Walton, worth $6.3 billion and listed by Forbes magazine as America's second-richest woman--behind her mother--could have simply paid $650 to settle the case but chose instead to fight the charges with a pair of attorneys.
Walton, 48, frowned slightly as the judge's decision became apparent, but she later said she had no regrets about the trial.
Walton, daughter of Wal-Mart Stores Inc. founder Sam Walton, crashed her car Jan. 27 near her home. She broke her nose when her car hit a gas meter and a telephone box. Walton testified that she had had a few drinks but wasn't drunk.
Her attorneys argued that the crash could have been caused by fatigue after a full day of business meetings.
Police officers testified that Walton repeatedly refused to submit to a blood-alcohol test.
"She turned back to me and said, 'Do you know who I am? Do you know my last name?' " Police Officer Charles Motsinger testified.
Walton said she did not recall making those statements but said, "Officer Motsinger was very ugly to me."
After she was released by police, Walton returned to the hospital and requested a blood test. A hospital worker said Walton's blood-alcohol level registered 0.16. The legal limit in Arkansas is 0.10.
Municipal Judge Stanley Ludwig found Walton guilty of driving while intoxicated, refusing to take a blood-alcohol test at the request of police, driving without a seat belt and failing to properly maintain control of her vehicle.