the tribunal set to try him in Iraq and argue that he is immune from prosecution for alleged crimes he committed as president, one of his lawyers said.

The tribunal "was drafted by an occupying power," Abdel-Haq Alani, an Iraqi-born lawyer involved in Saddam's defense, told the British Broadcasting Corp. in an interview aired Thursday night. "It has no right under international law to change the legal system of the occupied land."

He said Saddam was feeling "upbeat" and "very defiant" about the trial, scheduled to start Wednesday.

The case centers on the role he and his co-defendants played in a 1982 massacre of 143 people in Dujail (search), a mainly Shiite Muslim town north of Baghdad, after a failed assassination attempt on Saddam.

Alani showed the BBC a list, signed by Saddam, of the 143 people killed, and said the leader had simply signed off on sentences handed down by the court system.

"These people were tried and found guilty and sentenced to death according to the Iraqi criminal court, ... then the president signed the death sentence," he said.

The BBC said the legal team compared the signatures to President Bush's affirmations of criminals' death sentences when he was governor of Texas.

Alani told the network that the defense team also planned to argue that Saddam should be immune from prosecution because his alleged crimes were committed while he was head of state.

"He has full immunity under the prevailing Iraqi constitution," the lawyer said. "You can't have retroactive legislation that removes that immunity."

The office of Anthony Scrivener (search), a leading British lawyer, said Friday he had been asked to help defend Saddam.

Scrivener, who once helped free four men wrongfully imprisoned as Irish Republican Army bombers, had not yet decided whether to take the job, said Martin Hart, senior clerk in Scrivener's office.

Scrivener, 70, was part of the legal team that freed the "Guildford Four," jailed for two 1975 pub bombings.

Desmond Doherty, a Northern Ireland-based lawyer who worked on the inquiry into the "Bloody Sunday" killings, said he had also been approached about joining the team.

"The arrangements in respect of this are in hand and it is hoped they will be finalized very soon," Doherty said in a statement.