David Emerson Nickels appeared in Grant County Superior Court on Tuesday and remains jailed on $5 million bail.
He was arrested in Helena last week and is accused of killing 35-year-old Sage Munro in Ephrata, Wash., on Dec. 29. Munro, who was dating Nickels' ex-girlfriend, was found dead from a single gunshot to the chest. Nickels and the woman had been secretly still seeing each other.
Court records say Nickels told investigators and friends he was in Great Falls at the time of the slaying, but cell phone records showed his phone registered a call from a cell tower in Spokane about two hours after the shooting.
He was extradited to Washington on Thursday.