Ariz. Rev. Stat. § 44-1657
If in a prosecution it is a material issue whether or not the rules, regulations, by-laws or customs of an exchange or board of trade on, by or through which a contract or offer for future delivery was made, permitted such contract or transaction to be settled or closed by delivery or tender of any grade of the subject matter specified in the contract or transaction, other than the grade upon which the price was based in the transaction, or at any price other than the actual price for spot delivery of such other grade or grades, at the time and place of the delivery or tender, proof that the delivery or tender was made or offered or pretended to be made by, through or upon any exchange or board of trade constitutes a prima facie case for the state.
A.R.S. § 44-1657