We broke the story Friday ... the L.A. County Sheriff's Department is in possession of at least one email from Oksana to Mel, in which she clearly states Dalton physically abused her.
But Oksana told us yesterday ... "Any implication that he [Dalton] ever struck me is untrue."
We also know ... during the time Oksana was with Mel, she complained that Dalton wasn't paying enough child support and went to two lawyers to get more -- though she claims it was all Mel's idea.
Now here's the problem. If Gibson is prosecuted for domestic violence, his lawyers can use the email to argue she made up the claim against Dalton, around the same time she wanted more money from him.
That's precisely the same M.O. Gibson's lawyers will argue to the jury -- that Oksana lies to rake in money.