Flowers v. Diamond Shamrock Corp.

The Flowers (plaintiffs) leased mineral rights to Diamond Shamrock (defendant), which paid royalties based on a below-market contract price rather than actual market value, sending checks marked as full settlement of the account. After the Flowers declined Shamrock's offer to formalize the lower contractual rate and instead demanded the market-rate difference, Shamrock insisted it would continue paying under the existing lease terms, and the Flowers kept cashing the monthly checks for several more years before suing for the shortfall; Shamrock argued the Flowers' repeated endorsement of the checks constituted accord and satisfaction, and the trial court granted Shamrock judgment notwithstanding a jury verdict for the Flowers.