Los Angeles: She is a chart-topping artiste with millions in the bank but Britney Spears` parents have claimed that she is "mentally incapable" of testifying in a court case against her mother.
The popstar`s mother Lynne is being sued for defamation by Spears` ex-manager Sam Lufti over claims made about him in her tell-all memoir, `Through The Storm`.
She alleged that he regularly drugged Spears and harassed her following her well-publicised breakdown three years ago.
When Lufti requested that Spears be called as a witness to testify in the case, Lynne claimed that her 29-year-old daughter is incapable of doing so, according to a website.
The singer remains under the conservatorship of her father, Jamie Spears, and her lawyer, Andrew Wallet.
Both are unwilling to let Lufti have contact with Spears, who they say is in a "fragile mental state". But Lufti has rejected their claims, arguing that Spears is now back in control of her mental health.
According to the magazine, Lufti has had an expert in psychiatry analyse a recent video interview with the singer in support of his argument.
"In the Ryan Seacrest interview, which was recorded approximately two months ago, Britney Spears is interviewed at length, and she responds logically and coherently to
questions, evidencing logical thinking and mental competency," Lufti told the court.