Cook County Judge Michael Toomin has appointed former US Attorney Dan Webb to investigate the case.
Smollett told police in January that two masked men threw a noose around his neck and poured chemicals on him while yelling racist and homophobic slurs and expressing support for US President Donald Trump.
Webb won a conviction of one of former US president Ronald Reagan's advisers for his role in the 1980s Iran-Contra scandal, and now serves as co-executive chairman of one of Chicago's largest law firms.
Toomin said Webb was "guided by a strong moral compass and integrity".
Webb said he intends to request a special grand jury to hear evidence on whether any people or offices previously handling the case had committed wrongdoing and whether there are further grounds to prosecute Smollett.
Smollett has denied staging the attack.
A month after Smollett made the allegation, Cook County State's Attorney Kim Foxx charged him with filing a false police report and accused him of paying $US3500 ($A5000) to two men to stage the attack to generate public sympathy.
In March, to the shock and dismay of local politicians and police officials, Foxx's office dropped the charges, saying an agreement by Smollett to forfeit his $US10,000 ($A14,800) bond was a just outcome.
Smollett was written out of the final two episodes of Empire this season after he was charged with staging the hate crime.