Where a defendant has entered a guilty plea, he may not later seek a certificate of innocence, because by entering the plea, he has voluntarily caused or brought about his own conviction.The 1st District Appellate Court affirmed the decision of Cook County Associate Judge Domenica A. Stephenson.In May 1993, Marshall Morgan Jr. was murdered. Wayne Washington and Tyrone Hood were arrested and charged with his murder and robbery. Washington went to trial, and the jury failed to reach a verdict, resulting in a mistrial. Hood …