The former Illinois attorney general appointed to President-elect Barack Obama's Senate seat once drew heavy criticism for his decision to pursue the death penalty for a defendant who was later acquitted.
Cruz was twice convicted, but by 1992 another man -- a repeat sex offender -- confessed to the crime, and in 1995 DNA evidence ruled out Cruz as the rapist and implicated the sex offender.
ProPublica, a nonprofit news outlet, reported that Burris' own deputy attorney general, Mary Brigid Kenney, pleaded with Burris to drop the case at the time. She resigned, writing in her resignation letter that Burris was ignoring evidence and that she felt she was "being asked to help execute an innocent man."
Burris reportedly said at the time that it was not his role to "place my judgment over a jury."
But Cruz eventually was granted a new trial and was acquitted after spending 11 years on death row.
Burris was appointed to the U.S. Senate on Tuesday by Illinois Gov. Rod Blagojevich, who has been charged by federal prosecutors with trying to sell the seat to the highest bidder. U.S. Senate leaders have said they would not seat Burris.