Section 685.4 - Procedure - statute of limitations1. A subpoena requiring the attendance of a witness at a trial or hearing conducted under this chapter may be served at any place in the state, or through any means authorized in the Iowa rules of civil procedure.2. A civil action under this chapter may not be brought more than six years after the date on which the violation of section 685.2 is committed, or more than three years after the date when facts material to the right of action are known or reasonably should have been known by the official of state charged with responsibility to act in the circumstances, but in no event more than ten years after the date on which the violation is committed, whichever occurs last.3. If the state elects to intervene and proceed with an action brought under this chapter, the state may file its own complaint or amend the complaint of a qui tam plaintiff to clarify or add detail to the claims in which the state is intervening and to add any additional claims with respect to which the state contends it is entitled to relief. For statute of limitations purposes, any such state pleading shall relate back to the filing date of the complaint of the qui tam plaintiff who originally brought the action, to the extent that the claim of the state arises out of the conduct, transactions, or occurrences set forth, or attempted to be set forth, in the prior complaint of that person.4. In any action brought under section 685.3, the state shall prove all essential elements of the cause of action, including damages, by a preponderance of the evidence.5. Notwithstanding any other provision of law, the Iowa rules of criminal procedure, or the Iowa rules of evidence, a final judgment rendered in favor of the state in any criminal proceeding charging fraud or false statements, whether upon a verdict after trial or upon a plea of guilty or nolo contendere, shall estop the defendant from denying the essential elements of the offense in any action which involves the same transaction as in the criminal proceeding and which is brought under section 685.3.