'Profiteering' allegations
Critics say the present government is punishing him for refusing to testify against his former president.
"The Iraqi government also wants to avoid the public criticism for keeping an ailing man in prison for five years without presenting any charges against him," Aziz's son, Ziad, said in a telephone interview from Jordan.
The merchants were rounded up over two days in July 1992 from Baghdad's wholesale markets.
They were charged with manipulating food supplies to drive up prices at a time when many Iraqis were suffering economically.
All 42 of them were executed hours later after a quick trial and their bodies were returned to their families the following morning.
Relatives of the men deny allegations that they were manipulating prices.
Some believe that they were killed because their power to set prices during sanctions meant they posed a threat to the Saddam regime, Owen Fay, Al Jazeera's Baghdad correspondent, said.
Others say that members of the ruling Baath Party wanted to control the market and had the businessmen killed to remove any competition.
Execution orders
Aziz's co-defendants include Saddam's half brother, Watban Ibrahim al-Hassan, who was interior minister at the time, and cousin Ali Hassan al-Majid, also known as "Chemical Ali", who has been sentenced to death in another case.
A judge with the Iraqi High Tribunal, who declined to be identified, said the charges against the defendants would include war crimes, crimes against humanity and genocide.
If convicted, the men could face death by hanging.
The judge said Aziz was being prosecuted because he signed the execution orders against the merchants as a member of Saddam's Revolutionary Command Council.
Aziz's lawyer has said the charges against his client are "baseless".
"There us no credible accusation against Aziz," Badia Arif, Aziz's lawyer told reporters.
"The prosecution assumes that just because he was a member of the Revolutionary Command Council, which carried out the death sentences, he is guilty," Arif said.