Britney Spears' well-publicized breakdown in which she shaved head and accosted paparazzi with an umbrella was caused by drugs, according to an attorney for her former manager.

"She liked to use amphetamines, speed or uppers … and most of the things that went wrong were related to that drug," attorney Joseph Schleimer said in a Los Angeles courtroom Thursday where his client, Sam Lufti, is suing Spears, 30, and her family, according to the Associated Press.

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Lufti, 38, was once the pop superstar's manager and closest confidante, coming to her side in 2007 as her world began to unravel and, later, spurring one of Spears' most public meltdowns after an argument left her sitting barefoot on a curb outside her home, sobbing as surrounding paparazzi caught it all on tape.

Lufti, a sometime film producer, is now seeking a share of the multimillion-dollar fortune of Spears, who earlier this month was named by Forbes as the second-highest paid woman in Hollywood. Lufti says he had an agreement to earn 15 percent of her earnings as her manager.

"My client was made a scapegoat for drug abuse and erratic behavior of Britney Spears," Schleimer told jurors on the trial's opening day. "He was terrified of being her manager when she overdosed."

Spears' fortune has been under a conservatorship headed by her father, Jamie, since her public breakdown four years ago. She lost custody of her two sons, Sean and Jayden, to ex-husband Kevin Federline in 2008 before regaining custody of both boys in 2011 as she made a professional and personal comeback.

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Lufti is also suing Spears' conservatorship and Spears' mom, Lynne Spears, saying that Lynne Spears' 2008 book, "Through the Storm," made libelous claims about his role in Spears' life and that he, Lufti, was a key player in Spears' 2007 album "Blackout" and therefore has claim to the earnings.

Spears, 30, was not at the courtroom Thursday but her parents were in attendance to see Lufti's attorney flash many unflattering images of her during the meltdown.

"Most of the things that went wrong related to that habit," Schleimer said of Spears' alleged drug use, according to People. "My client sometimes spent 24 hours a day to prevent Britney from using drugs."

Attorneys for Spears' parents and conservators were scheduled to make their opening statements today in the case that first began when Lufti sued in 2009.

The heated courtroom drama comes as Britney Spears' personal drama appeared to be settling down with an engagement to her manager, Jason Trewick, and a steady gig judging "The X Factor" on FOX.

Calls made to a representative for Spears and her attorney, Joel Boxer, were not returned as of this writing.

The Associated Press contributed to this report.