O'Neal is heading to trial to fight University of Texas officials who claim the silkscreen, which is valued at around $30 million (£20 million), is rightfully theirs, claiming that Fawcett left her entire art collection to the institution following her death in 2009.
The piece is one of two Fawcett portraits by Warhol - one is hanging in the university's gallery, while O'Neal claims the disputed picture was given to him by the artist, who was a close friend.
During his deposition, the Love Story veteran revealed that Fawcett had taken his version of the painting in 1998, a year after she caught him in bed with another woman. He admitted to retrieving the artwork following his longtime partner's passing in 2009 and placing it in his Malibu, California home.
The case is due to be heard in a Los Angeles court this week (begs11Nov13), and the late actress' Charlie's Angels co-star Smith has been listed on the witness list.
O'Neal is also due to testify, as is his son with Fawcett, Redmond, and the former couple's photographer pal Alana Stewart.