Caitlyn Jenner will not be prosecuted for vehicular manslaughter in February's fatal PCH car crash, but there's one string attached, TMZ has learned.

Well-placed sources connected with the L.A. County D.A.'s Office tell us, the people assigned to review the case have determined Jenner's conduct was negligent, but not criminal. We're told the people making the decision are also relying on the L.A. County Sheriff's Dept., which investigated and came up with the same conclusion.