Porn star Janine Lindemulder's lawyer plans to call the Oscar winner as a witness to a hearing in the custody case on 21 October (10).
Richard Masson tells Life & Style magazine the hearing will address issues relating to the financial and physical care of Sunny, and his client feels sure that Bullock can help her win the latest round in her battle against James.
Lindermulder tells the publication, "People say, ‘What does Sandra have to do with it?’ She has a huge part in this."
Bullock and James won full custody of Sunny when Lindermulder was jailed on tax evasion charges in 2009.
But the adult actress has been battling to spend more time with her daughter ever since she was released from jail and she ramped up her efforts earlier this year (10) when James and Bullock's marriage fell apart.