Does the prosecution or the defense have a burden to determine whether misconduct by below defendant in a civil case affect or might affect the fairness of the trial?

The truth is that below defendant never claimed that the misconduct by itself affected or might affect the fairness of his trial. We do not have to decide who--the prosecution or the defense--would have what burden if defendant had created an issue on the question whether the prosecution's peek into his mail directly or remotely hampered the defense effort or made it more easily rebuttable. (Cf. Alderman v. United States, 394 U.S. 165, 183, 89 S.Ct. 961, 22 L.Ed.2d 176.) The only relief defendant asked from the trial court was suppression, which is precisely the relief that he got. No error, therefore, appears.