We're told Birkhead will testify either Thursday or Friday. Prosecutors will ask Anna's baby daddy about various comments he made about Howard K. Stern allegedly fueling Anna's drug habit.
But here's the problem ... Birkhead made these comments to TMZ and other media outlets during the time he was at war with Howard over Dannielynn.
Birkhead and Stern have not only settled their custody dispute and other differences ... they actually work together in handling all matters Anna Nicole.
So Birkhead is in an awkward position ... how does he back off his statements? Even more awkward, perhaps ... the prosecution is calling a witness who probably will not own the statements they're calling him to the stand to make.
The three defendants -- Howard K. Stern and two of Anna's doctors, Dr. Sandeep Kapoor and Dr. Khristine Eroshevich -- have all pled not guilty to a grand total of 23 felonies.
Stay tuned ...