"Mr Jethmalani said in court that the girl is mentally disabled and not fit," public prosecutor Anand Purohit said after a Jodhpur court rejected the guru's bail plea.
But he added that the senior lawyer did not produce any evidence to support his contentions.
The high court in Rajasthan will now hear his plea for bail on Wednesday. The 75-year-old godman has been in jail since September 2.
Earlier, the teen complainant's lawyer had alleged that the family had faced death threats from Asaram's followers and phone recordings of the threats would be given as evidence to the court.
"The father of my client says they are constantly facing death threats. He mailed me an audio clip in which it is very clear that Asaram's followers are threatening them and intimidating witnesses. The family feels unsafe," said Manish Vyas, the girl's lawyer.
The teenager, who used to live in Asaram's ashram in Madhya Pradesh's Chhindwara district, has accused the guru of forcing himself on her at his ashram in Jodhpur, and threatening to kill her and her parents if she reported him.
The godman's aide Shiva, who is reportedly a key witness in the case, is also in judicial custody. He is accused of taking the girl to Asaram Bapu on August 15. The guru had allegedly told the girl's parents that he would exorcize her of evil spirits.
The religious preacher has denied the allegations of sexual assault and told the police he met the girl and her family as part of a large gathering that came for his 'satsang' or discourse on August 15.