Sheriff's Dept. Hones in on Oksana's Deal

7/28/2010 3:50 PM PDT

Sheriff's Dept. Hones in on Oksana's Deal

Law enforcement sources tell TMZ the L.A. County Sheriff's Department is inquiring about the $15 million deal Oksana Grigorieva struck with Mel Gibson during their mediation -- and the mediation is relevant both for Oksana's domestic violence claim and Mel's extortion claim.

Sources say Sheriff's investigators are interested in both the evidence presented during the mediation and the evidence that is notably absent.

For example, there are now reports that Oksana claims to have photographic evidence of a black eye following the Jan. 6 fight. Sources involved in the mediation tell TMZ Oksana never mentioned a black eye nor did she present photos to anyone connected to the mediation. The black eye issue was never raised in any form whatsoever, sources tell TMZ.

Furthermore, we're told, the tapes were the 800-pound elephant in the room that led to the $15 million agreement -- which Oksana later disavowed. 

As one source connected with the mediation said, "Oksana and her lawyer pulled out all the ammo they had that would embarrass Mel, and now things are surfacing after the fact that call her credibility into question."

We're told Sheriff's investigators are looking at the mediation both to evaluate Oksana's credibility and to determine if there is evidence of extortion.