During a review of a company's procurement process, an IS auditor is evaluating several pieces of evidence to support a finding about unauthorized purchase orders. The auditor has collected: (1) a system-generated exception report produced by the auditor using the ERP database, (2) a verbal confirmation from the procurement manager, (3) a screenshot of the approval screen emailed by an accounts payable clerk, and (4) a signed policy document provided by the vendor. Which piece of evidence should the auditor consider MOST reliable?