If the design of a product or product component is in issue in a product liability action, the design shall be presumed to be reasonably safe unless, at the time the product left the control of the manufacturer, a practical and technically feasible alternative design was available that would have prevented the harm without significantly impairing the usefulness, desirability, or marketability of the product. An alternative design is practical and feasible if the technical, medical, or scientific knowledge relating to safety of the alternative design was, at the time the product left the control of the manufacturer, available and developed for commercial use and acceptable in the marketplace.
735 ILCS 5/2-2104