Los Angeles- Two forensic experts testified Monday that a signature on a model release form involving topless photos of Cameron Diaz appeared to be forged using an autographed publicity photo of the actress.

The testimony came in the case against photographer John Rutter, who is accused of trying to blackmail Diaz over the topless pictures.

Rutter is accused of trying to sell the pictures to Diaz for $3.5 million before her film “Charlie’s Angeles: Full Throttle” was released. Diaz testified Thursday that Rutter told her if she didn’t buy the photos, taken in 1992 before she was famous, he could sell them for $5 million to buyers he said would use them to portray her as a “bad angel.”

Forensic document examiner Bruce Greenwood, who analyzed copies of Diaz’s writings, said he was certain the signature on a publicity photo of her and “Feeling Minnesota” co-star Keanu Reeves also was forged. Greenwood said he noted certain letters in Diaz’s name were “slanted completely different” from the handwriting samples he received from her.

Prosecutors said Rutter allegedly showed Diaz the release form when he tried to blackmail her and the actress said it wasn’t her signature.

Another forensic expert also testified Monday that he was positive Diaz’s signature was forged.

George Reis, who worked for the Newport Beach Police Department for 15 years, also said it appeared the publicity photo was used to make the forgery.

Rutter, 42, is charged with attempted grand theft for the alleged blackmail scheme, forgery for the signature on the form and perjury for declaring in a separate civil case that the signature was authentic. If convicted, he could face up to six years in prison. An extortion charge has been dropped.

The actress is also suing Rutter in civil court. A judge has issued a permanent injunction prohibiting Rutter from distributing the photos.