Halle Berry Custody Trial Olivier Martinez To Testify

Halle Berry has a secret witness she's going to call to the stand to support her bid to take Nahla to Paris -- her fiance, Olivier Martinez.

Sources close to the case tell TMZ ... Halle's lawyer will ask Martinez -- a famous actor -- about his experience with paparazzi in Paris.  Martinez will say the photogs are far more respectful and less aggressive in gay Paris than their counterparts in the US of A.

Martinez will also discuss their living arrangement and his involvement with Nahla. He will also tell the judge that Halle is a class A mother.

As for how the case is going, we're told baby daddy Gabriel Aubry is having trouble making his case.  On Thursday, one of Halle's expert witnesses left the courthouse early without even testifying -- he was there to counter one of Gabriel's experts, but there was no need for a rebuttal because sources connected with Gabriel tell TMZ ... his expert kinda crashed and burned.
See also

    Halle Berry Hearing -- Paramedics Rush into Courtroom
    Gabriel Aubry -- Halle Berry Could Die Like Princess Diana
    Halle Berry's Paris Bid -- You Be the Judge