Mikos shot Brannon to death to prevent this testimony, and could be facing the death penalty. Mikos' lawyers may provide testimony from mental health experts to help him avoid the death penalty. Mikos was also found guilty of fraud by a federal grand jury.
A foot doctor was convicted Thursday of murdering a patient to keep her from telling how he cheated Medicare.
Dr. Ronald Mikos, 56, could get the death penalty.
The penalty phase of his trial is scheduled to begin Tuesday.
The federal jury also found the Chicago podiatrist guilty of swindling Medicare by billing it for thousands of foot operations he never performed.
Mikos was accused of shooting to death patient Joyce Brannon in 2002, days before she was supposed to testify against him before a federal grand jury.
The woman was expected to say that 72 operations Mikos had claimed he performed on her never happened.
Mikos' lawyers have indicated they might introduce testimony from mental health specialists during the penalty phase to try to save Mikos from execution.