The suspension of the in-form Walsh is a blow to the Maroons' hopes of sealing a rare series whitewash in Sydney on July 12 and pits Hamiso Tabuai-Fidow and AJ Brimson against one another in a battle for the coveted fullback jersey.
Walsh's predecessor Kalyn Ponga has already ruled himself out of the Origin series to focus on club duties with Newcastle.
The incident took place in the 74th minute of the Broncos' loss to Gold Coast on Sunday and led the NRL to refer Walsh directly to the judiciary on a contrary conduct charge.
On-field microphones recorded Walsh yelling "What the f*** do you mean, c***?" directly after Butler blew an obstruction penalty.
But on Tuesday night the defence's case rested on the claim he had actually been addressing teammate Patrick Carrigan.
Walsh said Carrigan had approached him and told him to "slow your f***ing brain" so as not to give away more penalties, to which Walsh reacted with the profanity.
After a hearing that lasted two hours and 40 minutes on Tuesday night, the two-man judiciary panel of Penrith great Tony Puletua and Sean Hampstead deliberated for an hour and was unable to reach a unanimous verdict.
Judiciary chair Geoffrey Bellew SC cast a deciding vote as to Walsh's guilt and was satisfied on the balance of probability Walsh had been addressing Butler and not Carrigan.
The NRL's counsel proposed a ban of four matches, with Walsh's defence suggesting a one-game suspension, before three was reached.
The fullback will miss Saturday's clash against the Dolphins, Origin III and the clash with Canterbury in round 20.Â
