AEG says it was Jackson who hired Dr.
Murray is serving jail time for his involuntary manslaughter conviction.
Katherine Jackson is not the first family member to testify in the months-long trial, but the family matriarch may be among the most anticipated witnesses.
Two of Michael Jackson's nephews have also testified, including TJ Jackson, who shares guardianship with his grandmother over the King of Pop's children.
Katherine Jackson has spent much of the trial seated in the front row of the courtroom, where she has been well-received by her son's fans who also routinely watch the proceedings.
On a recent day, some of the fans lined the hallway as Katherine Jackson walked to the elevator, flanked by her nephew, Trent, and security.
The fans waved as the matriarch moved slowly past.
"We love you. We love Michael so much," they said, blowing kisses.
She lifted her hand to wave before leaving.