"Do their best" does not mean "lie to the court." The defense does not have to turn over incriminating evidence that it does not intend to use, and lawyers can ethically and accurately enter a "not guilty" plea and argue that the prosecution has insufficient evidence available to prove guilt beyond a shadow of a doubt.
IANAL but I believe this is untrue. It would not be acceptable for a lawyer to represent to the court something that they have reason to believe is false.