Wis. Stat. § 805.12
If the court can find as a matter of law that a party is causally negligent, contrary to the jury's answer, and the jury attributes some degree of comparative negligence to that party, the court should change the causal negligence answer and permit the jury's comparison to stand. Ollinger v. Grall, 80 Wis. 2d 213, 258 N.W.2d 693 (1977). If the answer to one material question shows that the jury answered perversely, the court should set aside the entire verdict unless it is satisfied that the other questions were not affected by the perversity. Fouse v. Persons, 80 Wis. 2d 390, 259 N.W.2d 92 (1977). When the verdict form did not contain a special fact question regarding the major issue of the case, real issues had not been tried. Schulz v. St. Mary's Hospital, 81 Wis. 2d 638, 260 N.W.2d 783. If evidence conflicts and inconsistent theories on the cause of the event are advanced, instructions on both theories should be given. Sentell v. Higby, 87 Wis. 2d 44, 273 N.W.2d 780 (Ct. App. 1978). An inconsistent verdict, if not timely remedied by reconsideration by the jury, must result in a new trial unless the party injured by the inconsistency waives the portion of its damage claim and the waiver does not result in a change of the prevailing party as found by the jury. Westfall v. Kottke, 110 Wis. 2d 86, 328 N.W.2d 481 (1983). Ambiguities in jury questions were "omitted issues" under sub. (2) and properly determined by the trial court. Badtke v. Badtke, 122 Wis. 2d 730, 364 N.W.2d 547 (Ct. App. 1985). A special verdict must cover material issues of ultimate fact. The form of a special verdict is discretionary with the trial court and an appellate court will not interfere as long as all material issues of fact are covered by appropriate questions. Industrial Risk Insurers v. American Engineering Testing, Inc. 2009 WI App 62, 318 Wis. 2d 148, 769 N.W.2d 82, 08-0484. The trial court cannot submit a case on one theory and resort to sub. (2) to dispose of it on another theory. Under s. 805.13(3), the parties confer, with the trial court's supervision, on the instructions and special verdict that will go to the jury. If a party has an objection, he or she must voice it or it will be waived. If the special verdict leaves out an essential material issue of ultimate fact of a cause of action pled and presented to the jury, and the jury's answers define, by necessary implication, what the missing issue should be, then, under sub. (2) the trial court may "fill in" this missing issue. But the trial court cannot "fill in" a missing cause of action. Hansen v. Texas Roadhouse, Inc. 2013 WI App 2, 345 Wis. 2d 669, 827 N.W.2d 99, 10-3137. Special verdict formulation in Wisconsin. Decker and Decker, 60 MLR 201 (1977). Product liability verdict formulation in Wisconsin. Slattery et al. 61 MLR 381 (1978).