John Prentis (plaintiff) injured his hip when a forklift he was using caused him to fall. The forklift was manufactured by Yale Manufacturing Co. (Yale) (defendant). Prentis and his wife (plaintiffs) brought suit, claiming among other things that the forklift was defectively designed because it had no seat or platform for the user. Prentis's counsel requested jury instructions on the theories of negligence and breach of implied warranty, but the trial court combined the implied-warranty and negligence theories into a unified jury instruction. The jury found in favor of Yale, and Prentis appealed. The appellate court reversed, holding that the trial court's failure to give the requested implied-warranty instruction was reversible error and required a new trial. Yale appealed to the Michigan Supreme Court.