SAN FRANCISCO — Overruling a 78-year-old precedent, the California Supreme Court on Monday made it easier for parties to a written contract to claim it was tainted by fraud.

The unanimous decision in Riverisland Cold Storage v. Fresno-Madera Production Credit Association overrules Bank of America v. Pendergrass and relaxes the rules for parol evidence in California. It will give a Tulare County couple a chance to prove that a loan agreement they signed differed from the one allegedly promised them orally by a credit association vice president.