Debbie Rowe is the biological mother of Jackson's 15-year-old daughter Paris and 16-year-old son Prince. She married Jackson in 1996 and they divorced in 1999.
Jackson's family is suing AEG Live for allegedly failing to properly supervise Dr. Conrad Murray, the personal physician hired to care for Jackson as he prepared for a string of comeback shows in London.
Murray is serving a four-year prison sentence for involuntary manslaughter for administering lethal amounts of sedatives and anesthesia to Jackson in an effort to help Jackson sleep. The pop star was 50 when he died in 2009.
TMZ said Rowe is expected to testify Tuesday or Wednesday that Jackson secretly abused prescription drugs for decades leading up to his death.
She also will likely tell the court she believes her former boss, dermatologist Dr. Arnie Klein, frequently gave Jackson drugs via injection up until days before he died.
In addition, Rowe is expected to testify that no one in Jackson's life -- except for her -- ever said "no" to the singer, TMZ reported.