Oksana's Tape Expert Claims No Monkey Business

4/24/2011 11:15 AM PDT

Oksana Grigorieva Angry at Mel Gibson for Claiming Tapes are Edited and Audio Expert Kent Gibson Says In Declaration that Recordings on her Computer are Unedited

TMZ has gotten hold of Oksana Grigorieva's ammo in her war with Mel Gibson over whether her secret recordings were edited ... and O.G.'s expert claims they're the real deal.

TMZ has obtained a declaration Kent Gibson, a forensic audio expert who examined the 18 recordings from Oksana's computer -- 9 are voicemails from Mel and 9 are recorded conversations between Mel and Oksana.  By the way, check out the times the various calls were made -- interesting.

In his declaration filed in the family law case and obtained by TMZ, Kent says, "In my professional opinion as a forensic audio examiner, I conclude that the recordings have not been modified, and can be considered authentic."

Oksana is pissed at Mel for saying the tapes were edited.  However, in Mel's interview with deadlinehollywood.com, when Mel talks about edited tapes, he appears to be referring to the tapes that were leaked in the media.  In other words, it's possible the recordings in Oksana's computer are pristine but they were later edited before going online.