Carol Layfield, as guardian for her son Michael, brought suit against the Department of Transportation DOT and Everett Dykes Grassing Company Dykes. She alleged negligence in the construction and resurfacing of a road where Michael Layfield lost control of a vehicle in a rainstorm and crashed into a tree. After discovery, DOT and Dykes moved for summary judgment. In opposition, Ms. Layfield presented the testimony of an expert who opined that . . . DOT had not originally constructed the road to proper sloping specifications in 1949 and that Dykes’s recent microsurfacing of the road in June 2001 contained irregularities that exacerbated the water accumulation problem. The expert further opined that Michael’s loss of control of his vehicle was caused by encountering the accumulated water on the road. Layfield v. Dept. of Transp. , 271 Ga. App. 806, 807 611 SE2d 56 2005. The trial court concluded that the expert’s conclusions were speculative, and granted summary judgment in favor of DOT and Dykes. On appeal, a divided Court of Appeals affirmed, with the majority holding that, because of the speculative basis of the expert’s conclusions, the trial court properly granted summary judgment . . . on the ground that no competent evidence showed a causal link between Michael’s losing control of his vehicle and the presence of the accumulated water on the roadway. Layfield v. Dept. of Transp. , supra at 808. Ms. Layfield applied for certiorari, which we granted in order to determine whether the Court of Appeals correctly held that the opinion of her expert as to causation was speculative and insufficient to withstand the motion for summary judgment.
1. Whether proximate cause exists in a given case is a mixed question of law and fact. It requires both factfinding in the “what happened” sense, and an evaluation of whether the facts measure up to the legal standard set by precedent. Ordinarily, both determinations are most appropriately made by a jury upon appropriate instructions from the judge. Cit. Atlanta Ob. & Gyn. Group v. Coleman , 260 Ga. 569, 570 398 SE2d 16 1990. Thus, “it is axiomatic that questions regarding proximate cause are ‘undeniably a jury question’ and may only be determined by the courts ‘in plain and undisputed cases.’ Cit.” Ontario Sewing Machine Co. v. Smith , 275 Ga. 683, 687 2 572 SE2d 533 2002.
