Which the court must ascertain the truth or falsehood to before rendering judgement; which given the information the court has on hand, would be dangerous ground for a lawyer to tread upon in this case.

At the most; a prudent judge would likely allow it while the case is still being tried. You'd have to deal with defamation only after the completion of the criminal probe, where a suit could be levied under the auspices of "we were deemed innocent".

IANAL, and this is assuming American court procedure; things may be different in Germany.