Jockey David Walker has been found guilty of not giving his horse every chance to win a race in which he'd already bet on a rival.

Walker, 38, had already admitted the charge of betting on a rival horse, St Ransom, but denied not riding his own horse Watch Your Man on its merits in a race at Awapuni on August 16.

A judicial committee of Murray McKechnie and Noel McCutcheon said he could have done more aboard Watch Your Man after a hearing at Trentham racecourse on Thursday.

McKechnie said evidence suggested Walker failed to give his horse adequate opportunity to improve mid-race, and should have ridden more vigorously in the home straight.

A charge for not riding his horse Lil Mer on its merits at Waverley on July 31 was dismissed.

Walker will receive his penalty at a follow-up hearing on Friday.