She says she deserves a new trial because of it.
In court papers filed Wednesday, Stewart's lawyer says juror Chappell Hartridge concealed a 1997 arrest for assault, and a string of civil judgments against him.
Hartridge was also the first juror to speak to reporters after Stewart was convicted. He called the verdict a victory for the small investor.
Stewart's lawyer says those comments showed bias against her.
The U.S. Attorney's Office says it's studying the motion.
Stewart is likely to get about a year in prison when she's sentenced June 17.
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