When two (2) or more counties are joined for judicial purposes, the expense of the trial of a cause must be paid by the county where the offense is alleged to have been committed.
Idaho Code § 19-2210
Expenses to be paid by what county
Current official text: Idaho Statutes (Idaho Legislature). Digitized from the UniCourt Code Improvement Commission public-domain capture. Reproduced from public-domain Idaho statutes; confirm against the official source for the current text. Not legal advice.